Cattle Practice 8.2

CATTLE PRACTICE Preliminary analysis of claw horn lesion development in each group of heifers has shown no significant effect of management regime in the first two years (1994-96). However, there were significant differences in the third year (Figure 4). Lesion scores for autumn calving animals (calving October and November) irrespective of management regime, were significantly higher (worse) after calving (p<0.01) than the spring calvers (calving February and March) despite spring calvers having significantly higher scores at the time of calving (p<0.01). Analysis of lesion development has again shown the importance of recurrent severe claw horn lesions in consecutive lactations especially at the sole-heel junction and the adjacent white line area. BCVA 2000 In short, these various studies have shown that lameness, particularly if it is due primarily to claw horn lesions, is associated with a range of risk factors which include: calving and lactation, housing in cubicles, cubicle and building "comfort" and season (see Table 2). Finally, although not specified in the table, there is good evidence that the better educated the farmer and herdsman the less lameness! VOL 8 PART 2 Figure 4: Total lesion score in 1st lactation heifers low input (L1) or high output (HO) systems. 1994- 1997. 2.5 3 3.5 4 4.5 Log 10 (lesion score +1) This confirmed the findings of the previous study. It reinforced the need for careful management of heifers around the time of their first calving to minimise the risk of claw lesion development in the mature animal. Despite there being no statistically significant effect of management system overall on claw lesion development in the first calving heifers, lameness was significantly more prevalent in HO herd as a whole (i.e. particularly the older cows that have been in the herd for some time). We believe that the major reason for this was the greater time that the high input cows remain housed (roughly 25% longer each year)and the consequent increase in long-term challenge to the feet from this abrasive and corroding environment. Summary of risk factors for claw horn lameness These studies and others elsewhere have suggested that in herds using fully formulated and "balanced" diets concentrate input is not as critical as was once thought. Nevertheless there is evidence to support an increased risk with higher concentrate input and a reliance on wet grass silage (see Livesey 1999, Webster 1999, and Logue et al., 1999 in Appendix 1). From Offer et al 1999 Table 2: Some risk factors for claw horn lesions. Strong information Less strong information Some information calving/lactation/age Season (autumn is worst) Housing (cubicle/straw yard) Good foot trimming Concentrate input (& yield) Lying time Previous lameness forage growth cubicle comfort/ general building design foot bathing tracks/walkways biotin other behaviours rumen metabolites training stock care trace elements other vitamins It is also well recognised that good effective foot trimming can reduce lameness, as a result the "Dutch Method" has become widely used in the UK. TACKLING CLAW HORN LAMENESS A recent review of the available literature has shown that, despite the increasing focus of our research, we still do not fully understand the relative importance of these many risk factors and the way that they interact to produce the lesions that cause lameness in our dairy cows. Unfortunately we need this understanding to determine the best intervention strategies to reduce lameness (Hirst & French. Pers. Comm. 1999). Without a complete grasp of this it is difficult for researchers to give farmers very specific recommendations. However, we can summarise how we believe we should be tackling this problem. Limiting the extent of challenge Management of the dairy cow should be targeted at limiting the extent of challenge from the risk factors listed in Table 2. Calving and lactation, housing and environment (and their influence on behaviour) as well as season and inadequate foot-care (foot-bathing and trimming) are all major risk factors for this type of lameness. In order to limit the challenge from these factors farmers should restrict the number that can act at any one time. For example, calving and then immediately housing cattle in the autumn gives three simultaneous challenges. Our evidence shows that one should either calve cows earlier or later in the year. Furthermore, as already shown, it is especially important to limit challenge to the dairy heifer. We have evidence that running a separate heifer group can limit both claw, interdigital and digital lesions.

CATTLE PRACTICE Good cubicle comfort and adequate access to forage for these young animals are vital as both can affect standing times and so further challenge the foot. In addition there is also some preliminary evidence that the management of the young heifer during the rearing phase is also of importance (see Logue et al 1999 in Appendix 1). All the available evidence indicates that this last mentioned aspect can be limited by steady growth rates and training the animals to the various management regimes they are likely to encounter in later life. Finally, good foot-care particularly good foot trimming and regular foot bathing are very important in reducing lameness. Indeed there is good anecdotal evidence that poor foot trimming can precipitate problems. For this reason it is important that all who are doing foot trimming have attended a training course on foot care and stick to a standard technique. If, in the course of either routine or clinical trimming, they find a lesion that they think is beyond them they should not be frightened to ask for a second opinion. Finding the most cost-effective approach A major consideration in the these times of financial stringency is just how much will the intervention cost and what are the benefits likely to be for your farm? In Table 3, we try to give a simple guide to the cost of the various inputs that reduce lameness. Study of this may help in giving some priorities on how best to tackle lameness. BCVA 2000 In summary to reduce lameness obtain information about the extent of the disease on the farm determine what type of lameness is affecting the herd, relate it to the management and environment and strive to limit the number of risk factors faced by a dairy cow at any particular time. By using Table 3 the most costeffective changes that could be utilised can be considered. We suggest that veterinarians encourage farmers, look for the least cost strategies that they are not using at present and apply these first before moving to the more costly items. ACKNOWLEDGEMENTS We gratefully acknowledge financial support from MDC, SERAD, MAFF, and the Animal Health Trust, and all our colleagues, farmers and veterinarians who have contributed to our knowledge. SAC receives funding from SERAD. REFERENCES Bosberry S. Logue D.N. Laven R. Watson C.L. Ossent P Livesey C (1999) Report of lameness workshop (Harper Adams) "Lameness in the dairy cow" Cattle Practice 7: 307-312 Logue D.N., Berry R. J. Offer J. E. Chaplin S. J. Crawshaw W. M. Leach K. A. Ball P. J. H. & Bax J. (1998) Consequences of "metabolic load" for lameness and disease. International Symposium on Metabolic Stress in dairy cows. 28th and 29th October Edinburgh, BSAS Occasional Publication No 24 83-98. (Abstract in Cattle Practice 7: 113-114) Offer J.E., Berry R.J. & Logue D.N. (1999) The influence of nutrition on lameness in dairy cows. In Recent Advances in Animal NutritionUniversity of Nottingham Feed Manufacturers Conference (33rd 1999 Nottingham) Ed. Garnsworthy P.C. Wiseman J. P59-79 Offer J.E., McNulty D & Logue D.N. (2000) Observations of lameness hoof conformation and lesion formation in dairy cattle over four lactations. Veterinary Record in press Ward W. R. and French N.P. 1997. Foot lameness in dairy cattle. Proceedings of the Association of Veterinary Teachers and Research Workers 25th-27th March 1997 Scarborough. p19 (abst) Appendix 1 attached :Proceedings of the Scottish Lameness Group (SERAD Cco-ordinated Programme including MDC & MAFF projects) Wednesday 8th Sept 1999 University of Aberdeen, Aberdeen AB24 5UA VOL 8 PART 2 Table 3: Strategies for reducing lameness. Strategy Action Relative Cost Reduce infection Immediate treatment of ALL Cases Medium Ensure claw health preventive trim, foot bath low Animal factors season calving/housing training grouping young stock genetics medium medium - high low - high medium - high low-high low but long-term Environment slurry system lying & feeding nutrition high medium - high low - medium

CATTLE PRACTICE The paper described a number of ongoing studies concerning hoof/claw biology and in particular gave the background to the major BBSRC/SERAD project funded jointly with the Hannah Research Institute. The last mentioned involves Professor Knight, Dr Wilde, Dr Hendry and Ms Milne, with a contribution from Dr Logue and colleagues at SAC. The aims of this project include the study during gestation of intervention treatments of dietary methionine and 'photoperiod' (perception of daylength-reduced by use of dietary melatonin and increased by artificial lighting) on (a) indices of lameness and (b) the cellular and molecular biology of claw tissue. The importance of methionine in integumental tissue was described in the context of cysteine synthesis by transulphuration. Cysteine is present in disproportionately lower concentrations of 1-3 residues/100 residues protein in protein supplements or rumen microbial protein. This compares with 6- 10% in cornified claw horn, 6% in intermediate filaments and in excess of 18% in high sulphur intermediate filament - associated protein (IFAPS) fractions. Our studies, and those of others, on the hair follicle have contributed to our understanding of other integumental tissues such as skin and claw. Particular attention has been given to factors influencing cell proliferation and differentiation (including keratinization) in the context of the supply of sulphur amino acids and biotin. For example, methionine is important in the synthesis of BCVA 2000 polyamines, and provides the initial amino acid for peptide synthesis. It is also involved in methylation reactions and may modulate the response to hormonal and other stimuli in mammalian cells. At Aberdeen studies have shown some evidence of increased cysteine deposition, greater hardness and faster rate of growth of claw wall horn when rumenprotected methionine was fed to goats. In addition studies on the expression of intra- (cytoskeletal) and extra-cellular. Adhesion proteins in claw tissue of dairy cattle have demonstrated the presence and location of actin, which frequently co-localised with cytokeratins and desmoglein in the epidermis and vimentin in papillary mesenchyme. (Collaborators in this work, involving an immunohistochemical approach, and partly funded by the Cruickshank Trust, are Amanda Hammond, Tracey Whyte, Mike Birnie and Dr Tim King (Rowett Research Institute)). Funding has also been received from the Universities Federation for Animal Welfare in the form of a studentship for Kirsten Howard. This work also involving Drs Mick Rae and Stewart Rhind of MLURI, is examining the effect of maternal nutrition on dermal and epidermal tissue development in claws of fetal sheep. Reference to changes in cellularity and physical dimensions of basement membrane and dermal and epidermal tissue, with increasing age in samples obtained from cattle in the MDC-funded 'wet/dry' study is mentioned in Paper 3.2. VOL 8 PART 2 APPENDIX 1 Proceedings of the Scottish Lameness Group (Serad Co-Ordinated Programme), September 1999, University of Aberdeen. Paper 1.1. Some Aspects Of Lameness Research In Ruminants Galbraith H., Department of Agriculture, University of Aberdeen, 581 King Street, Aberdeen AB24 5UA. Paper 1.2. Environmental Effects on Cellular and Molecular Biology of Lameness in Dairy Cattle Knight C.H., Hendry K., Wilde C.J., Hannah Research Institute, Ayr, KA6 5HL. Methods have been developed for assessing cell proliferation and function in the bovine hoof. Starting either with a post-mortem hoof or with a biopsy taken from the hoof wall under local anaesthesia, small explants of epidermal tissue are quickly prepared and then cultured for periods of up to a few hours in the presence of radiolabelled amino acids and thymidine. Details of the method have been published (Hendry et al 1995). Using these techniques we have followed cell biological events during the onset and recovery from lameness and have shown that increased cell proliferation followed by an increase in overall keratinization is crucial to a successful outcome (MacCallum et al 1998a). Recently we have shown that cell proliferation and keratinization are both higher in the hind hoof than the fore hoof, supporting an involvement of local physical force as a mediator of the growth response. We have also monitored changes in hoof cell function during pregnancy and lactation (MacCallum et al 1998b). Of particular

CATTLE PRACTICE interest was the variable response to parturition; in summer calving heifers cell activity was high prepartum and decreased post-partum, whereas in winter calvers this was reversed, increasing from low values before calving to higher in early lactation. The precalving differences were shown to be an effect of time of year, since cell activity was high in the summer and low ithe winter irrespective of reproductive state. The post-calving differences reflect a compromise between the lactating cow's desire to turn off non-essential energetic processes so as to partition resources to milk production (the summer scenario) and her need for high hoof cell proliferation to cope with lameness challenge (the winter scenario). The effect of season shows clear parallels with growth of other structures such as hair and antlers and could be mediated by either photoperiod or temperature. It places the winter calving cow at a biological disadvantage when she is also facing the greatest environmental challenge, so BCVA 2000 much would be gained by reversing it so as to create functionally active cells in the hoof during winter. Current work is directed towards this aim, examining the effects of maintaining pregnant heifers at winter solstice daylength from winter to summer (using daily melatonin) and at summer solstice daylength from summer to winter (using artificial lighting). Complementary in vitro studies will look at the role of growth factors, hormones and basement membrane integrity in hoof growth. REFERENCES Hendry K. A. K., Lancelott M. J., Knight C. H., Kempson S. A. & Wilde C. J. (1995). Cell and Tissue Research 281: 93-99. MacCallum A. J., Hendry K. A. K., Robertson S., Wilde C. J. and Knight C. H. 1998a. Cell proliferation and protein synthesis (keratinization) in bovine hoof during the onset and recovery from clinical lameness. Proceedings of the British Society of Animal Science, Scarborough, UK. 1998, p 12. MacCallum A. J., Knight C. H., Wilde C. J. & Hendry K. A. K. 1998b. 10th International Symposium on Lameness in Ruminants, Lucerne, Switzerland. Pp236-238 VOL 8 PART 2 Paper 2.1. Lipids in the Hoof Horn of the Horse and Cow Scaife J., Meyer K., Grant E., Department of Agriculture, University of Aberdeen, 581 King Street, Aberdeen, AB24 5UA. Lipids are important components of hoof cell structures and the intercellular matrix in the cornified epidermis. However, the lipids of hoof tissue and their constituent fatty acids have not been examined in detail. Skin lipids have been well characterised, and although there may be important differences in the lipid composition of skin and hoof lipids, previous work on the former provides an analytical model on which to base a study of hoof lipids. Analysis of equine and bovine hoof lipids was carried out as follows. Hoof tissue to be analysed was reduced to fine shavings using a rasp. Shavings from wall and sole were obtained from nine equine hoof samples and from wall, sole and heel from three bovine hoof samples. Lipid was extracted from these samples at room temperature for successive intervals of 1hr in chloroform-methanol 2:1, 1:1 and 1:2. The total lipid extract was redissolved in chloroformmethanol 1:1 to a concentration of 50 mg/ml. The total lipid from equine hoof samples was separated by TLC using high performance TLC plates. After charring with 50% sulphuric acid, the four main lipid bands were identified by reference to the mobility of standards as polar lipid (PL), non-esterified fatty acids (NEFA), cholesterol sulphate (CS), and neutral lipid (NL). The quantity of lipid in the four main bands was measured by scanning densitometry. The extracts from hoof wall or sole were pooled and separated into the four major bands by preparative TLC. The NL fraction from each pooled sample was further resolved by TLC and quantified as above. Total lipid from bovine hoof samples were separated by two dimensional chromatography using chloroform: methanol: acetic acid: water (90:7:1:0.7 v/v) as solvent system 1 and chloroform: methanol: 25% ammonia (90:12:1.5 v/v) as solvent system 2. The plates were charred with 50% sulphuric acid and the pattern and position of spots compared to that previously published for skin lipids separated using the same solvent system. The fatty acids in the total lipid extracts were methylated by heating at 50°C over night in methanolic HCl. Fatty acids methyl esters (FAME) were applied as a band to 20 x 20 cm silica gel G TLC plates and separated into hydroxy and nonhydroxy FAME by development in hexane:diethyl ether (85:15 v/v). The bands corresponding to hydroxy FAME and non-hydroxy FAME were scrapped from the plates, eluted with diethyl ether and weighed. The non-hydroxy FAME fraction was analysed by capillary column GLC using a 30 M DB225 (0.25 mm ID) column at 240°C. In equine samples a significantly greater (p<0.01) quantity of total lipid was observed in sole compared to wall tissue. Separation of the total lipid extract indicated that there were four main components; a neutral lipid fraction with an Rf value identical to those of pure triacylglycerol (TAG) and cholesterol (C) standards; a band with an Rf value identical to that of CS; a NEFA band with an Rf value identical to

