Measuring antimicrobial use on dairy farms: A method comparison cohort study.

Antimicrobial use on UK dairy farms is measured for surveillance purposes, with veterinary sales data as a proxy for use. Two other methods of recording use have been used commonly on-farm: medicine waste bins and farm medicine records. However, none of these methods has been validated to measure antimicrobial use. The objective of this research was to assess agreement between the 3 most common methods for measuring on-farm antimicrobial use with a predetermined reference method on UK dairy farms. Antimicrobial use was measured prospectively on 26 UK dairy farms using medicine waste bins into which participants placed all discarded medicine packaging for a 12-mo period. At the end of 12 mo, farm medicine records and veterinary sales data were obtained retrospectively for participating farms. The reference method used was based on pre- and poststudy inventories combined with veterinary sales data. We investigated the systematic difference between the mean on-farm antimicrobial use measured by each of the 3 methods and a reference method, using one-way repeated-measures ANOVA models. Reliability and clinical relevance of the agreement between each pair of methods was quantified using the concordance correlation coefficient (CCC) and the Bland-Altman method, respectively. When compared with the reference method, veterinary sales data had excellent reliability for injectable antimicrobials and intramammary antimicrobials [95% confidence interval (CI) of CCC > 0.90] and moderate to excellent reliability for other antimicrobials (95% CI of CCC: 0.68-0.97). Medicine waste bins had good to excellent reliability for injectable (95% CI of CCC: 0.84-0.99), and intramammary products (95% CI of CCC: 0.78-0.94) and no agreement for other forms of antimicrobial. Farm medicine records did not agree for any form of antimicrobial when compared with the reference method. The use of veterinary sales data as a proxy for on-farm antimicrobial use in the UK represented excellent statistical reliability and offered clinically good agreement with the reference method when used to measure injectable antimicrobials. This study applies to the UK context and included a relatively small number of farms. However, these results have research and policy implications, both nationally and internationally, and are essential in accurately quantifying agricultural antimicrobial use to inform both animal and human health.

Randomised controlled trial to evaluate the effect of foot trimming before and after first calving on subsequent lameness episodes and productivity in dairy heifers.

The objective of this study was to assess both independent and combined effects of routine foot trimming of heifers at 3 weeks pre-calving and 100 days post calving on the first lactation lameness and lactation productivity. A total of 419 pre-calving dairy heifers were recruited from one heifer rearing operation over a 10-month period. Heifers were randomly allocated into one of four foot trimming regimens; pre-calving foot trim and post-calving lameness score (Group TL), pre-calving lameness score and post-calving foot trim (Group LT), pre-calving foot trim and post-calving foot trim (Group TT), and pre-calving lameness score and post-calving lameness score (Group LL, control group). All heifers were scored for lameness at 24 biweekly time points for 1 year following calving, and first lactation milk production data were collected. Following calving, 172/419 (41.1%) of heifers became lame during the study (period prevalence), with lameness prevalence at each time-point following calving ranging from 48/392 (12.2%) at 29-42 days post-calving to 4/379 (1.1%) between 295 and 383 days after calving. The effects of the four treatment groups were not significantly different from each other for overall lameness period prevalence, biweekly lameness point prevalence, time to first lameness event, type of foot lesion identified at dry off claw trimming, or the 4% fat corrected 305-day milk yield. However, increased odds lameness was significantly associated with a pre-calving trim alone (P = 0.044) compared to the reference group LL. The odds of heifer lameness were highest between 0 and 6 weeks post-partum, and heifer farm destination was significantly associated with lameness (OR 2.24), suggesting that even at high standard facilities, environment and management systems have more effect on heifer foot health than trimming.

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.

Epidermolysis bullosa in calves in the United Kingdom.

Epidermolysis bullosa (EB) was diagnosed in eight calves from four farms in the United Kingdom on the basis of clinical, histological and ultrastructural findings. In three affected herds, pedigree Simmental bulls had been mated with Simmental-cross cows. In a fourth herd two Holstein-Friesian calves were affected. Lesions included multifocal erosion and ulceration of the hard and soft palates, tongue, nares and gingiva, with onychomadesis (dysungulation). There was alopecia, erosion and crusting of the coronets, pasterns, fetlocks, carpi, hocks, flanks and axillae. Histopathological findings included segmental separation of full thickness epidermis from the dermis, with formation of large clefts containing eosinophilic fluid, extravasated red blood cells and small numbers of neutrophils. Follicular and interfollicular areas of skin were affected, with clefts extending around hair follicles and sometimes involving whole follicles. Ultrastructurally, there was evidence of vacuolar change within basal keratinocytes, corresponding to areas of histological clefting. Preliminary genetic screening of the candidate keratin genes (bKRT5 and bKRT14) has excluded mutations of these as the cause of this condition.

Renal dysplasia and nephrosclerosis in calves.

