David C Barrett

Clinicopathological presentation of cardiac disease in cattle and its impact on decision making

The records of 116 cattle suffering from cardiac disease were examined retrospectively. On the basis of the results of postmortem examinations there were 52 cases of endocarditis, 39 of pericarditis and 25 congenital cardiac defects. The most useful clinical tool for differentiating between these conditions was auscultation of the heart. The cases of pericarditis were characterised by muffled heart sounds, and the cases of endocarditis and congenital cardiac defects were characterised by a cardiac murmur. Endocarditis could be differentiated from congenital cardiac defects by the presence of a jugular pulse, venous distension, oedema, a reduced appetite, pain and polyarthritis, whereas congenital defects were associated with conformational abnormalities. These two conditions could also be differentiated by differences in the plasma sodium concentration, the albumin:globulin ratio, red blood cell count, lymphocyte count and haematocrit. The ability to differentiate between these three groups of cardiac diseases can help the veterinary practitioner in deciding whether treatment, economic salvage (slaughter for human consumption) or disposal (slaughter not for human consumption) is likely to be the best option.

Clinical and pathological features of dilated cardiomyopathy in Holstein-Friesian cattle.

Dilated cardiomyopathy is a primary disease of the heart muscle that has been reported in Holstein-Friesian cattle worldwide in the past 20 years. Nine cases of the condition were compared in terms of their clinical and pathological characteristics with nine unaffected animals matched for age, sex and breed. Their clinical signs included right-sided heart failure with severe subcutaneous oedema, ascites and/or hydrothorax and distended jugular veins. There were no characteristic biochemical or haematological changes. Postmortem, the affected hearts were enlarged with all the chambers dilated and walls of variable thickness. In most cases the kidneys were pale with a pitted surface. Histologically there was marked perimysial and endomysial fibrosis, extensive loss of cardiomyocytes by coagulative or colliquative necrosis, increased variation in the cross-sectional area of the myocardial fibres, and multifocal disarray and vacuolation of myocytes. Scanning electron microscopy showed that in all cases there was a mild myocardial inflammatory infiltrate, either diffuse or multifocal, which was identified by immunohistochemical labelling as T cells.

Clinical recognition and treatment of bovine cutaneous actinobacillosis

Although the immune system is capable of mounting a response against many cancers, that response is insufficient for tumor eradication in most patients due to factors in the tumor microenvironment that defeat tumor immunity. We previously identified the immune-suppressive molecule CD200 as up-regulated on primary B cell chronic lymphocytic leukemia (B-CLL) cells and demonstrated negative immune regulation by B-CLL and other tumor cells overexpressing CD200 in vitro. In this study we developed a novel animal model that incorporates human immune cells and human tumor cells to address the effects of CD200 overexpression on tumor cells in vivo and to assess the effect of targeting Abs in the presence of human immune cells. Although human mononuclear cells prevented tumor growth when tumor cells did not express CD200, tumor-expressed CD200 inhibited the ability of lymphocytes to eradicate tumor cells. Anti-CD200 Ab administration to mice bearing CD200-expressing tumors resulted in nearly complete tumor growth inhibition even in the context of established receptor-ligand interactions. Evaluation of an anti-CD200 Ab with abrogated effector function provided evidence that blocking of the receptor-ligand interaction was sufficient for control of CD200-mediated immune modulation and tumor growth inhibition in this model. Our data indicate that CD200 expression by tumor cells suppresses antitumor responses and suggest that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing cancers.

Antibiotic dry cow therapy: where next?

RESPONSIBLE use of antibiotics and concerns surrounding antimicrobial resistance (AMR) are pervading all areas of both veterinary and human medicine. It is the prescribing clinicians responsibility to ensure that the use of antimicrobials is justified in all situations. Increasingly, the assurances justifying the prescription and use of antibiotics are under scrutiny and may in the future be subject to challenge on a number of fronts. The routine use of antibiotics at drying off in dairy cows is one such area of reappraisal and challenge. In order to validate and uphold the principles of responsible use of antimicrobials, analysis of past prescribing practices and outcomes must be combined with robust clinical research evidence. Even a cursory analysis of on-farm and within-practice data has the potential to influence future prescribing; challenging and reappraising the necessity for antibiotic prescribing in certain clinical situations has been known to lead to a marked reduction in antibiotic use. When critically appraising the current approach to drying off dairy cows, it is worth looking not only at current and future drivers for change but also at how we got to where we are today. Many factors have influenced the approach to managing dairy cows at the end of lactation: the social environment (attitudes to antibiotic use), pharmacological environment (products available) and physical environment that cows occupy have all seen significant change. Antibiotic dry cow therapy (aDCT) was introduced in the 1950s as part of a structured mastitis control plan (Five-Point Mastitis Control Plan) developed at the National Institute for Research in Dairying at the University of Reading. Slow release antibiotic preparations infused into each quarter of a cow at drying off not only improved the chance of elimination of existing intramammary infections (IMI) but also afforded the cow some protection from new IMI during …