CATTLE PRACTICE that of palmitic acid and a polar fraction with an Rf value identical to phosphatidylcholine (PC). There were no significant differences in the relative proportions of these four components. The NL fraction contained four main bands tentatively identified as (1) hydrocarbons/cholesterol esters; (2) TAG; (3) cholesterol (C) and (4) ceramides (CER) by reference to the Rf values of pure standards. The relative proportions of these four bands were similar in the wall and sole NL fractions. Non-hydroxy FAME profiles were similar in both tissues. The major saturated fatty acids present were C16:0 and C18:0 (wall, 174.1 and 356.6; sole, 161.1 and 302.6 g /kg non-hydroxy FAME respectively). Very long chain fatty acids (VLFA) with equivalent chain lengths (ECL) of 24.76, 26.14, 27.36 and 27.59 were identified in both tissues. Sole also contained fatty acids with ECLs of 31.63 and 32.72. Overall, VLFA accounted for 193.7 and 231.7 g/kg of the total FAME in wall and sole respectively. BCVA 2000 The total lipid content of bovine hoof sole, heel and wall was 23.9, 29.2 and 15.1 g/kg respectively. Separation of bovine total lipid samples by 2D TLC showed the presence of neutral lipids, triacylglycerols, cholesterol, 5 or 6 ceramide bands and polar lipids. There was a high degree of correspondence with the lipid profile previously reported for pig skin epidermis. The FAME content of the total lipid fractions of sole, heel and wall were 560, 410, and 635 g/kg respectively. Of these FAME, non-hydroxy FAME accounted for 120, 150, and 150 g/kg FAME respectively. Non-hydroxy FAME were composed predominantly of C16:0, C18:0, C18:1, C18:2 and C18:3. In sole, heel and wall the total proportion of these fatty acids was 552, 626 and 570 g/kg respectively. The proportions of fatty acids with chain lengths between C18 and C22 was 139, 119 and 83 g/kg respectively and the proportion of VLFA (>C24:0) was 85, 75 and 26 g/kg respectively. VOL 8 PART 2 Paper 3.1. Effects of Wet v Dry Feeding and Housing Type on the Pathogenesis of Claw Horn Disruption in First Lactation Heifers: The Bristol Study Webster A.J.F., Bristol University Veterinary School, Langford, S40 5TD. The first year of this study involved 40 Holstein/Friesian first calving heifers, randomly allocated to four groups, each of ten animals. The groups were:- 1. Straw, dry: housed in a straw yard, fed a dry (61%DM) forage diet based on 0.6 grass silage, 0.3hay plus 0.1 soy meal 2. Straw, wet: housed in a straw yard, fed a wet (25%DM) diet based on 0.6 (wetted) grass silage, 0.35 maize silage plus 0.05 soy meal. 3. Cubicle, dry: housed in a well-designed cubicle shed, and fed the dry diet as above 4. Cubicle, wet: housed in a good cubicle shed and fed the wet diet as above. Dairy cake (20% crude protein) was fed at 0.4kg/l above 15l milk/day and the heifers fed the dry feed produced, on average, 18% less milk than those on the wet diet. There were no effects of feed on body condition and no effects of housing on milk yield or body condition. All feet of all animals were observed, photographed and recorded for lesions to sole and heel according to the method of Leach et al. (1998) at calving -4, +4, +8, +16 and +24 weeks. All the solar lesions were those associated with claw horn disruption (CHD). There were no cases of digital dermatitis. All animals were locomotion scored (1-6) at the time of each series of foot observations and each heifer was video-recorded twice for slow motion gait analysis Sole lesion scores are shown in Table 1. Table 1: Claw lesion scores for cubicle and straw housed “wet” & “dry” fed heifers. Time (+/- calving) Straw dry Straw wet Cubicle dry Cubicle wet Lesion scores (Lesion only arithmetic) C-4 1.2 2.1 2.1 1.8 C+4 6.8 3.3 7.8 12.1 C+8 6.7 4.8 12.7 18.7 C+16 2.7 2.1 10.7 13.6 C+24 1.6 1.7 7.4 5.7 Cumulative scores (Lesion X Area geometric) C-4 3.8 4.7 7.3 3.0 C+4 25.3 14.1 27.4 211.3 C+8 36.1 23.9 87.6 251.4 C+16 9.8 7.4 93.6 283.4 C+24 5.9 6.2 39.3 47.3 In all groups arithmetic lesion scores for CHD increased to a peak at 8 weeks after calving but declined thereafter. Lesion scores were significantly higher in cubicles (P<0.001), moreover, in cubicles only, CHD was significantly worse on the wet than

CATTLE PRACTICE on the dry feed (P<0.05). This difference was accentuated by the cumulative lesion x area scores (p<0.001 for both effect of cubicle housing and wet feeding within cubicles after logIt transformation). Substantial heel erosion was observed in the straw yard, the effect being significantly more severe in the front feet. Little such erosion was recorded in cubicles, but this appeared to be because the depth of the heel was much less in these animals. There were no significant differences between groups in toe growth, wear or angle, nor in sole hardness. Locomotion score was significantly affected by housing type and time in relation to calving in a similar manner to lesion score but the linear correlation between the two scores was very low. The data suggest that a 3-point mobility scale; sound, tolerably lame and intolerably lame would be best in most studies This main project, which has been funded by the Milk Development Council, will be extended into the winter of 1999-2000 to address two further questions namely:- 1. Can the severity of CHD in first-calving heifers be reduced by housing them in straw yards from C-4 to C+8 before introducing them to cubicles? BCVA 2000 2. What are the carry-over effects of CHD from first to second lactation and how are they influenced by housing? In particular is it possible to avoid recurrence of severe CHD by switching cows from cubicles to a straw yard in their second lactation or are such feet 'irreparably' damaged? Finally in a BBSRC funded study feet are being collected from heifers before and during first lactation to study the biomechanics and biochemistry of the suspensory apparatus within the foot. Preliminary studies suggest that the force necessary to separate the pedal bone from the hoof horn may be reduced in the periparturient period. Breaks occur within the collagen minitendons, not at the basement membrane within the laminae. Preliminary biochemical studies suggest a link between this loss of strength and changes in the metalloproteinase enzymes responsible for maintaining the integrity of the connective tissue within the foot. REFERENCE Leach K.A., Logue D.N., Randall J.M. & Kempson S.A. (1998) The Veterinary Journal 155: 215-225. VOL 8 PART 2 Paper 3.2. Effects of Wet v Dry Feeding and Housing Type on the Pathogenesis of Claw Horn Disruption in First Lactation Heifers: The Scottish Study Logue D.N1., Leach K.A1., Offer J.E1., Berry R1., Hendry K2., Galbraith H3., & Kempson S.E4., 1 SAC Ayr KA6 5AE 2 HRI, Ayr KA6 5HL 3 Aberdeen Univ. AB24 5UA 4 R(D)SVS Edinburgh University Preliminary work at SAC suggested that the diet of the young growing first calving heifer might affect the health of the claw in the first lactation (Logue et al 1994). This present experiment and the aligned study at Bristol were therefore designed to examine the effect of diet before calving. Two groups of heifers (29) were allocated to experimental groups at birth (autumn 1997) and fed either a WET diet grass silage with limited concentrates (0 to 1.5kg) or a DRY diet barley straw and concentrate (4 to 7.5kg). The diets were balanced for ME and CP. Initially the diets were also balanced for sugar and starches but alterations to ensure both parity between groups and adequate weight gains to ensure bulling weight targets were met (see Figure 1) meant that this was not possible after Dec. 1998. Figure 1: Growth v target for WET & DRY heifers Fig 1 Growth v target for WET & DRY heifers 200 250 300 350 400 450 500 550 600 650 24/07/98 12/09/98 01/11/98 21/12/98 09/02/99 31/03/99 20/05/99 09/07/99 28/08/99 17/10/99 06/12/99 kg dry wet target Service started Service stopped Wet Dry (kg/d 1= 1.5 2= 1.0 3= 1.0 4= 1.0 7.0+0.5kg 5= 0.5 7.5+1.0kg 6= 0.0 1 2 3 4 5

CATTLE PRACTICE From October 1998 the animals were housed in Dutch Comfort cubicles commensurate with their size. In addition, in the second summer they have remained housed until calving. Once calved all heifers will be put on the same diet (a standard grass silage and concentrate) and the DRY group will be allowed an "interim diet" during the estimated last 4 weeks of pregnancy. Various parameters associated with claw health have been monitored throughout the life span of these animals. In addition 3 from each group were sacrificed at 1 week and 6 months of age, and 1 month after housing in 1998. Three further animals from each group will be sacrificed at approximately 4 weeks post-calving this winter. All feet of all animals were observed, photographed and recorded for lesions to sole and heel according to the method of Leach et al (1998) at 6, 12, 15 & 18 months post-birth. Figure 2 shows the summary lesion scores for all claws. There were significantly more sole and white line lesions in the WET group (p>0.05). Heel erosion was very variable but was significantly worse (p<0.05) in the WET in the last two examinations. Unfortunately both groups were affected by interdigital and digital dermatitis but there was no significant difference between the two groups. While there was no significant difference for growth and wear, the hardness (by Shore A meter) BCVA 2000 was significantly higher in the DRY group for the bulb and the sole. Admittedly numbers are very small but the various histometric parameters of the claws from the sacrificed animals 3 per group (at 2 weeks and 6 months) showed no significant difference between groups but there were differences with age. Similarly, while initially (2 weeks and 6 months) there were no apparent cellular differences between groups, the last group (at 12 months) showed a higher protein and DNA synthesis in the WET heifers. All animals were locomotion scored (Manson & Leaver 1998) fortnightly but this data has still to be fully analysed. A simple behavioural time budget conducted in the summer of 1999 (they were housed all summer in cubicles) showed that the WET heifers lay significantly longer (p<0.05), similarly ruminated for significantly longer and stood in the passageway for significantly longer. A study of the two diets using an in sacco degradability test showed that the DRY diet degraded significantly more slowly. This was associated with significantly less total protein, albumen, phosphorous and glutathione peroxidase in the blood of these cattle taken at the time of foot examinations (time also had a significant effect). In summary the results to date show an advantage to the DRY over the WET group in terms of claw health but it remains to be seen if this is maintained through the calving and first lactation period. ACKNOWLEDGEMENTS Colleagues in SAC and BioSS, and funding from MDC. SAC receives funding from SERAD REFERENCES Logue D.N., Offer J.E., & Kempson S.A. (1994) Proceedings of the VIIIth International Symposium on Disorders of the Ruminant Digit and International Conference on Bovine Lameness, Banff Canada 26th June to 30th June 1994, p274. Leach, K. A., Logue, D. N., Randall, J. M. and Kempson, S. A. (1998) The Veterinary Journal 155: 215-225. Manson F & Leaver D (1988) Animal Production 47: 185-190 VOL 8 PART 2 Figure 2: Sole lesions for WET & DRY 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 10/03/98 18/10/98 19/01/99 18/05/99 date Log (sole lesion score+1) dry wet ** *** Paper 4.1. Dairy Cow Foot Lameness Research at ADAS Bridgets Livesey C.T., VLA Addlestone, KT15 3 NB. The herd at ADAS Bridgets is a commercial dairy unit of Pedigree Holsteins. It does not have a high incidence of lameness. Recorded causes include a moderate incidence of interdigital conditions, in particular granulomas and endemic digital dermatitis, sole ulcers and penetrating wounds and abscessation of the sole and white line. The condition described as sub-clinical laminitis syndrome (SLS) which includes changes in foot conformation and horn quality, especially the presence of haemorrhages and ulcers in the plantar surface of the feet is seen. The changes appear to be most severe in the lateral hind claws. Since sole ulcers occur infrequently and yet other features of SLS are expressed by the herd it must be assumed that an additional risk factor, not currently, or commonly present at ADAS Bridgets is required to cause sole ulceration. Qualitative uncertainty analysis has been utilised to identify possible risk factors for development of SLS that have been tested in controlled studies. In these studies the haemorrhages affect the sole and the solear margin of the white line. The haemorrhages were virtually eliminated by housing animals in straw yards and were much more severe for animals housed on newly laid concrete. The site and speed of resolution of the haemorrhages, amino acid content

CATTLE PRACTICE of the horn and restriction of the lesions to the lateral claws of the hindfeet suggest the haemorrhages were not caused by laminitis. Excessive wear of the lateral hind claws is ubiquitous. This wear is predominantly seen in the lateral wall and results in an extension of the bearing surface over the sole. In severely affected animals the toe length may be decreased to below 7.5cm and a decrease in toe angle as a result of excessive heel wear has also been seen. Medial hind claws are usually not excessively worn. Excess wear is less severe in second lactation than in first lactation and is also moderated by housing in straw yards. This excessive claw wear could predispose the claw to penetrating wounds and abscessation and also to abnormal weight distribution. While a primary cause of the abnormal and excessive wear is likely to be abrasive underfoot conditions, other possible predisposing factors include horn quality (different in first and second lactation cows) and gait. The dishing hind limb gait seen commonly in Holstein cows may cause excessive abrasion of the lateral wall of the lateral hind claws. The gait abnormality may be further exacerbated by gait changes caused by the presence of a large udder and the need to maintain grip on a slippery surface. The apparently greater resilience to wear of the lateral hind claws of second lactation cows suggests a significant alteration in horn quality may have occurred. Other evidence of changing horn BCVA 2000 quality includes changes in the proportions of cystine and methionine in the hoof horn during the last month of first pregnancy or early in first lactation. These sulphur containing amino acids are known to be limiting substrates in keratin synthesis and changes in the proportions of these amino acids in hoof horn suggest that the proportions of fibrillary and interfibrillary proteins have changed. Heel erosions/slurry heel appears to be comprised of/contributed to by two distinct conditions:- • pitting of the horn surface; presumably caused by keratolytic substances in the environment but possibly predisposed to by poor horn quality; • exposure of the corium and separation of the horn from the underlying corium which appears to be an abnormality of horn formation. Although this condition does not cause lameness it must affect the biomechanics of locomotion and weight distribution and may predispose to secondary infections of the keratin and soft tissues underlying the damaged keratin. Heel erosion may also predispose to digital dermatitis infection. As a result of these findings the approach in current studies is to attempt to induce horn quality changes during first pregnancy which produce horn of equivalent resilience to that not previously seen until second lactation. VOL 8 PART 2 Paper 4.2. Digital Dermatitis in an Endemically Infected Herd? Laven R., ADAS Bridgets, Martyrs Worthy, Winchester, Hants. Several studies at ADAS Bridgets have been investigating the epidemiology of digital dermatitis in a herd endemically infected with digital dermatitis (DD). The first study was designed to identify the housing and other management factors that could increase the spread of DD in an endemically infected herd. In particular it was designed to compare the effect of bedding and scraper type on severity, duration and recurrence of DD lesions. The cows were housed in three buildings: straw yards, cubicles with tractor scraping and cubicles with automatic scraping. There was a significant effect of housing group on the incidence of DD, with the cows housed on straw yards having the lowest incidence, and those housed on automatically scraped cubicles having the highest. The severity of the lesions was lowest in the straw yard, but there were no differences between the severity of lesions found in the two cubicle groups. This study suggests that cows that develop DD do not subsequently develop a protective immune response. Cows developing DD on one hind foot were more likely to have it on the other foot, and previous digital dermatitis infection increased the risk of subsequent disease. However, immunity may play a role in the epidemiology of DD. At ADAS Bridgets approximately 50% of heifers have or have had DD by the time of calving. This increases to around 70% within 12 weeks of calving, but very few heifers develop digital dermatitis for the first time during the rest of their first lactation. The same pattern of infection has now been seen in two different years. In studies of cows over a twenty week period, even in the worst affected group around 20% of cows never developed visible lesions of DD. This suggests that there may be a significant population of cows that are inherently resistant to DD. Further research is needed.

