Matt Ward, Beef + Lamb New Zealand’s General Manager North Island says the bacteria that causes Johne’s Disease (Mycobacterium avium Paratuberculosis) is widespread in this country and infects over 50% of all flocks and herds.
However, despite the bacteria being ubiquitous, the rate of clinical disease is very low.
In its clinical form, Johne’s Disease is chronic, progressive, contagious and generally fatal. It affects cattle, sheep, deer, goats and wildlife.
Between 2008 and 2010, the Johne’s Disease Research Consortium (a joint venture between science and industry) screened over 5000 dairy herds for Johne’s Disease through bulk vat milk ELISA tests. Only 1% of herds tested positive and 5% were classified as suspect for the disease.
While Matt says this is good news, Johne’s Disease has the potential to have a significant impact on animal welfare and market access.
It can also adversely affect individual farm businesses, as clinical Johne’s Disease reduces the productivity of dairy cattle both seasonally and across the lifetime of the cow. Modelling has shown the associated reduction in milk, protein and fat yields has the potential to reduce income on a dairy farm by 6-15%.
Matt explains that the Johne’s Disease Research Consortium ran between 2008-2016 and in that time, developed practical and cost-effective management tools and resources which could be used on-farm to reduce the prevalence of the disease.
After the Consortium finished, DairyNZ, Beef+ Lamb New Zealand and Deer Industry New Zealand joined forces to form the Johne’s Advisory Group (JAG). This working group has been charged with providing on-going support and insight for industry on research and development and the on-going control and management of Johne’s Disease.
Matt says JAG is a great example of sectors working collaboratively to control and manage a disease that could prove devastating to New Zealand’s red meat and dairy industries.
“While we are unable to eradicate Johne’s Disease, it is important we all work together to keep levels of clinical Johne’s Disease at a minimum to protect our businesses and our respective export industries."
In the dairy industry, bulk milk vat ELISA testing has been shown to be a useful tool for screening dairy herds for Johnes Disease, but should not be attempted in late lactation as raised antibody levels in milk interfere with the tests.
Research has shown that dairy cattle are most likely to test positive to Johne’s Disease between lactations three and six.
Matt says tests in young stock are notoriously unreliable, so there is little value in testing calves or heifers, rather management should be focused on minimizing their exposure to the disease from the environment or adult infected animals.
Young animals are the most susceptible to the disease and Jersey cows were shown to be three times more susceptible to Johne’s Disease than Holstein-Friesians.
For more information about the control and management of Johne’s Disease go to https://www.jdrc.co.nz/resources