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Cows

Foot passengers on a knife edge: is digital dermatitis being transmitted by hoof trimming equipment?

18 Jul, 14 | by Assistant Editor

 

Foot problems are one of the most serious welfare concerns facing the livestock industry today. In the UK cattle industry, digital dermatitis is a major cause of lameness and an increasingly serious problem. The disease can cause painful lesions on the skin around the hoof, as well as in other areas, including between the claws and on the udders of cows. It has also moved into sheep (known as contagious ovine digital dermatitis).

FIG1A

Mild digital dermatitis lesion on the bulb of a hind heel of a beef cow (from Sullivan and other 2013)

As well as negatively affecting animal welfare, digital dermatitis can adversely affect the productivity and profitability of farms. The National Animal Disease Information Service estimates that digital dermatitis costs, on average, £30 per cow per year in the UK. Affected cows produce less milk and have reduced fertility, and this accounts for the majority of economic losses due to the disease.

Clearly, digital dermatitis is a serious problem for the farming industry in the UK; it is therefore quite surprising that its epidemiology is not well understood.

 

FIG1B

A more severe  digital dermatitis lesion (Sullivan and other 2013)

A relatively new disease, the condition was identified for the first time in Italy in 1974 and wasn’t seen in the UK until the late 1980s. It is known to be caused by certain species of bacteria of the Treponema genus.

When it comes to treatment, footbathing and antibiotics have been shown to have limited effects, and as yet there is no definitive cure. Furthermore, relatively little is known about how the causal pathogens are transmitted between animals.

In a paper recently published in Veterinary Record, a group of researchers from the University of Liverpool (in collaboration with Roger Blowey from the Wood Veterinary Group) aimed to investigate a potential route of transmission for the disease – hoof trimming equipment.

Hoof/foot trimming is a standard element of livestock care. It is generally recommended that both cattle and sheep undergo a foot examination and, if necessary, have their feet trimmed at least once a year. The University of Liverpool team hypothesised that digital dermatitis-causing bacteria could be hitching a ride from animal to animal via the equipment used for hoof trimming, and designed and conducted a study to test this theory.

Six farms (two beef, two dairy and two sheep farms) in Denbighshire, Monmouthshire and Gloucestershire were included in the study. While on routine farm visits, vets were asked to randomly select animals undergoing hoof trimming and to take a sample from the hoof trimming equipment after it had been used. After the first sample was taken, the equipment was rinsed in iodine disinfectant and a second sample was taken.

‘We sampled equipment after it had been used to trim a hoof to determine whether treponemes could adhere to the knife following trimming’, said Leigh Sullivan, one of the authors of the paper. ‘Equipment was also sampled after the knife had been disinfected so we could assess whether disinfection removed treponeme DNA from the knife.’

The researchers found that treponeme DNA was present on 36 out of 37 hoof trimming instruments tested (97 per cent). They then sought to establish whether this DNA was from Treponema species that were known to cause digital dermatitis. Using PCR techniques, they found DNA of digital dermatitis-causing bacteria in the majority of cases after trimming a digital dermatitis-positive animal.

Following disinfection, the number of instruments with treponemal DNA detected was reduced to 13 of 37 (35 per cent).

‘The high detection rate of digital dermatitis treponemes on hoof trimming equipment was unexpected,’ said Dr Sullivan. ‘It appears that after trimming a symptomatic foot, treponemes are consistently able to adhere to the metal of the equipment. Additionally, in some cases, treponeme DNA was found on equipment used to trim asymptomatic animals, which could mean that treponemes were present on the foot due to another environmental factor or, although not obviously symptomatic at the time, the animal had an undetected early lesion.’

The authors of the paper conclude that the transmission of digital dermatitis-causing bacteria from animal to animal via hoof trimming equipment could be ‘significant and worrying’.  They also note that the routine disinfection method used was not always sufficient to remove all bacteria.

‘We understand from the data that this could be a contributing factor to the transmission of digital dermatitis,’ said Dr Sullivan. ‘However, other routes of transmission need to be explored to fully understand the spread of this disease.’

The authors note that this study does not prove that digital dermatitis is transmitted by foot trimming tools and that more research is needed. However, their results provide new information about the epidemiology of this important and pervasive condition.

 

New study investigates farmer attitudes towards the vaccination and culling of badgers

1 Aug, 13 | by Assistant Editor

 

Controversy persists in England over the best way to control the spread of bovine tuberculosis (TB). According to Defra, approximately 28,000 cattle were slaughtered in 2012 for purposes of TB control, and it may cost up to £1 billion to control the disease over the next decade.