CATTLE PRACTICE The laminar region has attracted much interest as laminitis or inflammation of the laminae has been implicated in the aetiology of claw horn lesions of cattle. Claw horn lesions are present in 70% of lame dairy cows with all the problems consequent to the pain of lameness, loss of milk yield and fertility. Lameness is a major welfare, clinical and economic problem in the dairy industry throughout the world. The definition of laminitis refers to an inflammation of the laminae within the claw. However, the term laminitis is widely and loosely used to describe various lesions of the claw horn even in regions anatomically remote and different from the laminar region (Kempson 1998). Before the aetiology and pathogenesis of claw horn lesions and laminitis can be fully understood, a detailed knowledge of the normal structure is essential. However, most of the veterinary textbooks on anatomy and histology pay scant attention to this region. Many workers in the field of bovine lameness have no, or only a limited knowledge of the structure of the normal laminar region due to lack of a clear reference text. The purpose of this study was to address this deficiency. Four feet from different cattle were collected immediately after slaughter. Serial blocks of tissues about 1cm3 were taken in a proximodistal direction at 0.5cm intervals from the dorsal aspect of the claw starting from the periople to the toe. The blocks were taken from both intact claws (with claw capsule) and exungulated claws (claw capsule removed). Exungulation was done by immersion of claws in a water bath at 65°C for 55 minutes and then making an incision around the coronet and removal of the claw with the help of a vice. The horn, epidermis and dermis were included and studied. Each of the blocks was divided into two, one was prepared for light microscopy and the other for scanning electron microscopy (SEM). Samples for light microscopy were fixed in 10% buffered formalin, and placed in a modified Gooding and Steward's decalcifying solution for one week. Sections about 10μm thick were made and stained with Ledrun's phloxine tartrazine for light microscopy. The SEM samples were fixed in 3% glutaraldehyde, dehydrated in graded acetone, critical point dried, mounted in BCVA 2000 aluminium stubs and sputter coated with gold palladium and observed in a Philips SEM 500. The epidermis of the laminae consisted of a single layer of columnar cells (the stratum germinativum), a layer of maturing cells and the stratum corneum forming laminar horn leaflets. The laminar epidermis leaflets differed from proximal to distal, being short without horn leaflets at the coronary junction, longer in the middle region accompanied by horn leaflets. Distally, the epidermis outer extremity was thicker and gave rise to cap horn. The cap horn formed at the outer extremity formed the interdigitating horn of the white line. The dermal and epidermal laminae formed parallel interdigitating leaflets with a tight dermalepidermal junction. On exungulation at the coronary junction the dermis revealed organised collagen fibre bundles fusing to form a scaffold of dermal laminae. The dermal laminae are enlarged and consolidated by bundles of collagen fibres orientated in a horizontal plane radiating from the dorsal aspect of the distal phalanx. In the distal aspect smaller bundles separate again to fuse with one another to form a framework of the solear papillae. This showed a continuous inter-related network of collagen bundles from the coronary region to the sole. The dermal laminae differed in height from proximal to distal, tapering at the distal end to form papillae that blended with those of the sole. In conclusion, the laminar region is a region of complexity that shows variation in structure from proximal to distal. A detailed knowledge of the structure and physiology of the region is required in order to understand the pathophysiology of laminitis and associated conditions of the claw horn. ACKNOWLEDGEMENTS The authors wish to express their gratitude for support of the Association of Commonwealth Universities who provided a Commonwealth Fellowship. REFERENCE Kempson S.A. (1998) 10th International Symposium on Lameness in Ruminants, Lucerne, Switzerland. pp153-154 VOL 8 PART 2 Paper 5.1. The Structure of the Laminar Region of the Bovine Claw Mgasa M. N. & Kempson S. A. Department of Preclinical Veterinary Sciences, Royal (Dick) School of Vet. Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH.

CATTLE PRACTICE Feet were obtained from a pedigree Limousin heifer, which was slaughtered at 15 months old due to lameness caused by laminitis. She first presented with the condition in the summer of 1998 when she was approximately six months old. At the time of slaughter she could only stand on the toes of her forefeet. The forelimbs were positioned well underneath her body. After slaughter the feet were first photographed and then the left forefoot and left hind foot were prepared for x-ray examination. The medial and lateral claws were separated and a piece of fine wire was attached to the dorsal wall at the toe, with sellotape. The wire extended from the hair horn junction to the tip of the toe. Following x-ray examination one claw of each foot was frozen and sectioned in a sagittal plane. The other claws were boiled out for closer examination of the bones. In addition, blocks of tissue were taken for routine histology from the medial claw of the forefoot and the lateral claw of the hind foot. The remaining claws were exungulated and examined. Blocks of tissue were taken for scanning electron microscopy. Examination of the x-rays, the bones and the sagittal sections showed severe changes in the distal BCVA 2000 phalanges of the claws of the forefeet. The distal phalanges of the hind claws were smaller than expected and the attachment areas of the laminar and sole coria were smoother than normal. The distal phalanges of the front claws showed severe inflammatory changes, bone loss, exostoses, particularly on the dorsal aspect. The distance between the hair-horn junction and the extensor process of the distal phalanx was three times greater than normal. The dorsal wall at the toe was attached to the bone at two points only in the front claws. These observations indicated that the bones had "sunk" within the claw capsule. The gross and histological observations showed the soles and heels of all claws were normal, but overgrown. In the hind claws the histological sections showed slightly enlarged laminae but otherwise normal. As expected the front claws were abnormal. Recognisable, but highly distorted, laminae were confined to the distal region of the toe. The white line was seven to eight times wider than normal and the structure was highly distorted. There were major changes in the distal phalanx and the corium. Possible significance of the observations was discussed. VOL 8 PART 2 Paper 5.2. A Case History - True Bovine Laminitis Kempson S.A. and Mgasa M.N., Department of Preclinical Veterinary Sciences, Royal (Dick) School of Vet. Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH. Paper 6.1. The Use of Modern Statistical Models to Analysis of Lameness and Locomotion from Longitudinal Field Data Hirst W.M. N.P. French University of Liverpool, Leahurst, L64 7TE. The aim of this study is to examine the relationship between cow and farm herd variables and the development of lameness in dairy cattle. By applying modern statistical techniques to formulate multivariate models to describe cases of lameness, a greater understanding of the aetiology of lameness is possible. The Liverpool lameness database was collected for a MAFF project between 1989 and 1992. The database consists of 37 farms in the Wirral, Cheshire, Somerset and Wales. Outcome variables include clinical lameness and locomotion scores, with explanatory variables at the cow level including calving information. A number of farm level variables are also available. There is information on over 12,000 episodes of lameness or foot trimming for about 3,500 cows, and in the region of 60,000 locomotion scores for about 7,000 cows. Lactation information is available for 5,231-cow lactations for 2,200 cows. Two analyses are presented. The first analysis examines the relationship of time to lameness in the second and third lactation by calving season, age at first calving and lactation one lameness history. Time to lameness in lactation one by calving season and age is also considered. In each analysis allowance for extra-variation at the herd and sire level is incorporated via random effects. The Cox model (where no shape of hazard is assumed) and the Weibull model (where the hazard is parameterised) are considered. The second analysis models locomotion scores by lactation number, time from calving, time in the study and time of year. Univariate examination of time from calving, time of year and time in study show the relationship with locomotion scores is complex and cannot be assumed to be linear. Hence a Generalised Additive Model (GAM) approach is adopted where the effect of explanatory variables need not be linear. When considering time to lameness in lactation one season of calving may affect the risk of lameness but this risk is not significant after allowing for extra

CATTLE PRACTICE variation due to herd and sire. For lactation two there is no evidence of a seasonal effect but even after allowing for extra variation there is a strong increase in risk if a cow was lame in the first lactation. For instance the risk of lameness in lactation two for previously lame cows is double that for cows not lame in the first lactation. The trend continues into lactation three but the lack of data restricts the significance of results. The GAM analysis demonstrated that locomotion scores increase with each lactation and the relationship between lactation number and locomotion score is linear. The relationship of time from calving is quadratic - the peak effect is around 4 months after calving. This result is in line with SAC work on lesion scores and calving. Locomotion scores increased throughout the study with a slight decline at the end of the study BCVA 2000 period. The models also demonstrate the relationship between time of year and locomotion scores is difficult to ascertain but there is evidence of a dip in scores for the summer months. The range in probability of lameness for individual cow profiles is between 0.03 and 0.63. A modern multivariate model based approach to the analysis of field records from the Liverpool database can allow us new insights into the aetiology of lameness and quantify relationships between risk factors and cattle lameness. ACKNOWLEDGEMENTS This study is in collaboration with SAC and we gratefully acknowledge funding by MAFF, SERAD, and MDC. VOL 8 PART 2 Paper 6.2. Statistical Analysis of Claw Horn Disruption Le Fevre A., SAC/BioSS/Univ Strathclyde. The epidemiology and aetiology of pododermatitis aseptica diffusa in dairy cattle often referred to as "subclinical laminitis" (SLS) and more recently "claw horn disruption" (CHD) is not yet fully understood yet it is widely considered to be the basis of most claw horn lesions leading to lameness. Using historical databases of observational studies conducted at the Crichton Royal farm, Dumfries it is hoped to achieve a better understanding of this phenomenon. The studies followed four groups of first calving heifers from between one year to three years. All four groups of cows were split into two management systems, low input versus high output. Three of the groups contained both autumn calving cows that calved between September and December and spring calving cows that calved between January and April. Therefore comparisons could be made between the two management systems, the two seasons of calving and, for three of the groups, between lactation's one and two. Preliminary investigation using only one of the four groups focused on the presence versus absence of sole and white line lesions and using a summary statistic for lesion severity and extent for the cow, changes in their severity throughout the first two lactations. The probability of observing a white line lesion at any stage of both lactations for both herds and seasons of calving was approximately 0.9. The probability of observing a sole lesion was different between the two management systems, the first two lactations, and the two seasons of calving, the lowest probability was found among spring calving cows in lactation two in the low input herd. Peak lesion severity was modelled using a quadratic by quadratic curve. Peaks were found to occur between two and four months after calving. In a comparison between the two management systems, the high output herd sustained a higher peak severity, while comparison of the two seasons of calving showed autumn calving cows to sustain a higher peak. Investigation into the hierarchical structure of the data is of further interest. Lesions have been observed to form differently between different claws and sites within the claws. Investigation into the types and extent of differences between claws and sites will also help in the assessment of the three major hypotheses of CHD aetiology. For example, generally one would expect there to be no difference between the left and right side of the cow. This association can be tested using the Spearman rank correlation coefficient, which does not assume normality of data. However, for ordinal categorical data a specific non-parametric measure of association called the G statistic is more appropriate. The G statistic may be interpreted similar to correlation coefficients, such that it will take values between -1 and 1 and the closer it lies to zero the less associated we can say the two variables are. The test for association between left and right outer hind claws proved highly significant. Further work on these associations and hierarchical structure is being undertaken. ACKNOWLEDGEMENTS We gratefully acknowledge colleagues in Liverpool University who are jointly funded and SAC, BioSS, the Univ. of Strathclyde STAMS, generous funding from SERAD, MAFF & MDC. SAC receives funding from SERAD.

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 reduce the development of new clinical cases of digital dermatitis. NON-ANTIBIOTIC PRODUCTS Non-antibiotic treatments are widely used, primarily because non-antibiotic treatments are generally significantly cheaper. Effective non-antibiotic treatments could have a significant role in the control of digital dermatitis, because they can easily be used repeatedly (due to their low cost and because they can be placed in parlour), but there have been few reports of properly controlled clinical trials. Hernandez et al. (1999) reported that a triplex compound of soluble copper, peroxide compound, and a cationic agent was as effective as oxytetracycline in controlling digital dermatitis, but this was a limited trial with only 12 cows per treatment group and needs repeating. Blowey (2000) suggested that daily foot-bathing with formalin for 14 days (after thorough treatment with antibiotics), repeated every 4 to 6 weeks could control digital dermatitis. At ADAS Bridgets, we found that weekly formalin foot-baths in pregnant heifers, kept in an environment where over 50% of cows had had digital dermatitis in previous years, significantly reduced the incidence of digital dermatitis. Further research into the use of formalin in the control of digital dermatitis is required, but it must be stated that formalin should not be used as a treatment for digital dermatitis because of the significant pain it causes when applied to raw lesions. IMMUNITY Control of digital dermatitis could be achieved by stimulation of the immune system if the immune response is protective. However, several studies at ADAS Bridgets, funded by the MDC, suggest that this immunity is not protective. Firstly, as part of a study which examined the hind feet of 350 cows over a twelve week period, the effect of digital dermatitis on one hind foot on the prevalence of digital dermatitis on the other foot was examined. Fifty-two percent of lesions were found on the right hind and 48% on the left. Assuming that there was no relationship between digital dermatitis on one foot and digital dermatitis on the other, the percentage of cows with lesions who had lesions on both hind feet should have been 50%. However, 68% of cows with lesions had lesions on both feet (see Figure 1). This suggests that the presence of digital dermatitis on one foot is associated with an increase in the risk of digital dermatitis on the other (odds Control of Digital Dermatitis Laven R., Adas Bridgets, Martyr Worthy, Winchester, Hants. SO21 1AP. INTRODUCTION Digital dermatitis is a skin condition of cattle which usually affects the skin on the bulbs of the heel or between the digits. The condition causes inflammation and skin damage and as it progresses the lesion becomes more erosive and the affected area expands. The lesion causes considerable pain to the cow, resulting in reduced mobility and feeding, with consequent loss of milk production. Of particular concern in terms of cow welfare is the fact that the condition can persist for months if it is untreated (Peterse 1992). Digital dermatitis is probably one of the most common conditions causing lameness in housed dairy cattle. A recent report suggested that it accounted for 25% of all lameness in recorded herds (Watson 1999), and Dawson (1998) in a survey of 258 herds across the UK found that over 70% of herds were affected. Indeed it is probable that digital dermatitis is the main disease responsible for the failure of current management regimes to reduce the overall incidence of lameness (Blowey pers. comm). Thus, the development of strategies that can control or, better still, eliminate the spread of digital dermatitis is urgently required. ANTIBIOTIC FOOT-BATHS Antibiotic foot-baths are an effective treatment for digital dermatitis. Laven and Proven (2000) showed that four days after foot-bathing with erythromycin (at a concentration of 210g/100l of water), cows with digital dermatitis had a significantly reduced level of lameness and associated pain, and that the antibiotic treatment had stimulated the healing of the digital dermatitis lesions. However, eleven days after treatment, although the lesions were still significantly better than they had been before treatment, the lesions were not significantly better than they were four days after treatment. Thus for continued improvement and control of digital dermatitis, repeated antibiotic foot-baths are necessary. The interval between foot-baths is dependent upon the prevalence and the severity of the disease, but between one and two weeks is probably best initially, with a reduction in frequency as the prevalence and severity reduces. Such a regime will control digital dermatitis but not eliminate it. However, repeated antibiotic foot-bathing is expensive, which results in most farms using antibiotic foot-baths for treatment rather than control, or using individual topical antibiotic treatment. Individual treatment is effective, but, because not all animals are treated, it does not

CATTLE PRACTICE ratio 1.4:1). This suggests that any immune response is either not protective, or not good enough to overcome the environmental challenge. BCVA 2000 The aetiology of digital dermatitis is complex. Invasion by treponemes is probably the primary cause of digital dermatitis, however several morphologically distinct species of treponeme have been isolated from digital dermatitis lesions. Nevertheless, one treponeme may be the primary organism and an immune response to this organism could be protective. Demirkan et al. 1999 isolated a treponeme from digital dermatitis and produced an ELISA for antibodies to this spirochaete. This ELISA was used in an investigation of the development of digital dermatitis. thirty heifers were examined for digital dermatitis from three months of age until calving with samples taken for serology every three months. Significantly more animals with digital dermatitis were found to have a positive antibody response, at the time of the examination, than animals without digital dermatitis, however the proportion of animals with digital dermatitis and a positive antibody response was very low (<20%). When the response of individual cows rather than lesions was analysed, this proportion increased to 28%, which although not significant suggests that a positive antibody response developed after the lesion. Therefore the antibody response does not appear to be protective, which is further confirmed by the fact that only one cow which did not have clinical digital dermatitis had a positive antibody response at any time. These data suggest that the immune response is not protective and that the prevention of digital dermatitis by early exposure or the development of a vaccine are not suitable for the control of digital dermatitis. ENVIRONMENTAL CONTROL Environmental factors play a major role in the development and progress of digital dermatitis (Laven 1999). More research is required into the environmental control of digital dermatitis, but the most important factor for reducing the spread of digital dermatitis is controlling slurry. Housing cattle in straw yards significantly reduces the incidence and severity of digital dermatitis, and tractor scraping significantly reduces the incidence of digital dermatitis when compared to automatic scrapers, probably because it removes slurry without the buildup associated with automatic scrapers. Other areas where slurry can build up include collecting yards, feeding areas and areas around water troughs. In common with other causes of lameness, housing design is paramount in the control of digital dermatitis. Poorly designed cubicles increase the amount of standing time which increases the contact time with slurry. Better cubicles mean less digital dermatitis. VOL 8 PART 2 Figure 1. Effect of dermatitis on one foot on the prevalence in the other foot 0 10 20 30 40 50 60 70 Left Foot Right Foot Both Feet (expected) Both feet (actual) Percentage of lesions Another study investigated the impact of exposure to digital dermatitis prior to calving on the prevalence after calving. The animals were allocated, 3 months before calving, to one of three treatments: Fresh straw, old straw used by animals with digital dermatitis and cubicles used by animals with digital dermatitis. They were randomly allocated based on their antibody to Borrelia burgdorferi , which resulted in the three groups having a significantly different prevalence of digital dermatitis at the start of the study. However, there was no significant change in prevalence of digital dermatitis between allocation and calving, although there was a trend for a fall in the prevalence of digital dermatitis in animals on clean straw (P=0.06). After calving all three groups were housed in the same cubicle yard, however there was no significant increase in digital dermatitis in any of the groups, which meant that the prevalence of digital dermatitis in each group was not significantly different from what it had been 3 months before calving. This is shown in Figure 2. This suggests that exposure of pregnant heifers to digital dermatitis before calving has no significant impact on the prevalence of digital dermatitis after calving. Thus, there is no protective effect associated with exposure to digital dermatitis. Figure 2. Effect of housing pre-calving on prevalence of digital dermatitis 0 10 20 30 40 50 60 70 80 3 months before Calving 3 months after Prevalence Old straw New straw Cubicles

