K. Ellis

Dairy cow cleanliness and milk quality on organic and conventional farms in the UK

A subjective cow cleanliness scoring system was validated and used to assess the cleanliness score of dairy cows at different times in the year. A longitudinal study followed a number of farms from summer to winter, and a larger, cross-sectional study assessed a greater number of farms during the housed winter period. The scoring system was demonstrated to be both a repeatable and practical technique to use on-farm and showed that cows become dirtier in the transition from summer grazing to winter housing. Although farming system (organic or conventional) had no effect on cow cleanliness when cows were at grass, when housed in the winter, organic cows were significantly more likely to be cleaner. There was a link between cow cleanliness scores and milk quality, with herds having lower bulk tank somatic cell counts (BTSCC) tending to have a lower (cleaner) median cow cleanliness score; with this relationship strongest for the organic herds. There was no significant link between cleanliness score and Bactoscan (BS) count or clinical mastitis incidence. No major mastitis pathogens were cultured from bulk tank milk samples from the quartile of herds with the cleanest cows in contrast to the quartile of herds with the dirtiest cows, where significant mastitis pathogens were cultured. Based on this study, all farms, especially organic systems, should attempt to keep cows clean as part of subclinical mastitis control.

Investigation of the vitamins A and E and beta-carotene content in milk from UK organic and conventional dairy farms.

During a 12-month longitudinal study, bulk-tank milk was collected from organic (n=17) and conventional (n=19) dairy farms in the UK. Milk samples were analysed for vitamin A (retinol), vitamin E (alpha-tocopherol) and beta-carotene content. The farming system type, herd production level and nutritional factors affecting the milk fat vitamin content were investigated by use of mixed model analyses. Conventionally produced milk fat had a higher mean content of vitamin A than organically produced milk fat, although there were no significant differences in the vitamin E or beta-carotene contents between the two types of milk fat. Apart from farming system, other key factors that affected milk fat vitamin content were season, herd yield and concentrate feeding level. Milk vitamin content increased in the summer months and in association with increased concentrate feeding, whilst higher-yielding herds had a lower milk vitamin E and beta-carotene content. Thus, conventional dairy farms in the UK produced milk with a higher vitamin A content, possibly owing to increased vitamin A supplementation in concentrate feeds. However, knowledge of the effects of season, access to fresh grazing or specific silage types and herd production level may also be used by all producers and processors to enhance the vitamin content in milk.

Diagnosis of intramammary infection in samples yielding negative results or minor pathogens in conventional bacterial culturing

Up to half of quarter milk samples submitted for mastitis diagnosis are culture-negative results or lead to identification of coagulase-negative staphylococci or Corynebacterium bovis in conventional culturing, the so-called minor pathogens. The interpretation and usefulness of these results in terms of udder and animal health management is limited, even though the amount of resources spent is relatively high. This work aimed to test two methods of analysis of milk samples with the goal of increasing detection of intramammary pathogens. In the first study, 783 milk samples were processed in duplicate: before and after freezing at -20°C for 24 h, using standard bacteriological techniques. There was a significant difference between the two methods with samples frozen for 24 h yielding significantly fewer Gram-positive catalase-positive cocci, Gram-negative bacilli, Gram-positive bacilli and significantly more samples leading to no growth, than samples before freezing. The number of samples yielding Gram-positive catalase-negative cocci was not significantly affected by freezing. In the second study, a real-time PCR-based test was performed on milk samples with an individual quarter somatic cell count above 500,000 cells/ml that were either negative (n=51 samples) or that led to the isolation of minor pathogens in culturing: Corynebacterium bovis (n=79 samples) or non-aureus staphylococci (NAS, n=32). A mastitis pathogen, beyond the result obtained with standard bacteriology, was detected on 47% of the no-growth samples, on 35% of the samples from which C. bovis had been isolated and on 25% of the samples from which NAS had been isolated. The most commonly detected major pathogen was Escherichia coli, followed by Streptococcus uberis, Arcanobacterium pyogenes/Peptoniphilus indolicus and Streptococcus dysgalactiae. These results suggest that simply freezing milk samples for 24 h does not increase the detection of intramammary bacteria in milk samples and therefore should not be recommended. However, use of the real-time PCR-based test may be useful in diagnosing intramammary infections when milk samples with high somatic cell counts are culture-negative or when culturing results in the detection of minor pathogens.