Mycobacterium bovis may be transmitted from wildlife, including badgers, to cattle, and several schemes have been proposed that aim to curb the rate of these transmissions.

In 2012, the government announced a pilot badger cull in two areas in England. This gained large amounts of media attention and became a highly controversial topic, with outspoken arguments voiced both for and against culling.

A proposed alternative to culling is vaccination of a critical mass of badgers using a strain of the Bacillus Calmette-Guérin (BCG) vaccine, and this approach was adopted in 2011 by the National Trust (NT) on the Killerton Estate in Devon.

A paper recently published in Veterinary Record aimed to find out about attitudes towards badger vaccination among farmers on the Killerton Estate and, incidentally, to assess their views of other bovine TB control measures.

Of the 18 farm tenants on the 2000 ha estate, 14 agreed to take part in the study. All of the farmers included in the study owned cattle and all had been affected at some point by bovine TB. All participants were interviewed, and they were asked questions about their attitude towards TB control measures, the impact of TB, where they sourced information about TB and the ways that the NT had handled TB control. The interview transcripts were then analysed for recurring themes. The results are summarised below:

  • All respondents reported both significant financial and personal costs due to bovine TB, including additional workload, loss of milk sales, stress and worry.
  • Asked whether vaccination of badgers would be effective in controlling TB in cattle, two of the 14 participants said no, two were unsure and the remaining 10 were positive. However, many of the positive responses were conditional, for example, on how many badgers it would be possible to vaccinate. The authors note that the overall attitude towards vaccination was ‘one of tolerance, rather than optimism’.
  • Half of the farmers interviewed felt that there was a positive advantage to being involved in the NT’s vaccination scheme and only one thought that it may be a disadvantage. The majority of farmers were supportive of the NT’s decision to pursue the vaccination trial.
  • There was general agreement that the vaccination of cattle would be a good solution to the problem, but there was an awareness that a viable vaccine would take time to develop and that this would not be a feasible option for some time.
  • Half of the interviewees thought that culling badgers would be more effective than vaccination, two were against Defra’s culling proposals, and the other five gave no clear opinion.
  • Seven of the respondents cited gassing and destruction of badger sets as a more effective method of controlling TB than vaccination.

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The authors conclude that the study was conducted at a time when there was vigorous debate surrounding control of bovine TB and that the potential impact of this study upon policy will depend heavily upon how successful the Killerton vaccination trial is. There are two more vaccination phases in the trial in 2013 and 2014 and the farmers will be interviewed again after the final phase to assess whether their attitudes have changed.

The authors also note that the study highlights some important issues that may be relevant for the formulation of policy. First, the views of famers in the study tended to be more nuanced than the widespread media coverage has suggested, and while they were for bovine TB control in general, they were also willing to take into account the potential social and environmental impacts of control measures. Furthermore, the authors state that the attitude of the farmers toward vaccination is one of ‘resigned acceptance’ – they don’t believe that vaccination will be effective on its own, but they are glad that something is being done.  Finally, some respondents stated that they would prefer a combination of effective vaccination and culling programmes in order to reduce the population sufficiently that vaccination would be effective. 

Matt Lobley, one of the study authors, states:

“When the National Trust announced plans to undertake a badger vaccination experiment on its Killerton estate we were pleased to have the opportunity to undertake in-depth face-to-face interviews with the majority of the tenants. Bovine TB can have a debilitating impact on a farm and it has become such a highly politicised issue that opinions and options are often presented in a highly polarised manner. Talking to farmers under conditions of strict anonymity revealed a greater diversity of attitudes towards the control of bovine TB. Like farmers elsewhere, the Killerton tenants have been living with TB or the threat of TB for years and there was general appreciation that at least something was being done. On the other hand, expectations were low and there was a feeling that the badger population had been allowed to ‘get out of hand’, which meant some questioned the efficacy of vaccination alone. Even though our research was based on a small sample it is important that policymakers recognise that farmers attitudes are more nuanced than the public debate over TB often suggests.”

 

Team effort eradicates BVDV in Norway

31 May, 13 | by sarahbrown

Infection of cattle with pestiviruses can cause bovine viral diarrhoea (BVD) and, in some cases, mucosal disease. In pregnant animals, infection can also result in reproductive failure or persistently infected (PI) offspring. These PI animals produce and excrete the virus, usually at high concentrations, throughout their lives and are instrumental in the spread of infection, being the main reservoir of the virus. During the late 1980s, it became increasingly evident that BVD-related losses were economically significant to the livestock industry in Norway and that direct losses were estimated to be around 50 million Norwegian crowns (NOK) (£4.5 million).