CATTLE PRACTICE CONCLUSIONS Long-term control of digital dermatitis is best achieved by improving the environment. This will also have a significant impact on other forms of lameness. However, any environmental improvement must be maintained as the reductions in digital dermatitis achieved will rapidly disappear. ACKNOWLEDGEMENTS This article is based on research funded by the MDC in collaboration with the Wood Veterinary Group and The University of Liverpool BCVA 2000 REFERENCES Blowey R., (2000) Control of digital dermatitis Veterinary Record 14: 295 Dawson J.C., (1998) Digital dermatitis-survey and debate Proceedings of the XX World Buiatric congress, Sydney p91 Hernandez J., Shearer J.K., Elliott J.B., Comparison of topical application of oxytetracycline and four nonantibiotic solutions for treatment of papillomatous digital dermatitis in dairy cows. J Am Vet Med Assoc 214: 688-90 Laven R., (1999) The environment and digital dermatitis Cattle Practice 7: 349-354 Laven and Proven (2000) The use of antibiotic foot-baths in the treatment of bovine digital dermatitis Veterinary Record in press Peterse D.J., (1992) Foot Lameness in Bovine Medicine Ed. Andrews A.H. Pub Blackwell, Oxford p353-364 Watson C. (1999) Lameness in cattle - lesions and diseases of the skin - part 1. UK Vet 4: 51-60 VOL 8 PART 2

CATTLE PRACTICE BCVA 2000 VOL 8 PART 2

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 This was a discussion based seminar which addressed the following issues:- Treatment needs to be seen in perspective • Needed when prevention fails • None are 100% ''No Quick Fix, No Miracle Cures'' Options for intramammary infections (IMIs) • Cull ! • Leave - ? self cure • Therapy - traditional (some science) - alternative (little science) Goals of treatment • Bacteriological cure • Clinical cure (minimise pain) • Cell count down (limited damage) • No pharmaceutical milk failures (NB new test: Delvo SP with increased sensitivity) Do we need antibiotics?? For treatment: Yes!! because…….. • Improves bacteriological cures in most cases • reduces chronic infection (economics and welfare) • SCC benefits • Nothing shown (scientifically) to be superior Resistance - no evidence lactating therapy important BUT………... Even using antibiotics • Bacti cures - 40-100% • Clinical cures - 75-100% • SCC down - 40-100% Success depends on… • The bacteria • Time since infection occurred BUT… • we cannot know what bacteria is involved as we treat (yet) • by the time we find out, it's too late!!?? To overcome this, we need to …. • Know our herds • Know their likely pathogen (s) • Find it early UNDERSTANDING OUR HERDS High BMSCC commonly • Staphs • Strep dys, uberis • (Klebsiella, Seratia) Low BMSCC commonly • E coli • Strep uberis NB. Bulk SCC not correlated to mastitis incidence but is to type. Why Know Your Herds' Pathogens ? • Target type of treatment to major causes of mastitis on that farm HOW TO KNOW YOUR HERDS' PATHOGENS Χ Bulk milk sampling? Χ High SCC cows Χ A few at odd times 4 All cases pre-treatment then freeze; grow all or a representative sample each year HAVE A HERD STRATEGY If Staphs • poor cure from treatments - REVISE CONTROL • try beta-lactamase resistant antibiotics or penicillin Streps • Variation in cures • Penicillin Treating Bovine Mastitis Green M.J., Orchard Veterinary Group, Wirrall Park, Glastonbury, Somerset BA6 9XE. ABSTRACT Vets have a responsibility to cows (welfare), clients (economics) and consumers (food quality) to have a calculated approach to the treatment of mastitis. A farm based approach involving diagnosis and appropriate targeted therapy is described and recommended for best results. Client education in some areas will be necessary.

CATTLE PRACTICE Coliforms • Stripping +/- oxytocin (?G-ve antibiotics) • More likely to have systemic signs: NSAIDs • Have a policy for severe cases (see later) WHAT IF SUCCESS RATES ARE POOR! Early detection • NB average herd has to detect just one mastitic quarter in over 7000 normal quarters milked Detection • Variation massive - most farmers over-estimate! • Strip • Look • Feel • Examine filters • Conductivity • If in doubt….Californian milk test 1ST CHANCE IS BEST - EARLY - LONG?? Prolonging all courses (5-7 days)- for Staph and Step uberis herds? • Better cure rates • Less subsequent spread • Good for cell counts • BUT • More milk out • Higher TX cost If only 1 case every 2 weeks per 100 cows shouldn't we HIT IT HARD? (and use a 7 day milk withdrawal). Possibly more science needed here. FUTURE • Early (reliable) detection • Fast pathogen identification • Improved information on better bacteriological cures Coliforms: The more severe case • Stripping (oxytocin) • NSAIDs • Antibiotics - systemic • Fluids - hypertonic (x2-3) • Ca Have a farm policy for severe cases especially on low BMSCC farms BCVA 2000 ''It won't clear up'' - an approach • Is the cow worth a try? • Culture frozen sample(s) or take sample asap and suggest freezing in future • If Staph - consider culling • If unknown; likely to be G+ve • Use a prolonged course (7 days) or pulse ? Penicillin ? Systemic antibiotic ? Check for bacteriological cure post treatment Shooting in the dark, belatedly with 3 tube course =Hopeless!! Have we got our focus right??? Is it on the stubborn case Should it be on farm level In the current climate of... • Farm assurance • Health schemes • Public/retail scrutiny We are duty bound to take a sensible pro-active approach to the treatment of common conditions When to be careful……….. Treating 'normal' (SCC<200) with antibiotics Around calving Herd blitz Low SCC herds (eg. cows over 100,000) ? Removes minor pathogens ? Unnecessary use of antibiotics Can be catastrophic! FARM BASED APPROACH 1) What pathogens predominate? 2) Early detection 3) Appropriate treatments (antibiotics and others) 4) Record and monitor 5) Review (NB 7 days for all cases) 6) Change as necessary - return to point 1 VOL 8 PART 2

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 INTRODUCTION The objective of any milking machine, irrespective of manufacturer or configuration must be to milk cows safely, gently, quickly and efficiently. When theses operating parameters are optimised, adverse effects of the milking machine on new infection levels should be minimal. The milking machine can affect levels of new infection in two main ways:- (i) Acting as a vector by transporting bacteria towards an udder quarter. (ii) By affecting the condition of the teat and impairing the cows natural defence. The milking machine as a vector of mastitis pathogens It is well documented that liner slip is linked with increased rate of new mastitis infections (1). The sudden admission of air at atmospheric pressure can cause milk to impact on the teat orifice, increasing the opportunity for pathogens to be forced into the teat canal (2, 3). Liner slip is influenced by a number of factors including:- (i) Design of liner and particularly liner mouth piece. (ii) Age of liner. (iii) Cluster support and position. (iv) Vacuum level. (v) Effective vacuum reserve. Most commercially available liners have a life expectancy of around 2500 cow milkings. After this time, a combination of regular movement and exposure to cleaning agents containing halogens will cause the material to loose tension. It will then be more prone to slippage. To improve liner performance and reduce slippage it is essential the cluster hangs vertically in all planes with the cluster weight distributed evenly on each quarter. This is often achieved using long milk tube supports or cluster support arms. Increasing working vacuum level within the milking machine will result in a higher vacuum level in the liner mouthpiece. This can reduce the amount of slippage noted but will often result in increased levels of localised oedema around the base of the teat manifested as a palpable ring. Inadequate effective vacuum reserve will lead to vacuum fluctuations when clusters are applied, removed or there are uncontrolled admissions of air. As well as increasing the opportunity for reverse movements of milk, inadequate effective reserve can dramatically increase cases of liner slip noted. When liners become flooded with milk it seems likely that milk will collect bacteria from the teat surface or other quarters and increase the bacterial challenge at the teat end. As herd yields increase, there is a corresponding increase in quarter milk flow rates (4). Liners traditionally were manufactured with a short milk tube 7-8 mm internal diameter. Vacuum recordings taken in the short milk tube of these liners during high peak milk flows often show wide cyclic fluctuations which are indicative of flooding. Increasing the bore of the short milk tube to 10 mm reduces the amplitude of the cyclic fluctuation and reduces the opportunity for milk to move back towards the teat orifice (5). Ensuring cow housing is well managed and teats are thoroughly prepared before attaching the cluster will further reduce the opportunity for pathogens to be spread during milking. Inadequately sanitised milking equipment can act as a reservoir for pathogens. This can be a particular problem where a group of mastitic cows is milked at the end of a milking session and fresh calvers at the start of the next session. Comprehensive sanitisation relies on a combination of adequate volumes of hot water, correct concentration of detergent/steriliser and high flow rates. Teat condition The milking machine can be responsible for a number of well documented teat conditions (6). The most commonly reported 'damage' is keratinisation of the teat canal. Mild hyperkeratosis alone should not be considered a problem (7). There is evidence that the rate of clinical mastitis is higher in cows with moderate to severe hyperkeratosis and that hyperkeratosis is linked closely to milk yield (8). Cows which produced less than 5500 kg in a 305 day lactation had much higher proportion of normal teat ends (30%) than higher yielding animals. When 305 day yields were above 8200 kg the percentage of normal teat ends fell to less than 9%. Hyperkeratosis is a multi-factorial condition. The presence of hyperkeratosis is linked to milk yield, quarter milk flow rate, unit on time, liner compressive load and teat shape. Machine Milking and Mastitis Ohnstad I., ADAS Bridgets, Martyr Worthy, Winchester, Hants, SO21 1AP.

CATTLE PRACTICE Cylindrical or pointed teats tend to display a higher degree of hyperkeratosis than teats with a flat or inverted end (9). There may also be variation in the type of teat duct keratin between cows. The method in which the liner applies pressure to the teat end during the liner closure phase of the pulsation cycle is important in maintaining blood circulation and allowing the restoration of keratin. The vertical component of this force is critical (10). If the compressive load applied by the liner on the teat end is reduced, as a result of worn liners or incompatible liner / shell and pulsation system, the rate of keratin removal will be increased. Evidence published to date could suggest that an increased degree of hyperkeratosis with the link to new infection is something which has to be accepted as genetics and management combine to produce higher yielding cows. However, recent work from Denmark is suggesting that it is possible to milk high yielding cows without a consequent deterioration in teat condition (11). Unit on time was reduced with no yield penalty when the flow rate settings to determine end of milking were adjusted from a threshold of 0.2kg/min to 0.4kg/min. Teat condition improved markedly and the levels of clinical mastitis were reduced. In many herds in the USA where milking is carried out three times daily, the end of flow threshold has been adjusted as high as 0.7 kg/min. The study stressed the importance of a thorough pre-milking routine to ensure the cows were adequately stimulated before unit attachment. It is suggested that between 10 and 20 seconds of teat cleaning is required to produce satisfactory milk let down. To maximise the effect of the let down the units should be attached between 60 and 90 seconds after the cow is first touched. Other forms of reported teat damage include congestion, oedema and colour change (12). Oedema of the teat can be measured and may be related to the action of the milking machine (13). During mastitis investigations, limiting examination of the milking machine to a static (dry) test between milkings could result in an underestimation of the influence of the BCVA 2000 milking machine. Examinations during milking allow exploration of the interaction between the milking machine, the cow and the operator. The thoroughness of teat preparation, accurate adjustment of ACRs or timely removal of units, cluster position and positioning of the animal relative to the stallwork and milking unit are all important factors. A number of systems have been developed to allow critical evaluation of the complex interaction between the milking machine, the operator and the cow (12, 14). CONCLUSION The milking machine is able to influence mastitis in a number of ways. Ensuring the milking machine is operating as designed and is milking cows which are well prepared and stimulated will reduce the opportunity for the machine to spread pathogens. Closely monitoring condition of teats on a routine basis will ensure physical damage to sensitive tissue is avoided and problems can be rectified before there is an opportunity for the damage to result in elevated levels of new infection. REFERENCES 1. O'Shea J (1987) Section 2, IDF Bulletin No. 215, International Dairy Federation, Brussells, Belgium. 2. Thiel C, Cousins C, Westgarth D & Neave F, (1973) J Dairy Research 40: 117-129. 3. Cousins C, Thiel C, Westgarth D & Higgs, (1973) J Dairy Research 40: 289-292 4. Mein G (1998) Proceedings of the British Mastitis Conference, Stoneleigh, UK. 5. Grindall R & Hillerton J (1991) J Dairy Research 58: 263 - 268. 6. Baines J (1993), Cattle Practise July 1993, 1 part III, 191 - 196. 7. Shearn M & Hillerton J (1996) J Dairy Research 63: 525 -532. 8. Sieber R (1979), M Sci thesis, University of Minnesota, USA 9. Hamann, IDF Bulletin 215: 1982 10. Mein G, (1986), J Dairy Research, 53: 17. 11. Rasmussen M (1993), J Dairy Research 60: 287 - 297. 12. Hillerton J, Ohnstad I & Baines J (1998) Proc. of National Mastitis Council, 37th Annual Meeting, p 75 13. Hamann J & Mein G (1993), J. Dairy Sci. 76: 1040 14. Farnsworth R (1996) Proc. National Mastitis Council, 35th Annual Meeting, p 93. VOL 8 PART 2

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 Hereford x Friesian once found in around 75% of all recorded lowland and upland suckler herds (MLC, 1987). However, the increase in the proportion of Holstein genes in dairy cows during the 1980s (from approximately 8% in 1979 to 62% in 1988; MLC, personal communication) forced many dairy producers to the use continental-beef semen on their cows, in an attempt to overcome the poor carcass quality and low value of the traditional Beef x Holstein calf (MLC, 1985 and 1995). This resulted in an increase in the number of continental x dairy heifers entering the beef herd during the 1990s (MLC, 1992). As young cows, such animals have increased metabolic requirements due to their increased potentials for mature size and milk yield (Tables 1 and 2a), making them less suited for herds in less favoured areas where food supplies are limited. Suckler Cow Nutrition: I. Management by Condition Score Sinclair K. D1., Suttle N. F2. 1Department of Applied Physiology, Scottish Agricultural College, Craibstone Estate, Bucksburn, Aberdeen, AB21 9YA. 2Moredun Research Institute, Pentlands Science Park, Bush Loan, Midlothian, EH26 0PZ. INTRODUCTION The formulation of feeding strategies for beef cows must take account of the variation that exists between genotypes in the attainment of mature size and milk yield potential, as these are the principal determinants of the cows nutrient requirements. Geographical location and husbandry system, on the other hand, will determine the level and pattern of nutrient supply. The challenge for the suckled calf producer is to match nutrient supply to the requirements of the cow while recognising her tremendous ability to store excess nutrients (principally energy in the form of fat) in times of plenty and to draw on these reserves in times of need. The outcome of this process will ultimately determine reproductive success, with respect to the number and weight of calves at weaning. Experience indicates that the best feeding systems are those that are simple to operate and robust enough to withstand mistakes, whether imposed by nature or committed by man. FEED ENERGY REQUIREMENTS BY BIOLOGICAL TYPE AND MANAGEMENT SYSTEM Biological types The choice of suckler cow genotype is determined by its technical suitability to the geographical location of the farm, the market potential of its progeny and its availability and cost. Whilst farmers may put these factors in this order of priority, national statistics reveal that availability and cost are, in fact, the prime determinants of choice. Traditionally, the dairy herd has been the main source of suckler cow replacements in the UK, with cross breeds such as the ABSTRACT The key to profitable suckled calf production is to minimise winter feed costs while ensuring that reproductive function, and hence output of weaned calves, is not compromised. This can be achieved by exploiting the cow's ability to store excess nutrients (principally energy in the form of fat) in times of plenty and to draw on these reserves in times of need. By ensuring that minimal levels of body condition score are achieved at key periods during the cow's annual cycle, notably around calving and mating, fertility should not be compromised. Furthermore, an understanding of these relationships, together with the judicious selection of weaning dates, will enable the suckled-calf producer to select genotypes for his enterprise that would otherwise be unsuitable for the geographical location. The ability of the cow to draw on body energy reserves further permits the producer to introduce simple and cost effective systems of flat-rate feeding. Low quality winter forages are frequently deficient in effective rumen degradable protein, and lactating beef cows mobilising large quantities of body fat can sometimes benefit from a supply of digestible undegradable protein. Table 1. Classification of certain beef cow genotypes by their estimated genetic potentials for mature size and milk yield Genetic potential for milk yield (Peak yield: MJ/d/kg Wt.0.75) Genetic potential for mature size (kg) Low (0.3) Moderate (0.7) High (1.0) Small (650) Galloway Blue Grey Shetland Medium (750) Limousin South Devon Limousin x Holstein Large (900) Charolais Simmental Simmental x Holstein Management systems As the suckler enterprise represents just one of two or more farm enterprises in the majority of lowland and upland units, choice of calving date is primarily