Renal dysplasia and nephrosclerosis in six calves, which were aged three to six months and from different farms in western Scotland and north-west England, was characterised clinically by stunted growth and renal failure with uraemia. Affected animals were depressed and one case exhibited severe neurological signs. Reduced erythrocyte counts were evident in three of four animals from which blood samples were submitted for haematology. At postmortem examination, the kidneys were bilaterally small, pale and firm, with marked fibrosis and sometimes contraction of the capsule. Histologically, affected calves had disorganised atrophic glomeruli, dilatation of tubules, loss of nephrons, areas of undifferentiated mesenchyme and diffuse interstitial and periglomerular fibrosis. There was minimal inflammation. Renal dysplasia and nephrosclerosis is a form of juvenile nephropathy of unknown aetiology that occurs sporadically in calves in the UK.

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.

Treatment of persistent intramammary infections with Streptococcus uberis in dairy cows.

A survey was conducted of the prevalence of environmental pathogens, especially Streptococcus uberis, as causes of clinical mastitis in dairy cows. The response of intramammary infections with S uberis to conventional treatment was monitored by taking milk samples for bacteriology and somatic cell counting seven, 14 and 21 days after the treatment. The results showed that 51 per cent of the infections failed to respond, and the odds of cases failing to respond was significantly increased when the individual quarter somatic cell count seven days after the treatment was greater than 201,000 cells/ml. Ninety-six per cent of the suspected S uberis isolates identified by culture were confirmed as S uberis by using the api 20 Strep system. Restriction endonuclease fingerprinting was used to type the strains of S uberis isolated from 75 milk samples from 32 cows. Analysis showed that 96 per cent of the cases of S uberis that failed to respond to conventional treatment were persistent infections with one strain rather than reinfections with different strains. The persistent cases of S uberis were treated further with an extended course of intramammary preparations containing either procaine penicillin with dihydrostreptomycin or cefquinome. There was no significant difference between the cure rates achieved by the two preparations, and 55 per cent of the cases that had failed to respond to conventional treatment responded to the additional treatment.

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.

Use of clinical information to predict the characteristics of bacteria isolated from clinical cases of bovine mastitis.

Farmers recorded the clinical signs of cows with clinical mastitis and submitted milk samples for bacteriological examination, so that the clinical signs could be correlated with the bacteriological findings. Odds ratios for the demeanour of the cow, the appearance of the milk, milk yield, udder texture, and the administration of parenteral antibiotics were calculated for mastitis cases classified in terms of their microbiology as either enterobacteriaceae, major Gram-positive pathogens, minor pathogens, 'no growths' or 'all other pathogens'. Animals infected with enterobacteriaceae had the highest odds of being reported as having a reduced milk yield, swollen or hard udders, watery milk and/or being systemically sick. A logistic regression model was used to predict the Gram-staining characteristics of the bacteria causing clinical mastitis. The clinical findings found to be significant predictors in the model were the demeanour of the cow and its milk yield. The regression model was used as a basis for a predictive test. Using a test data set, the sensitivity of the test was 28 per cent, its specificity was 96 per cent, the positive predictive value was 74 per cent and the negative predictive value was 80 per cent. The overall accuracy of these predictions was 79 per cent.

Dissecting aneurysm of the carotid artery as a cause of respiratory distress in adult cattle.

A two-and-a-half-year-old Friesian cow and a five-year-old Charolais cow developed severe respiratory distress and palpable swellings to the left of the larynx as a result of a dissecting aneurysm of the common carotid artery. Neither cow responded to medical treatment. The underlying pathogenesis of the condition was uncertain, but direct trauma to the carotid artery was a possible contributory factor. Aneurysms of the common carotid artery should be considered when swelling occurs in the region of the larynx or when respiratory distress is due to laryngeal compression.

Observations on ascites in nine cattle.

Signs of ascites were observed in only nine of 1863 cattle examined over a period of five years. The ascites was most commonly associated with either primary or secondary cardiac disease; cattle with ascites have a poor prognosis because the condition is usually assocaited with terminal disease. Two animals had cor pulmonale with chronic pneumonia, three had cardiomyopathy, one had bacterial endocarditis, two had thrombosis of the caudal vena cava and one had diffuse abdominal epithelioid mesothelioma.

Cost-effective antimicrobial drug selection for the management and control of respiratory disease in European cattle.

Respiratory disease in growing cattle has both animal welfare and economic implications, but the use of antimicrobial drugs to treat and control it is under public scrutiny owing to concerns that their use in food-producing animals may be detrimental to human health. This paper outlines criteria for the selection of appropriate and cost-effective drugs, based on good dinical practice and sound economic principles. It also suggests that these principles should be integrated into quality assurance schemes, and that the monitoring of antimicrobial resistance patterns among known bacterial respiratory pathogens should be improved.