A paper recently published in Veterinary Record by Torleiv Loken and Ola Nyberg describes a collaborative project that ran from December 1992 until 2004 with the intention of eradicating pestiviruses from the Norwegian cattle population.1 The collaborative project involved four key partners: the Norwegian Animal Health Authorities (NAH), the National Veterinary Institute, the cattle owners, and the cattle industry comprised of three farmers’ associations.

Loken and Krogsrud developed a strategy in 1992 based on the identification and culling of all PI animals2, and testing was performed in four tiers:

•                Tier 1 Annual screening for antibodies in bulk milk from all herds.

•                Tier 2 Herds found positive in tier 1 were examined for antibodies in pooled milk samples from primiparous cows.

•                Tier 3 Herds found positive in tier 2 were examined for antibodies in pooled blood samples from young stock. These herds were subject to restrictions.

•                Tier 4 Antibody-negative animals in herds that were found positive in tier 3 were tested for pestivirus antigen in blood and, if positive, were designated as a PI animal.

Following the culling of PI animals, a herd was considered to be free from pestivirus when pooled blood from youngstock was antibody negative on two sampling occasions, three months apart.

The number of herds with PI animals peaked at about 3000 in the second year of the project, and then decreased steadily. The last four PI cattle from the same herd were detected in 2005 and were immediately culled. Since then the surveillance programme has not detected any dairy cattle or beef animal positive for pestivirus. A cost benefit analysis estimated that the project has saved the Norwegian dairy industry losses of between 50 million to 200 million NOK annually (approximately £4.5 million to 18 million GBP). The total running cost of the project over 10 years was 52.4 million NOK. This, the authors say, clearly demonstrates that the project was economically highly beneficial. Subsequently, the value of close surveillance of the national cattle population has been emphasised to ensure that the cattle remain free from infection.

 

Persistently infected calf (1-year-old) with bovine viral diarrhoea virus

Persistently infected calf (1-year-old) with bovine viral diarrhoea virus

The authors conclude that the pestivirus eradication project was successful, resulting in the elimination of BVD and mucosal disease in the Norwegian cattle population and was economically highly beneficial.  Torleiv Loken praised the determination of the collaborators for the success of the project:

‘The story starts with the first demonstration of border disease in a lamb in Norway, which I published in 1981. The next year I diagnosed border disease in a liveborn kid, which was the first known diagnosis of border disease in a kid. That really tickled my interest and curiosity, and I went on to research pestivirus in cattle as well, which at the time was diagnosed very rarely in Norway. Along the line, the veterinarians and the cattle owners became very interested in pestivirus-related diseases and understood it could be very costly in a herd. The cattle owners pushed for more studies, and soon wanted – actually demanded – the eradication of this microbe. This willingness from the farmers to contribute to an eradication programme, both practically and economically, with strong support from the authorities, I think was one of the most important and basic keys to success.’

References

  1. Loken, T. & Nyberg, O. (2013) Eradication of BVDV in cattle: the Norwegian project. Veterinary Record doi: 10.1136/vr.101525
  2. Loken, T & Krogsrud J. (1992) Programme for making the Norwegian cattle free from pestivirus. Proceedings of the 2nd Symposium on Ruminant Pestiviruses. Annecy, European Society for Veterinary Virology. 1992. P66

The complexities of copper

23 Jan, 13 | by sarahbrown

 

Neville Suttle talks to Veterinary Record about copper supplementation in cattle feed.

COPPER  has a diverse range of biological roles in animals; there are many copper-dependent enzymes that are involved in energy metabolism, immunity, iron metabolism and coat pigmentation to name a few.  Neville Suttle, of the Moredun Foundation and co-author of a recent paper1 in Veterinary Record that followed a herd of cows with high winter mortality and high liver copper, explains: ‘In the UK, grass, hay and silage are widely but erroneously believed to be low in copper and complimentary feeds are often supplemented with the essential element. Without supplementation, forages will commonly contain 5 to 12 mg Cu/kg DM, cereals 4 to 6 mg Cu/kg DM and protein sources 10 to 40 mg Cu/kg DM.’