CATTLE PRACTICE determined by the ease with which supervision can be provided around calving. Hence most upland herds will calve either before or after lambing in the spring or harvest in the autumn. However, interactions of seasonal and climatic variables can affect cow fertility and calf health and these factors, together with age and season of marketing calves and the provision of labour on the farm, will ultimately determine calving date. With regard to the nutritional requirements of the cow, the total amount of energy required per annum is broadly the same however it is distributed throughout the year. Hence a cow of a given genotype calving in the autumn will have similar net energy requirements as one of the same genotype calving in the spring, but is unlikely to be offered the same levels of dietary net energy during lactation due to the higher cost of conserved forage relative to grass. Instead, the nutritional management of such animals will ensure that body tissue reserves accumulated during the summer (mainly fat) are mobilised during the winter in an attempt to reduce winter feed costs. Such feeding strategies require high standards of nutritional management with regard to the provision of suitable protein supplements and the achievement of minimum targets for body condition score during lactation (discussed later). The traditional age at weaning for the great majority of suckled calves is typically around 10 months of age. This practice, however, is difficult to defend as it has long been recognised that calves can be successfully weaned at 6 months of age with no significant check in growth rate during the postweaning period (e.g. Perks and Turner, 1979). Genotypes with low milk-yield potentials produce little milk after 6 months of lactation (Tables 2a and b), and so virtually wean themselves from their calves. For those with high milk-yield potentials, significant savings in feed costs can be made when cows are weaned at 6 rather than 10 months. For a Simmental x Holstein cow these savings amount to around 6.3 GJ of ME (Tables 2a and b), equivalent to 2.7 tonnes of average quality grass silage (220g/kg DM; 10.5 MJ ME/kg DM) or 560 kg barley (860g/kg DM; 13.0 MJ ME/kg DM). Early weaning also provides an opportunity for thin cows to gain condition prior to calving and is particularly suited to spring calving herds, where calves can be removed from their mothers at yarding. BCVA 2000 In climatic conditions where the ambient temperature is above or below the thermoneutral zone, the increase in MEm requirements for cattle may be as great as 9% for every 10°C above or below 20°C (NRC, 1996). This estimate, however, is simplistic because increases in MEm requirements due to climatic effects are dependent on the physiological state and level of feeding of the animal in question since these affect the heat increment associated with feeding and determine the efficiency of utilisation of ME for growth, lactation and pregnancy. Furthermore, temperature is not the only climatic variable which affects the maintenance requirements of cattle kept outdoors in temperate regions where wind speed, rainfall and net radiation also influence the energy required for maintenance purposes (Bruce, 1980). Our understanding of the thermal requirements of ruminants in temperate climates is sufficiently detailed to allow us to accurately predict the effects of climate on the performance of beef cows and growing calves using mathematical models (reviewed by Bruce and Broadbent, 1989). One model (Bruce, 1980) used by these authors predicts sensible heat loss (climatic energy demand; CED) from the parameters air temperature, wind speed, net radiation and rainfall, and has been used to quantify the benefits of different types of shelter, including housing, shelter belts and woodlands. For example, the model (Bruce, 1980) predicts that in cold, wet and windy conditions a non-pregnant, lactating cow would require 104 MJ ME/day whether kept indoors or outdoors to maintain constant body weight and that this value would not be reduced by housing (Table 3). In contrast, the food energy requirements of a non-pregnant, non-lactating cow would increase proportionately by 0.31 (72 v. 55 MJ ME/day) if it was kept outside rather than housed in the same conditions. The increase in metabolic heat production associated with the increased level of ME intake necessary to support lactation enables lactating animals to be more tolerant to adverse climatic conditions. Thus, animals may remain productive in such circumstances, but this will depend on the provision of adequate levels of food energy during the period of adversity. VOL 8 PART 2 Table 2a. Predicted† (Bruce et al, 1984) annual metabolisable energy requirements (GJ) for spring calving cows. Weaned at 10 months‡ Genetic potential Genetic potential for milk yield for mature size Low Moderate High Small 24.3 26.5 31.4 Medium 27.0 29.6 35.1 Large 30.4 33.3 40.1 Table 2b. Weaned at 6 months‡ Genetic potential Genetic potential for milk yield for mature size Low Moderate High Small 24.3 24.3 26.4 Medium 27.0 27.0 29.6 Large 30.4 30.4 33.8 † For cows maintaining constant post-calving live weight at an average level of body composition (Body Condition Score = 3; Lowman et al, 1976). ‡ Assumptions: Thermoneutral conditions throughout year; M/D of diets = 10.5 MJ/kg DM; ratio of summer to winter energy intake = 2:1.

CATTLE PRACTICE MANIPULATION OF BODY TISSUE RESERVES Faced with seasonal fluctuations in herbage availability and quality, and due to direct effects of photoperiod and temperature on voluntary food intake, nutrient partitioning and basal metabolism (Blaxter and Boyne, 1982; Loudon, 1994; Ball et al, 1996), the ruminant animal undergoes a cyclical pattern of live weight and body composition change. Consequently, the contribution of mobilised body tissue to the metabolic pool varies throughout the year and by physiological state, energy and nitrogen balance. In cattle the mean energy value of 1 kg empty body weight change is in the order of 26 MJ, but this value depends on the condition or empty body weight of the animal and rate at which live weight is lost (Table 4). For cows in good body condition at calving, tissue mobilised during early lactation contains a relatively high proportion of fat and low proportion of protein. In high yielding animals this imbalance in nutrient supply from body tissue, confounded by the fact that cows in good body condition at calving have lower intakes of DM during early lactation, results in individuals becoming deficient in metabolisable protein (MP). In such circumstances, animals respond to the supply of dietary amino acids that escape ruminal degradation by catabolising less body protein, more body fat, and producing higher yields of milk (Whitelaw et al, 1986; Sinclair et al, 1994a; Table 5). BCVA 2000 The body condition scoring system of Lowman et al. (1976) defined six grades (0 to 5), and described each one in terms of the amount of subcutaneous fat cover over the transverse processes of the lumbar vertebrae and around the tail head. Variation in the partition of fat among the main adipose tissue depots between beef cow genotypes is relatively small, the greatest differences residing between beef and dairy cow genotypes (Wright and Russel, 1984). Thus, these authors were able to estimate for a range of beef cow genotypes that one unit of body condition score was associated with a change of 2242 MJ body tissue energy in the mature, non-pregnant and non-lactating animal. Wright et al, (1986) subsequently estimated that each unit of body condition score loss during late pregnancy in beef cows contributes the equivalent of 3200 MJ dietary ME (1.4 tonnes of average quality grass silage or 285 kg barley (described above)), while 1 unit of body condition score gain requires 6600 MJ dietary ME (2.9 tonnes of average quality grass silage or 590 kg barley). Such relationships permit the rationing of beef cows during the winter period. All that is required is a knowledge of body condition score at housing and target condition scores at calving and/or turnout in the spring (Table 6). VOL 8 PART 2 Table 3. Predicted† (Bruce, 1980) food energy required for a 550 kg non-pregnant cow to maintain constant body weight. Climatic conditions Dry/calm‡ Wet/windy‡ Milk yield (kg) 0 7 0 7 Metabolisable energy (MJ/d) 55 104 72 104 Table 4. Composition and energy content of 1kg of live weight/empty body weight change in beef cows Item Fat (g) Water (g) Protein (g) Energy (MJ) Empty body-weight change (Wright and Russel, 1984) 300 kg 497 358 125 22.5 400 kg 600 287 96 25.9 500 kg 704 215 68 29.3 600 kg 808 143 40 32.7 Rate of live weight change (Triggs and Topps, 1981) 0.44 kg/d 743 191 57 31.0 1.06 kg/d 575 286 85 25.0 Table 5. Effects of body-condition score and digestible undegradable protein (DUP) intake on milk yield and fertility in single and twin suckling beef cows offered 80 MJ ME/day (adapted from Sinclair et al, 1994 a and b) Condition score (units) 2.0 3.0 P value DUP (g/kg) 14 31 14 31 Milk yield (kg/day) 9.6 10.7 10.5 11.8 P < 0.05 Serum NEFA (mmol/l) 0.70 0.95 1.22 1.59 P < 0.01 Anovulatory period (days) 34 55 46 36 P < 0.05 Conception rate (%) 50 30 80 60 P < 0.05 Table 6. Target body condition scores for beef cows Calving Mating Turnout Autumn calving 3 2.5 1.5 Spring calving 2.5 2 2 Summer calving 2.5 2.5 2 † Ambient temperature = 5°C; net radiation = 100 W/m2; ‡ Dry = 0 mm rain and wet = 5 mm rain per day; calm = wind velocity of 1 m/s and windy = 9 m/s. Forage quality dictates the energy level that cows can obtain from ad libitum consumption. Low-quality winter forages will only support the non-lactating cow in early and mid pregnancy without moderate to high levels of energy supplements (Table 7). Even then, dietary levels of effective rumen degradable protein (ERDP) may be inadequate, and supplements such as urea or pot ale syrup may be required. Sources of digestible undegradable protein (DUP), such as soya bean meal or fishmeal, may also be required for cows in negative energy balance and mobilising large quantities of body fat.

CATTLE PRACTICE This will ensure that the MP requirements of the animal are met and, in so doing, reduce excessive muscle protein catabolism and promote colostrum quality. Care is required when offering such supplements during late pregnancy, however, to avoid inducing ketosis. In situations of extreme dietary deprivation, or when cows are carrying twin foetuses to term, the provision of some starchy supplement is recommended. Grazed grass will normally meet the lactating animals ME and MP requirements. Supplementation with DUP is only required when moderate quality forages are offered and cows are mobilising large quantities of body fat. In addition to improvements in milk yield, there is evidence that such supplementation can lead to small improvements in fertility, but only when cows are in moderate to good body condition (Sinclair et al, 1994b; Table 5). The supplementation of DUP to cows that are in poor body condition can actually impair fertility. MANAGEMENT BY CONDITION SCORE Fertility A compelling body of evidence now exists to indicate that body condition at calving significantly influences the duration of post-partum anoestrus in beef cows. Moreover, it would appear that it is body condition per se, rather than the pattern of body condition or live weight change during the prepartum period that is the determining factor. The effects of post-partum dietary energy on this interval are negatively correlated with body condition at calving, and the greatest benefits of high intakes of dietary energy are observed in thin cows at calving. However, very thin cows at calving (< 1.5 units body condition) that are offered high-energy diets during the post-partum period are unable to overcome completely the negative effects of low energy intake during the pre-partum period (Lalman et al., 1997). BCVA 2000 The effect of low dietary intakes leading to live weight loss on the interval from calving to first ovulation is greatest in thin cows at calving (Sinclair et al., 1998). Such animals mobilise increasing quantities of lean tissue as body condition decreases below 2.5 units. Body condition score 2, however, appears to be a watershed. Below this score the incidence of nutritional anoestrus increases dramatically with loss in body condition. Suggested target body condition scores at mating (≥ 2 units; Table 6) acknowledge this and, furthermore, recognise the fact that spring calving cows at grass should be in positive energy balance during the mating period. Group management Body condition score at yarding in the autumn is likely to vary considerably within the herd, even for cows of a single genotype managed to the highest standards. Condition score will vary according to parity, physiological status, health and the inherent genetic variation for the trait within any single genotype. In practice many herds will consist of a mixture of several genotypes. There is a good case, therefore, for grouping cows according to body condition for winter feeding purposes. Thin cows and first calvers will benefit particularly from separate feeding and management. First calvers generally compete less well for available trough space and are particularly sensitive to dietary insufficiencies due to the competing needs of pregnancy, lactation and growth. However, the scope for feeding and managing several groups of cows is limited on most farms. Nevertheless, most units should be able to manage at least two groups, one of which should include bulling heifers, first calvers and thin cows. Pattern of feeding The metabolisable energy requirements of a suckler cow vary according to its stage of pregnancy and VOL 8 PART 2 Table 7. Nutritional requirements by physiological status for 550kg suckler cow in moderate body condition, and the capability of forages tomeet these requirements when offered ad libitum Physiological status Forage category Metabolisable energy (MJ/d) Deficiency Supplement Energy density (MJ/kg DM) Forage type Requirement (R)¶ 0.75 R Mid pregnancy (non lactating) 6 to 7 Straw to poor hay 65 50 ERDP DUP† urea, PAS‡ soya Late pregnancy (non lactating) 8 to 9 NH3 treated straw to poor silage 100 75 Starch DUP† barley soya Lactation 10 to 12 Average silage to grazed grass 115 85 - DUP† - soya To maintain constant body weight ‡ PAS = pot ale syrup † Required when animal mobilises body tissue reserves ¶

CATTLE PRACTICE lactation, and the energy density of the diet (Table 7). For example, the daily ME requirements of a 550 kg non-lactating beef cow offered a diet with an energy density of 9.2 MJ ME/kg DM ranges from around 58 MJ at week 15 of gestation to 98 MJ at parturition. The same animal producing 12 kg milk at peak lactation and offered a diet with the same energy density would be estimated to require 130 MJ ME/d. Since the cow does not move abruptly from one of these stages to the next then there is a theoretical need for the level of nutrition to increase and decline gradually. In reality it would be impracticable to change the level of feeding with the frequency that this theoretical consideration implies and fortunately the cow's ability to store excess energy in times of plenty and draw on these reserves in times of need mean that patterns of winter feeding can be greatly simplified. This can be best illustrated using the model of Bruce et al. (1984) for a 550 kg cow offered 14.4 GJ ME over a 26 week lactational period either at a flat rate of 80 MJ per day, or as 65 MJ/d for 4 weeks, 105 MJ/d for 8 weeks and 70 MJ/d for the remaining 14 weeks (Table 8). Cows fed on a flat rate basis can be sustained on 38 kg of average quality grass silage (10.5 MJ ME/kg DM) alone with just a small amount of straw (∼ 1 kg) to satisfy appetite. By contrast in order to offer 105 MJ ME/d, cows fed at a variable rate would require 1.5 kg concentrates in addition to silage. In addition to the requirement for expensive concentrates, variable rate feeding systems are difficult to implement effectively because the physiological status, and hence requirements, of cows in the herd will vary considerably at any one time. Flat-rate feeding strategies are attractive because they are simple, effective and economic to implement. BCVA 2000 and her ability to draw on body reserves in times of need. Management by condition score can significantly reduce winter feed costs while ensuring that reproductive function is not compromised. Geographical location, however, will affect available feed supplies and influence genotype selection; although choice of calving and weaning date can enable some scope for flexibility. Whenever possible, suckler herds should be subdivided by genotype, parity, condition score and calving date and managed accordingly. The most successful feeding systems are those that are simple to operate. ACKNOWLEDGEMENTS SAC receives financial support from Scottish Executive Rural Affairs Department. REFERENCES Ball A. J., Thompson J. M. and Pleasants A. B. (1996). Seasonal changes in body composition of growing Merino sheep. Livestock Production Science, 46: 173-180. Blaxter K. L. and Boyne A. W. (1982). Fasting and maintenance metabolism of sheep. Journal of Agricultural Science, 99: 611- 620. Bruce J. M. (1980). Modelling the climatic energy demand on suckler cows. Animal Production, 30: 449 (abstr.). Bruce J. M., Broadbent P. J. and Topps J. H. (1984). A model of the energy system of lactating and pregnant cows. Animal Production, 38: 351-362. Bruce J. M. and Broadbent P. J. (1989). New techniques in modelling cattle production systems. In: New Techniques In Cattle Production, (ed. C. J. C. Philips), Butterworths, London. Chapter 14: 180-205. Lalman D. L., Keisler D. H., Williams J. E., Scholljegerdes E. J. and Mallett D. M. (1997). Influence of Postpartum Weight and Body Condition Change on Duration of Anestrus by Undernourished Suckled Beef Heifers. Journal of Animal Science, 75: 2003-2008. Louden A. S. (1994). Photoperiod and the regulation of annual and circannual cycles of food intake. Proceedings of the Nutrition Society, 53: 495-507. Lowman B. G., Scott N. A. and Somerville S. H. (1976). Condition scoring of cattle. Rev. Ed. Bulletin, ESCA, No. 6. MLC (1985). Beef Yearbook. Meat and Livestock Commission, Milton Keynes. MLC (1987). Beef Yearbook. Meat and Livestock Commission, Milton Keynes. MLC (1992). Beef Yearbook. Meat and Livestock Commission, Milton Keynes. MLC (1995). Beef Yearbook. Meat and Livestock Commission, Milton Keynes. NRC. (1996). Nutrient Requirements of Beef Cattle (7th edition). National Academy press, Washington, DC, USA. Perks D. A. and Turner P. J. (1979). Comparison of three dates of weaning for lowland single suckled calves. Animal Production, 28: 420 (abstr). Sinclair K. D., Broadbent P. J. and Hutchinson J. S. M. (1994a). The effect of pre- and post-partum energy and protein supply on the performance of single- and twin-suckling beef cows and their calves. Animal Production, 59: 379-389. Sinclair K. D., Broadbent P. J. and Hutchinson J. S. M. (1994b). The effect of pre- and post-partum energy and protein supply on the blood metabolites and reproductive performance of single- and twin-suckling beef cows. Animal Production, 59: 391-400. Sinclair K. D., Yildiz S., Quintans G., Gebbie F. E. and Broadbent P. J. (1998b). Annual energy intake and the metabolic and reproductive performance of beef cows differing in body size and VOL 8 PART 2 Table 8. Predicted (Bruce et al., 1984) performance of a 550 kg cow with a potential mature weight of 750 kg and potential peak milk yield of 0.7 MJ/d/kg Wt0.75 offered 14.4 GJ ME over a 26 week lactational period either at a flat or variable rate. Pattern of feeding Flat rate Variable rate Number of weeks 26 4 8 14 Energy intake (MJ ME/d 80 65 105 70 Live weight at week 12† (kg) 494 510 Minimum live weight‡ (kg) 468 469 Milk yield (kg) 1666 1650 † Cows expected to conceive by week 12 ‡ Occurred at week 26 in both cases CONCLUSIONS In contrast to the dairy cow, the beef cow is rarely treated as an individual but is fed as part of the overall herd. Fortunately, the beef cow can tolerate such relaxed systems of nutritional management because of her relatively low level of performance

