Johne’s Disease is a major drain on the British cattle industry, leading to a range of health problems and sharply higher cull rates. But it is often a hidden problem, leaving many farmers fighting blind.
Fortunately, a new scheme in the south west is introducing a comprehensive programme to help farmers test their herds and draw up a strategy to tackle the disease. Funded by the European Rural Development Programme, the South West Healthy Livestock Initiative has secured £5m over two-and-a-half years to challenge a range of common health issues across the region, including Johne’s and Bovine Viral Diarrhoea in cattle.
Vet Debby Brown, from Castle Vets in Barnard Castle, recently visited the region to help roll out the project through local vet practices. The scheme offers 12 months’ support with diagnostic testing and two vet visits to draw up risk assessments and strategic planning on individual farms, with the benefit of 70% grant funding.
“At least 50% of the dairy herd is infected with Johne’s, and I would expect, if you looked deep enough, the beef side might even be higher,” she says. “The biggest losses are on units breeding their own replacements, as 80% of infections are picked up by calves in their first week of life.”
Johne’s lies dormant in cattle for the first three to seven years of life, but cannot be treated. In clinical cases it leads to infertility, scouring, loss of condition, lameness, and eventually death.
“It is quite immunosuppressive, so you also get higher incidence of other diseases,” says Mrs Brown. “It leads to much higher culling rates, so you need a far greater replacement rate.”
The bacteria – Mycobacterium paratuberculosis – are shed by infected cows, and are usually contracted by calves in the calving pen. “You only need one infected cow and the whole batch of calves could be infected; but they won’t show clinical signs for another three to seven years.”
The first stage of the project is to test a sample of 30 high-risk cows – those which are aged four to eight years old and are showing signs of infertility, poor condition or chronic lameness. Dairy cows are tested via their milk, while beef cattle are blood sampled. “If you have tested for TB, leave a gap of two months before testing for Johne’s, as the two tests cross-react,” says Mrs Brown.
“Unfortunately, cows won’t show the Johne’s antibody until they are very close to full clinical infection; so just because you get a negative result that doesn’t mean they are definitely not carriers.”
It is therefore essential to carry out the test in conjunction with a full risk assessment for the farm. Common sources of infection include purchasing cows from herds of unknown health status, spreading infected slurry onto youngstock pastures, and, in some cases, contact between calves and sheep or rabbits.
Within the herd, group calving pens, particularly where stocking rates are high and faeces is present, pose the greatest risk of transmission. Pooling colostrum and milk are also risk factors.
During the second farm visit, the vet will input risk data and test results to an online herd health management tool, My Healthy Herd, to help draw up a strategic action plan.
“If you know you have a Johne’s problem you would ideally keep high-risk and low-risk cows separate, calve in single pens, and not pool milk or colostrum. Keep calving areas as clean as possible, take calves off high-risk dams as soon as they are born, and calve outside if you can.”
Where a small number of cows test positive, producers should consider culling the whole line, as offspring will most likely be infected, she adds.
But when a large proportion of the herd is affected, alternative planning, regular testing, and careful group management will be necessary. “If you are lucky enough to be Johne’s free with a low-risk herd, you may also want a plan to keep it that way.”
• For more information contact the Rural Business School at Duchy College on 0845 4587485 or speak to your local vet.
• For more information on Johne’s disease and how to control it visit www.fwi.co.uk/johnescasestudy