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.

Production impact of a targeted selective treatment system based on liveweight gain in a commercial flock

The sustainability of sheep production is hindered by anthelmintic resistance. Options to slow down or prevent resistance have been widely studied but their application in the field is still limited. In this study, the practical application and effect of a targeted selective treatment (TST) approach for the treatment of parasitic gastroenteritis was investigated in lambs (n = 385) over a 2 year period. At 14-day intervals during the grazing season, liveweight, breech soiling and anthelmintic treatments were individually recorded. Selection of lambs for anthelmintic treatment in the TST group was based on pre-calculated individual growth rates, with a matched cohort routinely treated (RT) with anthelmintic drug every 6 weeks. The adoption of a TST approach had no negative effect on the liveweight gains of the lambs, time to finishing or breech soiling measures compared to RT lambs; however a 50% decrease in anthelmintic treatment was observed in the TST group. The time to implement this system averaged 2 min per lamb. It is concluded that the TST could be suitable for commercial sheep farms, in association with automated weighing systems, potentially reducing selection for anthelmintic resistance, while having no negative effect on production.

Eradication programme for bovine viral diarrhoea virus in Orkney 2001 to 2008

The strategies used and the results obtained in Orkneys bovine viral diarrhoea virus (BVDV) eradication programme over eight years (2001 to 2008) are presented and discussed. The venture was undertaken by local veterinary practices and the Orkney Livestock Association (OLA) with the financial support of the Orkney Islands Council. Participation is voluntary; the programme comprises screening of youngstock, a whole-herd test if required, elimination of persistently infected animals and strict biosecurity measures and/or vaccination. BVDV-free herds are certified, and certification is updated annually by retesting the youngstock. The programme aims to minimise economic losses, thereby increasing the competitiveness of the Orcadian cattle industry and to improve animal health and welfare by eliminating virus circulation. Information from databases of the Scottish Agricultural College, Biobest Laboratories and OLA show that despite a significant reduction in the overall prevalence of BVDV on Orkney during the initial stages of the eradication programme, there has been little progress made since 2006 and that some difficulties have been encountered, with herd BVDV breakdowns following initial eradication. These results highlight the need for continued motivation of farmers, strict application of biosecurity measures and/or systematic vaccination of all seronegative breeding animals.

Use of diagnostic markers to monitor fasciolosis and gastrointestinal nematodes on an organic dairy farm

A 12-month study was conducted to assess and monitor gastrointestinal tract nematodes and liver fluke in cohorts of cattle on a Scottish organic dairy farm. Various diagnostic markers for helminth parasites of cattle from different age groups were assessed monthly from April 2007 to March 2008. First season grazing stock were subjected to significant challenge from Ostertagia ostertagi nematodes as reflected in serum pepsinogen concentrations, which rose markedly in the second half of the grazing season. In addition, plasma albumin concentrations decreased and faecal egg counts (FEC) increased moderately, indicating exposure to both O ostertagi and probably Cooperia oncophora. Second season grazing animals had a peak FEC early in the grazing period, suggestive of a potential carry-over of Ostertagia species infection (‘Type 2’) during housing. All classes of cattle showed evidence of fluke (Fasciola hepatica) infection. Adult cow exposure to O ostertagi and fluke was estimated via the use of ELISA testing to detect antibodies to O ostertagi and F hepatica and the high levels detected suggested a significant exposure response. Despite low stocking densities and sympathetic grazing management, there was a significant challenge to all grazing stock from gastrointestinal nematodes and liver fluke.

Clinical differentiation of malignant catarrhal fever, mucosal disease and bluetongue.