CATTLE PRACTICE milk potential. Animal Science, 66: 657-666. Whitelaw F. G., Milne J. S., Orskov E. R. and Smith J. S. (1986). The nitrogen and energy metabolism of lactating cows given abomasal infusions of casein. British Journal of Nutrition, 55: 537-556. Wright I. A. and Russel A. J. F. (1984). The composition and energy content of empty body-weight change in mature cattle. Animal Production, 39: 365-369. Wright I. A., Russel A. J. F. and Hunter E. A. (1986). The use of body condition scoring to ration beef cows in late pregnancy. Animal Production, 43: 391-396. BCVA 2000 VOL 8 PART 2

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 INTRODUCTION Little research has been conducted specifically into the micronutrient needs of beef suckler herds and it will be necessary to draw largely on research performed more cheaply with sheep or with greater prospect of return with the dairy cow. Neglect of the suckler cow is unfortunate in that the suckler herd is theoretically more vulnerable to micronutrient deprivation than either the sheep flock or the dairy herd. Vulnerability stems from low (or absent!) profitability and consequent reliance on cheap forages (eg ammoniated straw) and periods of below maintenance feeding (Sinclair and Suttle, 2000) when the mobilisation of body fat yields energy but little else. Maintenance requirements for Ca, P and Mg to replace endogenous losses via faeces are probably high for bulky, low quality diets. Any economically enforced reductions in disease control procedures may lead to less efficient recycling of P (because of parasitised intestinal epithelia) and an increased demand for antioxidant nutrients (eg Cu, Mn, Se and vitamin E) during microbial infections. The objects of this paper are therefore threefold: firstly, to compare new estimates of minimum mineral requirements (Underwood and Suttle 1999) with the range of mineral concentrations commonly found in forages and by-products fed to suckler herds in the UK (MAFF 1990), secondly to pinpoint the circumstances in which micronutrient deficiencies are most likely to limit production; thirdly, to suggest the most cost-effective methods of intervention, where they are needed. MICRONUTRIENTS: THE BUCK STOPS HERE Before embarking on any exercise of this kind it is important to put micronutrients alongside other possible - indeed more probable - explanations of poor health or performance, the buck should stop rather than start with micronutrients. Alternative explanations in decreasing order or probability are:- 1. Inadequate intakes of digestible organic matter. 2. Imbalance between energy and protein supplies for the rumen microbes. 3. Poor milk intakes by the suckling due to maternal undernutrition (for reasons 1 and/or 2). 4. Infections by microbes, viruses or gut parasites (immunity in the adult wanes around parturition). 5. Environmental stress (exposure to cold, wind, rain etc). 6. Mineral imbalance. Unfortunately producers often prefer to be told that mineral imbalance is to blame because it suggests natural causes rather than poor management to be responsible for poor performance. THE MINERAL NEEDS OF SUCKLER HERDS The latest estimates of dietary requirements for Ca, P, Mg, Cu and Zn are given in Table 1. Such estimates are not necessarily minimum requirements although they are as close to the minimum as it is possible to get at present. Requirements for Co, I, Mn and Se are given separately (Table 2) because they can only be given as single approximate ranges for all classes of animal, either because factorial modelling has not been used or (as in the case of Se) models show little variation in need. Requirements are generally better given as marginal bands because there are no magical thresholds below which health and performance are impaired, dietary energy and protein value (Sinclair and Suttle 2000), interactions with other elements Suckler cow nutrition: II Minerals and vitamins Suttle N.F1., Sinclair K.D2., 1Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ. 2Department of Applied Physiology, Scottish Agricultural College, Craibstone Estate, Buckstone, Aberdeen, AB21 9YA. ABSTRACT Comparisons of minimum mineral requirements with the range of mineral concentrations commonly found in forages and by-products fed to suckler herds in the UK identifies the micronutrient deficiencies most likely to limit production. Supplies of Mg, Cu, and Se and the vitamins D and E in winter are the most likely to be inadequate, while K may be present in excess, increasing risk of milk fever as well as hypomagnesaemic tetany. Allowing condition score to fluctuate decreases mineral needs during dry periods and increases them during lactation. With profitability questionable, there is a case for exploiting the tolerance of stock towards marginal deficiencies, addressing specific needs when they become life- or production- threatening, targeting groups most at risk (the heifer, the aged, the underweight or the immunosuppressed periparturient cow) and using inorganic rather than 'organic' mineral sources, unequal in cost but equal in efficacy.

CATTLE PRACTICE and stressors all governing the daily amounts and dietary concentrations which are needed. The single values given for Ca and P in Table 1 allow the skeletal reserve to provide the necessary safety allowances. Mg requirements are given for cattle on pastures or winter forages varying in K concentration to illustrate the importance of the K X Mg antagonism, requirements for dry diets are only 2/3rds of those shown. The Cu requirements presented are for cattle grazing pastures low in Mo (< 1.5mg Mo/kg DM): in the rare event of Mo levels exceeding 2, requirements might be doubled, whereas with fresh forage of normal S concentration (c. 2.5g/kg DM) they are approximately halved because of changes in the efficiency of absorption (ACu, Fig 1). Conservation lowers the inhibition of Mo on ACu but the effect of S in silages is not diminished (Suttle,1986): the permutations in Cu requirement are therefore endless! BCVA 2000 MINERAL PROVISION IN COMMON FEEDSTUFFS The mineral composition of some common UK foodstuffs is summarised in Table 3. The recorded variation about the mean is just as important as the mean value when assessing possible mineral provision from feed resources on a particular farm. For simplicity, values are only given for fresh grass; mineral concentrations for silage are usually slightly higher and those for hay slightly lower than the means for fresh material. Contamination by soil can greatly increase Co, Fe and Mn, all of which are partially available for absorption and/or antagonisms. RISKS OF MINERAL IMBALANCE Comparisons of data in Table 3 with Tables 1 and 2 indicate that lack of Ca or P should rarely be a problem for the relatively low-yielding suckler cow at pasture, assuming the continuance of current fertilizer practice. If early weaning is practised, an extended dry period with very low requirements should allow the cow ample time to replenish any loss of skeletal reserves. In autumn and winter, mixtures of sugar beet pulp with brewery or distillery spent grains offset the former's lack of P and the latter's lack of Ca. The position with Mg is different with provision from pasture and conserved forages much closer to need and with a smaller and less accessible skeletal reserve to offset any deficit. The marginal nature of Mg supplies is born out by a report of an exponential decline in plasma Mg with age in a suckler herd (Suttle et al 1980 Fig 2) and the high frequency of reports of hypomagnesaemic tetany (HGT) in the SVIS. The decline in Mg status is probably due to cumulative dietary deficits and also a genuine 'age effect', reflecting the declining accessibility of the skeletal reserve in older cows; this age effect is likely to increase susceptibility to milk fever, just as it does in the dairy cow. Provision of brewers or distillers grains over winter provides additional Mg of dubious availability; although these VOL 8 PART 2 Table 1. Approximate dietary requirements of the suckler herd for macro elements, Cu and Zn (from Underwood and Suttle, 1999). Production level Diet quality Food intake Ca P Mg# Cu* Zn kg DM/d g/kg DM mg/kg DM Growing 100kg 0.5kg/d M 2.0 6.5 4.1 1.2-1.6 7 11-14 300kg 0.5kg/d M 4.6 3.7 2.5 1.3-1.5 10 11-14 Adult 550kg 0 L 9.0 1.9 1.5 1.8-2.3 8 9-12 Pregnant Term 1 calf M 9.3 3.2 2.3 1.5-2.0 15 9-12 Lactating 10kg/d M 9.0 3.5 2.7 2.0-2.5 11 13-16 # The lower and upper limits for each range are calculated for forage with 25 and 50gK/kgDM, respectively, assuming absorption coefficients for Mg of 0.17 and 0.13. * Values are calculated for forage based diets assuming that 0.03 of the dietary Cu is absorbable (ACu); the large influences of Mo and S on requirement via changes in Acu can be gauged from Fig 1; diets with a Fe:Cu ratio in the 50-100 range should be considered marginal. Co I Mn Sc Summer Winter 0.04-0.06 0 0.05-0.1 0.1-0.2 10-20 0.03-0.05 + 1.0 (?) 2.0 (?) Table 2. Marginal dietary requirements of sheep and beef cattle for other trace elements (mg/kg DM) Values for iodine allow for an effect of season and uncertain but large influence of diets containing (+) or not containing (0) goitrogens. Figure 1. Effects of molybdenum and sulphur concentrations on the absorbability of copper from fresh grass 0 1 2 3 4 5 6 7 0246 Grass Mo (mg/kg DM) Absorbable Cu (%) S 1 S 3 g/kgDM

CATTLE PRACTICE by-products are low in K, the dominant factor responsible for the poor absorption of Mg from most forages (Underwood and Suttle 1999). When used as the sole winter feed, Mg deficiency can arise (Lewis and Lowman 1989), possibly because transit through the primary absorption site (the rumen) is rapid. Mixture of spent grains with the ensiled and pressed forms of beet pulp (1.4-1.9gMg/kgDM) provides more Mg and less K than the dried molassed form (Table 3). Risks of milk fever (Goff and Horst, 1997) as well as HGT are increased by commonly encountered levels of forage K (30g+/kgDM) which are sufficient to shift acid-base balance and restrict mobilisation of Ca and Mg from the skeleton. The use of fertilizer K in spring should be restricted to the amount needed to maximise grass growth (i.e. herbage K of 25g/kgDM). Beet and cane molasses are rich sources of K (40-50g/kgDM) and root crops not far behind (20-40). BCVA 2000 RISKS OF TRACE ELEMENT IMBALANCE As far as trace elements are concerned the most critical element appears to be Cu. The average pasture just meets average need but provision of byproducts or protein (not NPN) supplements during lactation should more than meet the additional need. The high apparent need in late pregnancy (Table 1) is due to an allowance for the establishment of a good reserve of Cu in the liver of the newborn calf. Failure to meet that requirement need not prejudice calf survival but survival is arguably the most important production target and a cow which cannot provide its offspring with a reserve will probably produce milk low in Cu. Although Mo is the most widely discussed antagonist of Cu, in the field it is probable that wide ratios of Fe:Cu cause imbalance more frequently than narrow Cu:Mo ratios (<3.0) Selenium is the next most limiting trace element to Cu, average Se level in pasture coinciding with the upper limit of requirement. Many have claimed that more Se is needed to ensure protection from infections but these reports come mostly from the USA and involve intensively managed dairy herds of marginal vitamin E status. Studies with beef herds in Australia suggest far greater tolerance of low Se status (Langlands et al 1989). Two of the rare reports of Se-responsiveness in growing cattle have featured a concomitant Cu-deficiency (Gleed et al 1983; Koh and Judson, 1987) and there is a need be on the look out for dual deficiencies, given the marginal Cu status of our sucker herds, which can also decline with age (Suttle et al 1980). Recent work in N. Ireland on commercial silage or experimental diets marginal in I (c. 0.05mgI/kgDM) VOL 8 PART 2 Table 3: Mean mineral composition of common components of the suckler herd diet (data from MAFF 1990, Underwood and Suttle 1999 and Suttle ,unpublished): standard deviations in parenthesis Ca P Mg Cu I Mn Se Zn (g/kg DM) (mg/kg DM) Grass 5.4 (1.7) 3.0 (0.7) 1.6 (0.5) 7 (2.6) 0.2 - 180 (55) 0.05 (0.02) 32 (5.5) Straw (NH3-treated) 4.6 (1.8) 1.1 (7) 0.6 (0.24) 2 - 29 - 14 Fodder beet 2.8 (2.4) 1.8 (0.27) 1.6 (0.3) ----- Barley 0.9 (0.6) 4.0 (0.5 1.2 (0.2) 4 (1.5) 0.10 18.5 (3.6) 0.10 33 (8.5) Brewers grains 3.5 (1.4) 5.1 (1.0) 1.7 (0.36) 19 (9.2) 31.0 (4) 73 (12.5) Distillers dark grains 1.7 (0.3) 9.6 (0.8) 3.3 (0.3) 4 (16.8) 0.2 (0.06) 35 (0.75) 0.18 55 (4.7) Sugar beet pulp (molassed) 7.6 (2.0) 0.8 (0.15) 1.1 (0.19) --- - Soya bean meal (extracted) 3.9 (1.6) 7.4 (0.44) 3.0 (0.33) 16 (2.6) - 38 (10.7) 0.30 (0.19) 49 (9.9) Figure 2. Apparent effect of age on magnesium status of beef suckler cows 0.5 0.6 0.7 0.8 0.9 1 0 2 4 6 8 10 Age (years) Plasma Mg (mmol/1