The level to which complimentary feeds should be supplemented with copper is the subject of much debate. The difficulty lies in estimating the available copper in a complete diet consisting of components differing widely in copper concentration and not knowing how they interact with each other. Copper toxicity is becoming more common in the UK because copper availability is often underestimated and requirements are overestimated. EU regulations set the maximum permitted level for copper in complete cattle feeds at 35 mg Cu/kg at 88 per cent dry matter. The Advisory Committee on Animal Feedstuffs (ACAF) suggests that under normal conditions, and in the absence of antagonists such as molybdenum and sulfur, which reduce copper availability, the maximum addition should be 20 mg Cu/kg dry matter.2

In the winter of 2005/06, 13 of 46 female calves in a herd died at less than one month old. They had developed chronic, low-grade diarrhoea and failed to thrive, despite good quality care. Samples that had been submitted to the Edinburgh Disease Surveillance Centre (EDSC) detected Cryptosporidium and coronavirus in two samples but this did not explain the high mortality. Three of the later casualties were submitted for postmortem examination, which revealed high copper concentrations in the liver. At this point, the lead investigator Archie Hunter from the EDSC, sought advice from Dr Suttle, who recommended that copper supplementation be reduced and surveillance continued. Three healthy culled newborn male calves were promptly submitted for postmortem examination to establish a baseline for liver histopathology.

Inspection of the feeds showed that mineral supplements were providing approximately 60 mg Cu/kg DM for milking cows and 41 or 46 mg Cu/kg DM for dry cows, both exceeding the maximum permitted level. Despite there being no typical clinical signs of chronic copper poisoning, supplementation was reduced to 45 mg Cu/kg in milking cows and later to 16 mg Cu/kg. For dry cows, the supplementation was reduced to 28 mg Cu/kg. Calf mortality fell the following winter (2006/07) but rose again the next (2007/08).  All supplements were withdrawn in 2008, including those in the milk substitute and creep feed, which had 10 and 35 mg Cu/kg added, respectively. Mortality once again dropped and stayed low for the following three winters, at which point the study ended.

Although many histological abnormalities were found in the livers of casualties, most were seen in equal abundance in the culled, healthy newborn calves, suggesting that chronic exposure of the unborn calf to high levels of copper caused changes in the livers of healthy calves. Other research has shown that depletion of liver copper can be exceedingly slow after the removal of copper supplements from mixed diets for lactating cows3; the results for culled newborn male calves in 2011 indicated that one cow still passed on high liver copper to her calves, five years after withdrawal of copper supplements began. If excess copper was still causing damage, where was it coming from? One possibility is that calf feeds were being continuously medicated with coccidiostat to control calf scours. The medication was killing off rumen protozoa, which normally keep copper availability suppressed by generating sulphide, a powerful copper antagonist; therefore, medicated calf feeds with no added copper could still provide too much copper.

Although association is not proof of causation, it seemed plausible that the reduction in copper supplements reduced calf mortality and liver disorders in young unweaned calves in this herd. The authors reasoned that the combination of high copper status and low-grade enteric infections were responsible for the history of liver disorder and calf mortality at birth.

As the extent of over-supplementing becomes more apparent in the UK, Dr Suttle commented: ‘I would like to see recommended rather than maximum permitted levels becoming the benchmark for copper supplementation and retrospective studies of calf mortality in previous outbreaks of copper poisoning, like the one reported recently  in dry Jersey cows.’ 4, 5 He also emphasises that requirements vary, depending on levels of molybdenum and sulfur in the environment, which quench copper availability: ‘Fixed rate supplementation to cover worst case scenarios is asking for trouble with a cumulative poison such as copper.’

 

 

References:

1. Hunter, A. G., Suttle, N., Martineau, H. M., Spence, M. A., Thomson, J. R., Macrae, A. I. & Brown, S. (2012) Mortality, hepatopathy and liver copper concentrations in artificially reared Jersey calves before and after reductions in copper supplementation. Veterinary Record doi: 10.1136/vr.10151

2. ACAF (2011) Guidance note for supplementing copper to bovines. www.food.gov.uk/multimedia/pdfs/committee/guidancesuppcopperbovines.pdf. Accessed January 23, 2013

3. Hittman, A. R., Grace, N. D. & Knowles, S. O. (2012) High and variable copper status identified among dairy herds in the Waikato region by concentrations of Cu in liver sourced from biopsies and cull cows. New Zealand Veterinary Journal 58, 130-136

4. Bidewell, C.A., Drew, J.R., Payne, J.H., Sayers, A.R., Higgins, R.J. &  Livesey, C.T. (2012) Case study of copper poisoning in a British dairy herd. Veterinary Record doi:1000267

5. Suttle, N. F.,  Martineau, H. M., Hunter, A. G., Thomas, J. R & Macrae, A. I. (2013) Atypical copper poisoning in Jersey dairy herds. Veterinary Record doi:10.1136/vr.f335

 

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