THE 2006/07 outbreak of bluetongue virus infection in northern Europe has been characterised by a higher proportion of cattle showing clinical signs (Thiry and others 2006, Guyot and others 2007). This is not often associated with outbreaks of the disease as it is more usual for cattle to be asymptomatic. Adult cattle have mainly been affected, showing ulcerative and necrotic lesions on the muzzle and in the oral cavity, conjunctivitis, lacrimation and periocular dermatitis, photosensitivity-type skin lesions around the midline (later in the course of disease), a drop in milk yield, mild pyrexia and transient loss of body condition, ulcerative and necrotic skin lesions on the udder, teats and vulva, and oedema of the distal limbs (Guyot and others 2007). Bluetongue was first reported in the UK in September 2007, and there is a real threat of the disease affecting more animals in the country, both from infected midges in the UK and those arriving from continental Europe in wind currents (Gloster and others 2007). This, alongside foot-and-mouth disease (FMD), has led to severe economic consequences in terms of both animal movement restrictions and the export market, and animal welfare. Among the differential diagnoses for bluetongue are malignant catarrhal fever (MCF) and mucosal disease, which are endemic to the UK. The clinical differentiation of these three conditions is therefore highly relevant. The aim of this study was to characterise the clinical findings typical of cases of MCF and mucosal disease, and to compare these with clinical findings characteristic of the recent bluetongue outbreak in northern Europe, to assess their value in differentiating these three conditions. Thirty-eight cases of bluetongue were selected from the database of records of the ambulatory clinic of the Faculty of Veterinary Medicine, University of Liège, from August 2006 to February 2007. The criteria for inclusion were a clinical diagnosis of bluetongue and a positive test result either for detection of antibody by a competitive ELISA or detection of viral nucleic acid by real-time reverse transcriptase-PCR, as described by Toussaint and others (2007). Sixty-six cases of mucosal disease and 11 cases of MCF were selected from the database of records of cattle admitted to the University of Glasgow Veterinary School (UGVS) from January 1989 to June 2007. Cases of mucosal disease were included on the basis of typical pathological changes at postmortem examination and on being antigen-positive (HerdChek BVDV Antigen; Idexx) and antibody negative (Svanovir BVDV-Ab; Svanova) for bovine viral diarrhoea virus (BVDV) by ELISA. Cases of MCF were included on the basis of postmortem examination findings and on being positive for antibody to ovine herpesvirus type 2 (OvHV-2) by an immunofluorescent antibody test (Reid 2004) or for OvHV-2 nucleic acid by PCR (Hussy and others 2001). All cases diagnosed as MCF were antigen-negative for BVDV. All the animals had been subjected to a thorough clinical examination according to standard protocols, albeit with slight differences between the two institutions. Cases of bluetongue were examined on-farm in Belgium, whereas cases of MCF and cases of mucosal disease were examined after being referred to the UGVS clinic. Case data were summarised to determine the most common presenting signs for each disease. A Freeman-Halton extension of Fisher’s exact probability test was performed (VassarStats 2007) to test for significant differences in the frequency of clinical signs between the three conditions (Freeman and Halton Veterinary Record (2007) 161, 858-859

A case report of Mycoplasma wenyonii associated immune-mediated haemolytic anaemia in a dairy cow.

Background and case presentationA three year old, second lactation Holstein dairy cow presented to the Scottish Centre for Production Animal Health and Food Safety, Glasgow University Veterinary School in November 2014 with a history of post-calving vulval/vaginal bleeding nine days prior to presentation, followed by a sudden reduction in milk yield. Subsequent investigations resulted in a diagnosis of immune-mediated haemolytic anaemia secondary to infection with Mycoplasma wenyonii. ConclusionThis report of a novel presentation of Mycoplasma wenyonii in a dairy cow illustrates the need to consider M.wenyonii as a potential differential diagnosis when a cow presents with anaemia and will discuss the potential implications of the condition at herd-level.

Looking for the unusual suspects: a Salmonella Dublin outbreak investigation

Salmonella enterica serovar Dublin (S. Dublin) is primarily a pathogen of cattle, although it can be zoonotic and cause life-threatening disease in susceptible individuals. Human infection can occur through contact with livestock, although most outbreaks are foodborne. Most of the reported cases in Scotland occurred following the consumption of contaminated raw milk, until the sale of unpasteurized milk was banned in 1983. Recent data show that most human S. Dublin outbreaks reported in Scotland occurred in the south-west area, with clustering of human outbreaks with cattle populations, especially with dairy herds. This report details a clinical S. Dublin outbreak in a dairy farm which resulted in zoonotic spread, and raises awareness on companion animals as potential reservoirs of disease which should not be overlooked in a farm setting. In August 2006, a 70-cow closed dairy herd with no previous history of clinical salmonellosis reported an abortion in an adult British Friesian cow