CATTLE PRACTICE have failed to show benefits from I supplementation in terms of calf survival, despite small decreases in thyroid weight and cellular hypoplasia (Mee et al 1995, McCoy et al 1997). Atmospheric deposition of I of marine origin has a dominant influence on herbage I, giving high levels in winter and early spring pasture. Few parts of Northern Britain are sufficiently far from the coast (> 50km) not to benefit (this applies also to deposition of Na and S) and only autumn calving herds or those given late cut silage are likely to need additional I. Co deficiency is rarely seen in cattle. If there is a history of Coresponsiveness in the more susceptible lambs on a mixed stock farm, there may be a small benefit from supplementing cattle with Co but they can ingest plenty of utilisable Co in soil contaminating pasture and forage. Risks of Co deprivation are highest on alkaline soils, high in Mn (>1000mg/kgDM) where Mn is also likely to be poorly available to plants and stock. Deficiencies of Mn and Zn are almost unheard of in the UK. RISKS OF VITAMIN IMBALANCE Requirements for the fat soluble vitamins, A, D and E, are poorly defined, and those for E probably underestimated by as much as 50%. Seasonal fluctuations in vitamin E and D status lead to minimal levels in winter and early spring for different reasons. Although spring grass is rich in vitamin E it is also rich in polyunsaturated fatty acids (PUFA) which,when peroxidised in the tissues, 'consume' the vitamin. Thus median plasma tocopherol levels in samples submitted to the VIC stay low until June (Fig 3) and these low levels are probably matched by low levels in milk. The problem with vitamin D is one of lack of sunlight and therefore should get worse the further north that the farm is situated and on farms with a northerly aspect. Where supplements are offered, vitamin D provision is usually generous but particularly important for the older cow. Provision of E is often miserly in relation to a much greater daily need (g v mg) and the preferred route for supplementation is oral rather than parenteral because the amounts provided in commercially available injectable preparations are trivial. Clients should be advised to compare concentrations of E in mineral/vitamin mixtures and go for the highest specification (c.2000iu/kg), while ensuring that mineral balance is appropriate. Provision of vitamin A in commercial mixes is usually excessive, unneeded (except on straw-based rations) and may lower vitamin E and D status whereas supplementation of the dam with vitamins E and D can improve immune status in offspring. BCVA 2000 IMPACT OF MANAGEMENT BY CONDITION SCORE The strategy of allowing the lactating suckler cow to meet a significant portion of its energy need from endogenous reserves (Sinclair and Suttle 2000) has a number of implications for mineral and vitamin nutrition, since adipose tissue is poor in minerals and rich in fat soluble vitamins (A, D and E), provided there has been a season of plentiful supply. Thin cows have less capacity to store A, D and E than fat cows. When cows decline in condition score from an acceptable starting point in terms of vitamin reserves, A, D and E should be mobilised. By contrast, dietary requirements for minerals are probably some 10% higher than those given in Tables 1 and 2 when cows are fed to lose condition score. The use of supplemental N as urea or ammonia (in straw treatment) will have a similar effect, raising production capacity without furnishing more minerals. It should be noted that straw is a poor source of many minerals, notably P, Mg and Cu (Table 3). Dry periods which allow recovery of body condition are likely to be periods of low need for minerals, other than Ca, P and Cu which can usefully be stored. ASSESSING THE DEGREE OF MICRONUTRIENT IMBALANCE Given the uncertainties of knowing how much micronutrient an animal needs and how much the diet (or environment) can provide, great importance lays in the assessment of micronutrient status in the animal. A schematic sequence of biochemical events is given in Fig 4 and it helps to explain the limitations of the commonly used indices of dietary imbalance. Unfortunately, few of the biochemical measures currently used to assess status reflect the likelihood of production-limiting dysfunction. Most are indices VOL 8 PART 2 Figure 3. Median vitamin E status Circle = cattle: Triangle = sheep: Line = England + Wales: Dash = Scotland

CATTLE PRACTICE of reserves (liver or bone biopsies) or amounts being transferred to and from the transport pool (blood). Again it is important to use marginal bands for interpretative purposes but the UK seems to have lagged behind the rest of the world in this regard, retaining a single threshold value or clinically anonymous reference range for distinguishing the abnormal from the normal: the outcome is an overdiagnosis of micronutrient disorders. Table 4 gives marginal bands for the interpretation of the commonly used - though far from perfect - indices of mineral status. The three tier system has its own BCVA 2000 arbitrary elements, dividing up what is a continuously variable relationship: usage would result in less 'certainty' but more accuracy and honesty in diagnosis. When the mean for a set of samples falls within the marginal band there is a possibility of benefit from supplementation with the mineral in question, the nearer the mean is to the lower limit, the greater that possibility, the nearer to the upper limit, the less that possibility. Variation about the mean can be as useful as the mean itself, a point returned to later. VOL 8 PART 2 Nutrient pool 1 2 100 Storage Transport 3 Function Marginal supply 4 Clinical signs 0 depletion deficiency dysfunction disease Time Figure 4. Sequence of patho-physiological changes in livestock given an inadequate mineral supply: for Cu, the sequence is 1. Depletion of liver store, 2. reduction in caeruloplasmin and Cu in plasma, 3. fall in cuproenyme activities in tissues, 4. loss of coat colour, swollen epiphyses, stunted growth or infertility; for some elements (e.g. Ca and P), storage and function are linked by bone strength; for elements with small or slowly mobilized stores (Zn and Se) curves 1 and 2 are superimposed or interposed; for all elements there is usually a zone of marginal supply (shaded area) where mineral-dependent functions begin to fail but the animal appears healthy. Table 4. Marginal bands for commonly used biochemical indices of micronutrient status in cattle in serum (S, per litre) or tissue (T, per kg DM) Macro minerals Trace elements Ca P mmol Mg Cu μmol I nmol Mn nmol Se nmol Zn nmol Vitamin B12 nmol S 1.3-2.0 1.0-1.5 0.5-0.75 3-9* 8-20 90-108 100-120 60-90 0.25-0.5M T 180-20R (g) 90-110R (g) 3.3-4.0 (g) 100-500L* ( μmol) 1.2-20TH (g) 1.0-1.4R (mg) 0.6-1.0* (μmol) 50-70R (mg) 280-340L (pmol) M= milk; R = Rib (cortical bone); L = Liver; TH = thyroid *Newborn calves often require separate limits: serum Cu - the range above is normal liver Cu - 750 to 3150 is marginal liver Se - values 3x higher in foetus

CATTLE PRACTICE As far as criteria for individual elements are concerned the following points - discussed in more detail by Underwood and Suttle (1999) - need emphasis. Co. Vitamin B12 is not reliably estimated by current methods in bovine plasma or serum samples: more use should be made of milk B12 assays. Cu. Diagnostic use of caeruloplasmin (CP): Cu ratios in plasma has no sensible physiological or biochemical basis, but merely exaggerates the incidence of Cu problems. Insufficient is known about the relationship between superoxide dismutase (SOD) activity results from particular laboratories and animal health for ESOD values to assist diagnoses. I. Total protein bound I is being widely used to assess I status but again diagnostically significant ranges are unknown and those commonly used are probably too high. Se. More use should be made of plasma Se as it is a better indicator of current dietary supply than erythrocyte GSHPx, the former reflecting transport and the latter storage. Vitamin E. Plasma α tocopherol is a poor indicator of the risk of peroxidative damage to cell membranes, the ultimate site of dysfunction in E (and Se?) deficiency. Values fluctuate markedly around parturition in the cow and around weaning in the calf: low values should be confirmed by resampling after 7-14 days. Exposure to oxidants such as PUFA can 'consume' α tocopherol, giving low plasma values without necessarily causing myopathy. A wide marginal band of 0.5-3.0umol/l is called for as opposed to the current dividing line of 2.3umol/l. METHODS OF INTERVENTION Specific rather than general supplementation Since most minerals are likely to be present in adequate concentrations in the suckler cow diet, provision of free access to complete mineral mixtures (costing around £10-20/head p.a.?) may be wasteful and ineffective. Failure to give complete cover may be due in part to the well known individual variation in uptake of such mixtures (Underwood and Suttle, 1999). A study in N. Ireland showed that provision of Mg-rich mineral blocks did not raise marginal plasma Mg levels in beef herds (McCoy et al 1996). Shortages of Mg could be offset by sprinkling MgO or MgCl2 sparingly over the silage or other roughage in autumn or spring so as to provide an extra 1g Mg/kg DM (ie 1/3rd of the old recommended dose per head which was sufficient to shift acid-base balance!). Shortages of Cu are best met by oral dosing with CuO particles in spring while Se can be economically and effectively given in the BCVA 2000 anthelmintic drench. While it is uncommon for adult cattle to be drenched, there is a temporary waning of immunity around calving which often coincides with the seasonal rises in larval burdens on pasture. Removal of worms may improve the absorption of protein and some minerals (e.g. P and Cu) at times of maximum need. One point in favour of continuous provision of mineral is that they can provide the best vehicle for administering vitamins, particularly E. Injectable preparations of vitamin E provide too little in relation to daily need (c. 500mg/d for a cow) and repeated injections may not be possible for fear of overdosing with the Se commonly included in the one product. Short periods of feeding mineral/vitamin mixtures for one month either side of calving might be a suitable compromise. Inorganic v organic mineral sources In these harsh economic times, it is scandalous that producers should be enticed to spend money unnecessarily on expensive 'organic' sources of trace elements for which there is no scientifically proven nutritional advantage. Unfortunately the 'sales pitch' which goes with organic sources falls on receptive ears and - to the uninitiated - it seems so plausible. The tale goes like this: "most essential minerals are prone to antagonists which increase needs and precipitate disorders; protect the mineral supplement from antagonists and all problems would be controlled; by mimicking nature's very own absorptive agents (peptide complexes), control is assured!". Unfortunately these very agents would have been present and found wanting in the natural situation that they address, destroyed by sulphide in the rumen or by the acid abomasal pH (Kratzer and Vohra 1986). Once dissociated, organic sources are on equal terms with inorganic sources which reach the intestine in a peptide-rich milieu, the very milieu which manufacturers so carefully engineer prior to feeding when they hydrolyse feed proteins and add trace minerals to produce 'metalosates'. Thus there are no theoretical grounds for expecting the commonly used method of protection to work. In the relatively rare cases where organic and inorganic sources of a mineral have been directly compared by experiment, differences have rarely been statistically significant and for every instance of 'benefit' it is possible to cite as many instances of 'detriment', usually the better designed and statistically analysed studies (for reviews on Co, Cu, Mn and Zn, see Underwood and Suttle 1999). Metabolism for some elements, notably Se, can certainly be changed by providing organic sources but since inorganic sources are rapidly incorporated into selenocysteine in vivo, no good is served by pre-empting nature. While organic Cr sources have insulin-potentiating and cortisol-lowering properties, which have been associated with improved immune responses in VOL 8 PART 2

CATTLE PRACTICE transport-stressed feedlot calves, inorganic Cr sources also assist insulin (Kegley et al 1997), suggesting that they are metabolised into potent complexes in vivo. Assessing benefits of intervention The best diagnosis of the need to intervene is provided by a measurable benefit to a specific supplement but the benefit may not be immediately obvious from a simple comparison of mean performance of treated and untreated groups. In searching for benefits of dosing lambs on improved Scottish hill pastures with Co, Cu or Se, statistically significant benefits in the sizeable matched groups (25 pairs of twin lambs, one of which was treated) were few and far between (Suttle et al, 2000). There were however some surprising differences between the relationships between final and initial liveweights between groups which suggested that intervention had benefited some lambs. The phenomenon is illustrated in Fig 5 for a trial involving Se. Final weight was poorly correlated with initial weight in treated lambs, presumably because the smallest lambs were in need of more Se and showed compensatory growth when it was given. This is typical of most micronutrient disorders where there is a vulnerable 'tail' to the population, which attracts the attention of the stockman. Depending on the size of the 'tail', it may be worth considering the selective treatment of those who fail to meet a target weight. Heifers are another vulnerable group with cumulative production needs, exceeding those in Tables 1 and 2, with the approach of first calving and a second conception. If they currently perform well, this augurs well for the mineral status of the rest of the herd but their nutrition is often neglected until a perilously close stage is reached. BCVA 2000 CONCLUSIONS Risks of mineral imbalances causing loss of production or ill health in livestock are generally exaggerated but there is a need to be watchful in suckler herds. Flexible interpretation of biochemical indices of mineral status of animals and the use of responsiveness to specific supplements to confirm diagnosis provides the surest approach. Multiple deficiencies are rare and 'complete' supplements rarely complement any local deficiencies satisfactorily. There may often be an economic case for looking out for the most likely shortfalls -in Mg, Cu and Se - and treating them specifically with minimal inputs in cheap forms, avoiding 'chelates' which are of no proven superiority. REFERENCES Gleed P.T., Allen W.M., Mallinson C.B., Rowlands G.J.,Sansom B.F.,Vagg M.J.and Caswell R.D. 1983 Vet. Rec.113: 388-92. Goff J.P., Horst R.L., 1997 J.Dairy Sci. 80: 176-86. Kegley E.B., Spears J.W., Eisemann J.H., 1997 J.Dairy Sci. 80: 1744-50. Koh T. S., Judson J.G., 1987 Vet. Res. Comm. 11: 133-48. Kratzer F.H., Vohra P.H., 1986 Chelates in Nutrition, CRC Press, Boca Raton, Florida Langlands J.P., Donald G.E., Bowles J.E., Smith A.J., 1989 Aust. J. Agric. Res. 40: 1075-83 Lewis M., Lowman B.G., 1989 Anim. Prod.48: 656 Mee J.F., Rogers P.A.M., O'Farrell K.J. et al, 1995 Vet.Rec. 137: 508-12 McCoy et al 1996 McCoy M.A., Smyth J.A., Ellis W.A., Arthur J.R., Kennedy D.G., 1997 Vet.Rec. 141: 544-7 and et al, 1997) Sinclair K.D., Suttle N.F., 2000 Cattle Practice (in press) Small J.N.W., Burke L., Suttle N.F., Bain M.S., Edwards J.G., Lewis C.J.,1996 Proc. XIX World Buiatrics Cong.,Vol.2: pp413-5 Suttle N.F., 1986 Vet.Rec. 119: 148-152. Suttle N.F., MacPherson A., Bremner I., Linklater., K.A., (2000) J. Agric. Sci. (in press) Suttle N.F., Field A.C., Nicolson T.P., Mathieson A.O. Prescott J.H.D., Scott N., Johnson W.S., 1980 Vet. Rec. 106: 302-4 Underwood E.J., Suttle N.F., 1999 The mineral nutrition of livestock, 3rd Edition, CABI International, Wallingford VOL 8 PART 2 Figure 5. Relationships between initial and final liveweight in twin lambs given (b) or not given (a) Se by injection a. Untreated lambs b. Se treated lambs Initial kg

CATTLE PRACTICE BCVA 2000 VOL 8 PART 2

BCVA 2000 CATTLE PRACTICE VOL 8 PART 2 INTRODUCTION This paper follows on from Cattle News 1999 Parts 1-3 published in the June 1999 issue of Cattle Practice. The material covered here is taken from the UK Vet's Cattle News columns written in the second half of 1999. In writing the BCVA Cattle News column it is the author's aim to provide a summary of some of the more interesting, and topical, recent publications related to Cattle Health and Production. NEW AND FORGOTTEN VIRAL DISEASES There seems to be a constant stream of new disease syndromes, newly recognised pathogens and ever changing epidemiology of known diseases for the cattle practitioner to contend with. BSE, necrotising enteritis and congenital chondrodystrophy in suckler calves, Influenza A and lungworm in adult cattle, to name but a few. While viruses such as RSV, BVDV and BHV-1 are common and cause significant economic losses, rarer viruses also need consideration. This is the message in a paper that draws attention to bovine parvovirus as a cause of enteric disease in young calves and reproductive losses in breeding cattle, and adenovirus as a cause of respiratory and enteric disease, and a weak calf syndrome (Ellis 1998). The paper also discusses the importance of malignant catarrhal fever, encephalitic herpesviruses, bovine coronavirus as a respiratory and enteric pathogen, bovine immunodeficiency virus and viral pathogens known or thought to be exotic to the UK, including bovine leukosis, vesicular stomatitis and blue tongue. To underline that potential "new" pathogens are out there, lung samples from 6 of 100 cases of bovine respiratory disease and 4 of 30 aborted foetuses from Manitoba, Canada were found to be PCR-positive for a circovirus (Nayar and others 1999). Although some cases were also positive for RSV or BVDV the presence of the circovirus was considered to be significant because of similarities between this virus and a pathogenic porcine circovirus. CYTOLOGY Cattle clinicians looking to enhance their diagnostic skills without the use of prohibitively expensive laboratory tests, or high-tech equipment, may be interested in two recently published review papers on cytology (Whitney and others 1999a & b). The first of these papers covers the general principles of specimen collection, handling and interpretation, before going on to discuss the use of cytology in solid tissue masses and peritoneal and pleural fluid. The second paper covers collection, handling and interpretation of synovial fluid, CSF, tracheal washes and bronchioalveolar lavage specimens. These papers outline how a cattle clinician with little specialist knowledge or laboratory equipment can use cytology as an aid to diagnosis. A LOAD OF BULL Previous work has shown that in beef cows, exposure to the bull hastens the resumption of postpartum ovarian activity and expression of oestrus. However, a recent paper looking at the physiological effect of postpartum exposure of high producing (9764 ± 140 kg milk/lactation) Holstein dairy cattle to the bull has produced unexpected results (Shipka and Ellis 1999). The researchers used plasma progesterone (P4) assays to assess ovarian activity in the postpartum period. Their study showed that postpartum ovarian reactivation, indicated by the first sustained rise in P4 was later (P=0.02) in cattle given continuous or twice daily "over-the-fence" exposure to a bull than those isolated from the bull. The isolated cows had higher P4 concentrations (P=0.05) and tended to complete their first cycle sooner, although not significantly sooner (P=0.08) than cows exposed to the bull. The results of an experiment to test the hypothesis that mating stimuli in beef heifers improves pregnancy rates to AI have also recently been reported (Rodriguez and Rivera 1999). One hundred and seventy-eight cows and heifers were randomly assigned to three groups, and given differently timed mating stimuli. The mating stimulus was a single mating with a sterile vasectomised bull. The pregnancy rate differed among the groups; cows given a mating stimulus at the time of oestrus detection had an increased pregnancy rate (60.0%), compared to those given a mating stimulus immediately after AI (25.4%) and those given no mating stimulus (35.6%) (P<0.01). The authors conclude that there is evidence of a biostimulatory effect of sterile mating at the time of oestrus detection on pregnancy rate to AI. The reason for this effect was not determined, although there is speculation about the effects of clitoral stimulation or the role of accessory sex gland secretions in sperm transport. It is interesting to consider that a vasectomised bull may be doing more for herd fertility than simply aiding in oestrus detection. Cattle News 1999 Parts 4-6 Barrett D.C., Department of Veterinary Clinical Studies, University of Glasgow Veterinary School, Bearsden Road, Bearsden, Glasgow, G61 1QH.