A telephone-based case-control study of fatal equine colics in Wales during 1988 with particular reference to grass disease

Abstract The present study was designed to evaluate a telephone survey in collecting epidemiological information. Of particular interest was the possible association between grass disease and scrapie. We have carried out a case-control study of fatal equine colic cases seen by veterinary practitioners in Wales in 1988, looking at the exposure of these cases to scrapie-infected sheep. The results indicate that this type of survey is of value where the information required is limited and where recall is likely to be good. The response rate was 95% and the material cost was comparable with that of a postal survey. A total of 1331 cases of colic were reported and 93 (7%) of these were fatal. Seventeen cases of grass disease (1.3%) were reported, but only 41% were confirmed histologically. Scrapie was reported on only two of the premises where fatal colics occurred. There was no association with grass disease at the 5% level, but in view of the fact that the results approached significance (P=0.06), we suggest that this hypothesis warrants further investigation.

Participatory Policy Making by Dairy Producers to Reduce Anti-Microbial use on Farms

Pressures for more responsible use of anti‐microbial (AM) medicines in food animals are likely to increase from policymakers and the food industry, including retailers. To address this challenge, participatory approaches to welfare interventions and disease prevention may also be necessary alongside more conventional regulatory measures. This article describes the process of enabling groups of dairy producers to use a participatory policy making approach to develop an AM stewardship policy. The policy includes measures agreed to by all producers for more responsible use of AMs, whilst maintaining or improving dairy herd health and welfare. This process provided a unique opportunity for collaboration and dialogue between producers, veterinarians, industry and researchers. Its participatory nature encouraged comprehensive learning for all involved. This integration of science with producers’ knowledge and experience led to credible and practical recommendations designed to deliver real and lasting change in AM use. The multidisciplinary nature of this research marks a significant contribution to embedding social science skills and approaches into the veterinary sphere. As an initial step in creating better understanding of how participatory approaches with farmers can be applied in a UK context and more widely, this work serves as a pilot for promoting more responsible use of veterinary medicines in other livestock species.

Antimicrobial use in food-producing animals: a rapid evidence assessment of stakeholder practices and beliefs

Food-producing animals throughout the world are likely to be exposed to antimicrobial (AM) treatment. The crossover in AM use between human and veterinary medicine raises concerns that antimicrobial resistance (AMR) may spread from food-producing animals to humans, driving the need for further understanding of how AMs are used in livestock practice as well as stakeholder beliefs relating to their use. A rapid evidence assessment (REA) was used to collate research on AM use published in peer-reviewed journals between 2000 and 2016. Forty-eight papers were identified and reviewed. The summary of findings highlights a number of issues regarding current knowledge of the use of AMs in food-producing animals and explores the attitudes of interested parties regarding the reduction of AM use in livestock. Variation between and within countries, production types and individual farms demonstrates the complexity of the challenge involved in monitoring and regulating AM use in animal agriculture. Many factors that could influence the prevalence of AMR in livestock are of concern across all sections of the livestock industry. This REA highlights the potential role of farmers and veterinarians and of other advisors, public pressure and legislation to influence change in the use of AMs in livestock.