CATTLE PRACTICE PUBLIC HEALTH The public health issues relating to Escherichia coli O157:H7 and salmonella cannot have escaped the notice of many over recent months. A Canadian paper looking at the prevalence of verotoxins (VT1, VT2) from verotoxin-producing E. coli, E. coli O157:H7 and salmonella in the faeces and rumen contents of slaughter cattle over a one year period makes interesting reading (Van Donkersgoed and others 1999). The main results are summarised in Table 1. The prevalence of E. coli O157:H7 was highest in BCVA 2000 quantification of this effect allows economic analysis of the impact of disease and thus better targeting of scarce disease prevention resources. The relationship between overfeeding and overconditioning in the dry period and the problems of high-producing dairy cows during the postparturient period is reviewed in a paper by Rukkwamsuk and others 1999). This excellent review of 125 papers covers almost all aspects of the fatty liver syndrome. Recent developments such as the role of leptin, a 16-kDa protein secreted by adipocytes, in the regulation of food intake and energy metabolism are discussed. The relationship between overconditioning at calving and diseases such as milk fever, displaced abomasum, ketosis and infectious diseases is reviewed, as is the relationship between negative energy balance and reproduction. This paper concludes that negative energy balance in the postparturient dairy cow induces changes in a great number of biochemical, endocrinological and metabolic pathways. A study of the risk factors for abomasal displacement in dairy cows has also recently been published (Rohrbach and others 1999). This retrospective case-control study used 75 cows matched with controls on the basis of herd of origin, breed, age, and calving date. The case cows were found to be significantly more likely to have had RFM, ketosis, a stillborn calf, metritis, twins or milk fever than controls. Dystocia, mastitis and milk production during the previous lactation period were not associated with abomasal displacement. The main reported clinical signs of displaced abomasum were anorexia (88%), decreased milk production (33%) and diarrhoea (23%). There is abundant evidence that feeding practices during the dry and early lactation periods affect the occurrence of abomasal displacement. Together the above reviews further underline the vital importance of dry and transition cow feeding in the health and welfare of the modern dairy cow. TUBERCULOSIS With the debate about how best to control TB within the UK continuing, a Canadian paper reports an investigation into the between-herd spread of Mycobacterium bovis in cattle and cervids between 1985 and 1994 (Munroe and others 1999). Two risk factors were identified: increasing herd size, and the reason why a herd was investigated as part of the outbreak. When compared to testing all herds within a specified radius of a reactor/positive herd, the odds ratios for herds which had purchased animals from a reactor/positive herd, for herds with fence-line contact with a reactor/positive herd, and herds which had been a source of animals for a reactor/positive herd were 57.8, 31.8 and 14.9 respectively (P<0.001). VOL 8 PART 2 Table 1. Verotoxins (%) E. coli O157:H7 (%) Salmonella spp. (%) All faecal samples 42.6 7.5 0.08 All rumen contents samples 6.4 0.8 0.3 Batches of yearling cattle (one or more faecal sample positive) 80.4 33.6 0.7 Batches of cull cows (one or more faecal sample positive) 78.0 6.0 0 the summer months. The risks to human health from handling and/or eating meat contaminated with verotoxins, E. coli O157:H7 or salmonella are obvious. The current UK epidemiological study on E. coli O157:H7 (Paiba and others 1999) should greatly add to our knowledge in this area. However, those of us working regularly up to our shoulders in bovine faeces may also like to reflect on the risks we take, or think twice before sucking on a stomach tube when aspirating rumen contents! METABOLIC AND METABOLICRELATED DISEASES A substantial review of the effects of disease on milk production in dairy cows has recently been published (Fourichon and others 1999). This article covers the estimation of milk losses as a consequence of dystocia, stillbirths, milk fever, retained foetal membranes (RFM), metritis, cystic ovaries, ketosis, displaced abomasum and locomotor disorders. While the data reviewed are far to numerous to summarise here, some simplified findings are worthy of note. For example, milk fever and cystic ovaries were not associated with yield losses and less than half the studies found losses associated with dystocia, RFM and metritis (≤2.5 kg/day). More than half the studies found losses associated with stillbirth, ketosis and locomotor disorders (≤1.3 kg/day across the lactation, 2.6-5.7 kg/day short-term and 1-7 kg/day on the day of diagnosis). All the studies investigating effects of displaced abomasum found losses (3.5-10.9 kg/day across 80 days in milk, or 0.8-2.5 kg/day across the lactation). While it may seem obvious to some that these diseases affect production,

CATTLE PRACTICE While the specific findings conveyed in this paper may not be applicable in the UK, the odds ratios reported for 'in-contact' herds provides some food for thought when considering possible changes to our current TB monitoring programme, accepting, of course, that the Canadians may not have the same wildlife reservoir problems that we have. PAIN AND WELFARE In these days of increasing concern about animal welfare in food-producing animals it does no harm occasionally to consider if established practices could not be improved. Two papers on pain management while disbudding calves do exactly that. The first (Grøndahl-Nielsen and others 1999) describes the behaviour, plasma cortisol and heart rate of 4-6 week-old calves during and after dehorning with and without the use of sedation (xylazine 0.2 mg/kg and butorphanol 0.1 mg/kg i/m) and analgesia (2% lignocaine; cornual nerve block). The conclusion, not unexpectedly, is that the routine use of a cornual nerve block improves the welfare of young calves subjected to dehorning with a hot iron, and that sedation alone is not an acceptable alternative to the cornual nerve block. The second paper on this subject comes from New Zealand (McMeekan and others 1999). Here eight behaviours were monitored, from two hours after treatment, in 3-4 month-old calves dehorned with and without local anaesthesia and/or a non-steroidal anti-inflammatory drug. The behaviour of calves dehorned after both a local anaesthetic (cornual nerve block) and a non-steroidal antiinflammatory agent (3ml of 10% Ketoprofen i/v) was similar to controls. From two hours post-dehorning, when the effects of the lignocaine would be expected to be wearing off, the behaviour of calves given only local anaesthesia or systemic analgesia prior to dehorning was similar to that of calves dehorned without any pain relief. These results suggest that calves should be given both a local cornual nerve block and a systemic analgesic before dehorning, in order to alleviate the pain associated with the procedure. While it is a legal requirement to use a cornual nerve block when disbudding or dehorning in the UK, how many of us regularly also administer analgesics ? MASTITIS The relationship between somatic cell count (SCC) and milk production losses was studied by Koldeweij and others 1999). They used 18,131 weekly test-day milk yield records and SCC data from 274 cows in their analysis. The average milk yield was 19.7 kg/day in the first lactation and 22.0 in later lactations. The geometric mean of SCC was 63.1 (x 103 cells/ml) in the first lactation and 107.2 in later BCVA 2000 lactations; the incidence of clinical mastitis was recorded as 19.8%. A linear relationship was found between the production parameters of kg milk and kg protein and log10 (SCC). This equated to an individual milk yield loss of 1.29 kg/day for each unit increase in log10 (SCC) for cows in first lactation and 2.04 kg/day in older cows. The corresponding losses for milk protein were 0.042 and 0.067 kg/day respectively. These results yet again confirm that increases in SCC represent a direct loss of production as well as reducing the market value of milk. A review article published earlier this year discusses the problem of Streptococcus uberis mastitis (Leigh 1999), a subject all too familiar to many dairy practitioners! This interesting paper outlines the general progress made in mastitis control over recent years, discusses the pathogens involved and the economic and animal welfare implications, before focusing specifically on S. uberis. There then follows a more detailed description of the organism's identification, sources in the environment and pathogenesis as a cause of bovine mastitis. The paper concludes with a section on vaccine development against S. uberis mastitis. Vaccination would appear an attractive option for disease control against S. uberis mastitis. However, it is evident that much further research is required before we see effective vaccines available for use in UK herds. A paper on the efficacy of a biological response modifier (BRM) to prevent Staphylococcus aureus mastitis is of particular interest (Zecconi and others 1999). An interferon-α and interleukin-2 inducing BRM obtained from Parapox ovis is commercially available in some European countries. In this field trial the product was compared with a placebo in two dairy herds. The product was given 7 and 5 days before the expected date of calving and again within 24 h of calving. Milk samples were then taken 1, 7, 14, 21, 28 and 60 days after calving. This resulted in 1416 quarter samples from treated cows and 1128 quarter samples from placebo cows being examined bacteriologically. Some of the analysis performed failed to show significant results, and the results presented were often confusing. However, postpartum Staph. aureus intramammary infections had a frequency of 11.4% in the placebo group and 6.0% in the BRM group. The paper concludes that the use of this product significantly reduces the prevalence of Staph. aureus mastitis in the first 3 weeks postpartum. While this reviewer is still to be fully convinced of the efficacy of this product as a preventive treatment for Staph. aureus mastitis, the principle behind the use of immuno-modulating products is of interest. Further developments in this area may lead to novel therapeutics in the future. VOL 8 PART 2

CATTLE PRACTICE CONGENITAL JOINT LAXITY AND DISPROPORTIONATE DWARFISM A report of congenital joint laxity and dwarfism in calves on Prince Edward Island is the first from that area of Canada (Cebra and others 1999). The condition is similar or identical to the relatively common syndrome of congenital chondrodysrophy seen in spring born suckled calves in the UK and elsewhere. This recent paper while not reporting a definitive aetiological agent, once again implicates the feeding of poor quality silage to pregnant cattle as a possible risk factor. The simple advice to offer more than one forage, prevent the consumption of spoiled silage and ensure adequate mineral and trace element intakes, especially manganese, during the winter may help to prevent this syndrome. TOPICAL ISSUES FOR THE NEW MILLENNIUM The results of a Californian survey of dairy producer and industry leaders' opinions of on-farm Quality Assurance (QA) has recently been published (Payne and others 1999). Information was gained by the analysis of 413 mailed questionnaires and focus groups comprising 55 representatives of all sectors of the industry. It was acknowledged that chemical and microbial food safety, environmental health and animal welfare were issues that needed to be addressed. Reading this paper one gets a feeling of déjà vu, the content mirrors much of the discussion that has gone on in the UK over recent months. American producers considered that a marketadvantage in world trade would be desirable. Dairy Quality Assurance therefore has the potential to become a world trade issue; we must ensure that UK produce is amongst the best in the world if we are not to be barred from some markets for not complying with their QA requirements. The integrated control of parasites in conventional production systems and the rapidly expanding organic sector is something that we should all be taking an interest in. It is no longer satisfactory simply to recommend the latest anthelmintic to our clients. The subject of integrated biological control of parasites was reviewed at the recent International Conference of the World Association for the Advancement of Veterinary Parasitology (Thamsborg and others 1999). The paper acknowledges that at present the non-chemotherapeutic control of parasites in ruminants is based mainly on grazing management strategies and manipulation of stocking density. However, the future control of nematodes by larvaltrapping fungi, or parasite egg-destroying fungi is reported to look promising, if delivery systems can be developed. BCVA 2000 Quality Assurance Schemes and the increase in organic farming are just two of the many challenges facing our branch of the profession as we enter the new Millennium. Happy new year and good luck in 2000. ACKNOWLEDGEMENTS The author would like to thank UK Vet for permission to reproduce the Cattle News columns in Cattle Practice. REFERENCES Cebra C.K., Cebra M.L. & Ikede B.O. (1999) Congenital joint laxity and disproportionate dwarfism in a herd of beef cattle. J.A.V.M.A. 215: 519-521. Ellis J.A. (1998) Forgotten bovine viruses: A cause for clinical concern ? Vet. Med. 93: 765-768. Fourichon C., Seegers H., Bareille N. & Beaudeau F. (1999) Effects of disease on milk production in the dairy cow: a review. Prev. Vet. Med. 41: 1-35. Grøndahl-Nielsen C,. Simonsen H.B., Damkjer Lund J. & Hesselholt M. (1999) Behavioural, endocrine and cardiac responses in young calves undergoing dehorning without and with use of sedation and analgesia. The Vet. J. 158: 14-20. Koldeweij E., Emanuelson, U. & Janson L. (1999) Relation of milk production loss to milk somatic cell count. Acta Vet. Scan. 40: 47-56. Leigh J. (1999) Streptococcus uberis: A permanent barrier to the control of bovine mastitis? The Vet. J. 157: 225-238. McMeekan C., Stafford K.J., Mellor D.J., Bruce R.A., Ward R.N. & Gregory N. (1999) Effects of a local anaesthetic and a nonsteroidal anti-inflammatory analgesic on the behavioural responses of calves to dehorning. New Zeal. Vet. J. 47: 92-96. Munroe F.A., Dohoo I.R., McNab W.B. & Spangler L. (1999) Risk factors for the between-herd spread of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994. Prev. Vet. Med. 41:119-133. Nayar G.P.S., Hamel A.L., Lin L., Sachvie C., Grudeski E. & Spearman G. (1999) Evidence for circovirus in cattle with respiratory disease and from aborted bovine fetuses. Can. Vet. J. 40: 277-278. Paiba G.A., Wilesmith, J.W. & Evans S.J. (1999) Excretion of VTEC O157 by cattle. Vet. Rec. 144: 708. Payne M., Bruhn C.M., Reed, B., Scearce A. & O'Donnell J. (1999) On-farm Quality Assurance Programs: A survey of producer and industry opinions. J. Dairy Sci. 82: 2224-2230. Rodriguez R.O.L. & Rivera M.J. (1999) Fertility of beef cattle females with mating stimuli around insemination. Anim. Reprod. Sci. 54: 221-226. Rohrbach, B.W., Cannedy, A.L., Freeman, K.& Slenning, B.D. (1999) Risk factors for abomasal displacement in dairy cows. JAVMA 214: 1660-1663. Rukkwamsuk T., Kruip T.A.M. & Wensing, T. (1999) Relationship between overfeeding and overconditioning in the dry period and the problems of high producing dairy cows during the postparturient period. Vet. Quart. 21: 71-77. Shipka M.P. & Ellis L.C. (1999) Effects of bull exposure on postpartum ovarian activity of dairy cows. Anim. Reprod. Sci. 54: 237-244. Thamsborg S.M., Roepstorff A. & Larsen, M. (1999) Integrated and biological control of parasites in organic and conventional production systems. Vet. Para. 84: 169-186. Van Donkersgoed J., Graham T. & Gannon V. (1999) The prevalence of verotoxins, Escherichia coli O157:H7, and Salmonella in the feces and rumen of cattle at processing. Can. Vet. J. 40: 332-338. VOL 8 PART 2

CATTLE PRACTICE Whitney M.S., Roussel A.J. & Cole D.J. (1999a) Cytology in bovine practice: Solid tissue, pleural fluid, and peritoneal fluid specimens. Vet. Med. 94: 277-289. Whitney M.S., Roussel A.J. & Cole D.J. (1999b) Cytology in bovine practice: Synovial fluid, CSF, tracheal washes, and bronchioalveolar lavage specimens. Vet. Med. 94: 367-374. Zecconi A., Bronzo V., Casula A., Luzzago C., Moroni P., Piccinini R. & Spreafico G. (1999) Efficacy of a biological response modifier in preventing Staphylococcus aureus intramammary infections after calving. J. Dairy Sci. 82: 2101-2107. BCVA 2000 VOL 8 PART 2

CATTLE PRACTICE BCVA 2000 VOL 8 PART 1