Measuring the growth rate of UK dairy heifers to improve future productivity

Sub-optimal heifer growth is associated with higher disease rates and reduced future performance and longevity in the dairy herd. This report describes a system for measuring heifer growth from birth to first calving that was used on commercial dairy farms in South West England, in order to gather benchmarking data to feed back to farmers. Weights (n = 8443) were collected from 20 farms. There was a marked variation in individual and herd mean growth rates. Overall, calves gained no weight in the first 8 days after birth and had a very low growth rate (median 0.12 kg/day) up to 30 days, a period when feed conversion efficiency is high and calves are vulnerable to disease. Heifers whose growth rate up to 180 days was low were significantly less likely to achieve target service weight (374 kg) by 420 days. Monitoring heifer growth during the rearing period enables farmers to improve heifer growth rates and so impact both the efficiency of heifer rearing and, potentially, the productivity and performance of the adult herd.

Bovine spinal anomaly with anatomical similarities to complex vertebral malformation

improve its feed intake, and it subsequently responded by eating some gruel from a bucket. After a second course of stomach tube feeding for a few days during the fifth week after surgery, the pony started to eat gruel more readily. Thirty-eight days after surgery its bodyweight had increased to 260 kg (estimated by weight tape) and, 50 days later, the pony reached its normal weight of 313 kg. It would eat a normal ration as long as the food was wet, and would graze in a field, but mastication and swallowing were not normal and the animal was slow in finishing meals and in chewing grass when grazing. After four months, the pony was grazing and masticating normally and no longer required wet or dampened food. The owner believed the pony was slower at finishing its feed because, when kept overnight in a shed with other horses and fed hay, it appeared to lose weight. By keeping the pony in a stable on its own, its allocation of hay was gone by the morning and normal weight was maintained. Six months after the onset of signs, the pony appeared to have fully recovered. Early in the following three-and-a-half years, it had one possible mild bout of abdominal discomfort which had resolved before veterinary examination could be undertaken and which normally would not have prompted the owner to seek veterinary attention. The pony continued to be in full work, and four years after the onset of chronic grass sickness appeared normal. The histological features of autonomic neuronal degeneration (chromatolysis, pyknosis) can be recognised easily, but assessment of neuronal loss depends on examination of sufficient intestinal tissue to be confident that neurons really are absent. Casual examination of single small sections of intestinal biopsy may give a spurious impression of neuronal loss because of the dispersed distribution of the neuronal network. Thus, in this case, the interpretation of extensive neuronal loss in the ileum can be relied on confidently, because nine blocks of the biopsy were examined. The difficulty in recognising autonomic neuronal loss is compounded by the fact that there appears to be little or no inflammatory or reactive response to the loss of nerve cells at this site. Cisapride has been advocated for use as a prokinetic agent in chronic grass sickness cases to improve intestinal motility and assist recovery (Doxey and others 1995b, Milne and others 1996). It was not used in the present case, partly for economic reasons but also because a confirmed case of chronic grass sickness, with no evidence of autonomic ganglionopathy in an ileal biopsy during early clinical signs of the disease (Rh. ap Rh. Owen, D. F. Kelly, unpublished observations), indicated that the need for such a drug in some cases of chronic grass sickness may be unnecessary. Two possibilities have been suggested to explain why some horses may recover from this disease: either functional adaptation of surviving neurons or neuronal regeneration (Doxey and others 1998). Since neuronal injury occurs in most cases of grass sickness and as neuronal regeneration is not known to occur, the former possibility is the more plausible basis for functional recovery of the affected bowel.

Ceasing the use of the highest priority critically important antimicrobials does not adversely affect production, health or welfare parameters in dairy cows

Due to scientific, public and political concern regarding antimicrobial resistance (AMR), several EU countries have already taken steps to reduce antimicrobial (AM) usage in production animal medicine, particularly that of the highest priority critically important AMs (HP-CIAs). While veterinarians are aware of issues surrounding AMR, potential barriers to change such as concerns of reduced animal health, welfare or production may inhibit progress towards more responsible AM prescribing. Farmers from seven dairy farms in South West England engaged in changing AM use through an active process of education and herd health planning meetings. Prescribing data were collected from veterinary sales records; production and health data were accessed via milk recording and farm-recorded data. This study demonstrates that cattle health and welfare—as measured by production parameters, fertility, udder health and mobility data and culling rates—can be maintained and even improved alongside a complete cessation in the use of HP-CIAs as well as an overall reduction of AM use on dairy farms. This study also identified a need to consider different metrics when analysing AM use data, including dose-based metrics as well as those of total quantities to allow better representation of the direction and magnitude of changes in AM use.