Keeping Johne’s at bay

The co-op offers them help in managing the disease, including diagnostic testing and a comprehensive Johne's disease management guide developed by experts.

"We know Johne's disease can be a stressful and frustrating challenge for many dairy farmers," says LIC general manager biological systems Geoff Corbett.

"We want farmers to know there are tools available to help them manage the disease in their stock."

While there is no cure for Johne's disease in cattle, testing and managing it can help reduce cow losses and the longer-term health of a herd, Corbett says.

"We have had a lot of success in New Zealand with this approach. LIC has screened at least 100,000 animals a year with its Johne's disease diagnostic testing.... This supports farmers with a Johne's disease problem to identify and remove problem cows with advancing infection that are shedding the bacteria, before they develop clinical disease."

In recent years a joint venture including LIC and DairyNZ -- the Johne's Disease Research Consortium (JDRC) -- has developed disease management tools for farmers.

The consortium has funded a study by the animal health laboratory at LIC, and research into approaching Johne's disease from a genomics standpoint. This has included creating a testing regime -- available now to farmers -- which uses milk samples from the herd testing process run by LIC.

"This testing is popular with farmers, with the ease of being able to use the herd test milk sample. They need only schedule Johne's disease testing for the same time as herd testing and the LIC diagnostics laboratory does the rest. Vets follow up with results and help with ongoing management plans for the farmer," Corbett says.

While clinical Johne's disease mostly affects older animals, it is calves and young stock that are most susceptible to infection. With other management interventions, regular testing and culling can protect replacement heifers against Johne's disease and immediately reduce losses due to clinical Johne's disease among an adult herd.

If farmers screen and cull in autumn before calving they can minimise the number of cows dying from Johne's disease during and after calving -- a big benefit. It removes cows that will become clinical before they do so, and it protects the calves being born.

The JDRC developed a guide for farmers containing the latest and best advice on managing the disease. It is available from DairyNZ's website and has been distributed to many vets.

"Using the measures in the guide in conjunction with testing will help farmers reduce the impact of Johne's disease in their herd and bring it under control," Corbett says.

The guide tells how to recognise the disease, what causes it, how it is transmitted, which animals are most at risk and what to do about it. It includes the following:

Develop a practical long-term Johne's disease risk management plan with the help of your vet

Test the herd and cull high risk cows and heavy shedders before calving. This will reduce exposure of calves to Johne's bacteria at birth. Note that the stress of calving and milking will often push cows with advanced infection 'over the edge' to become clinically sick and die. Johne's testing herd-test milk sampling is a simple and efficient option to screen the milking herd

Limit calves' exposure to faecal matter, including keeping them out of effluent paddocks

Limit calves' exposure to adult cows because these pass on the disease (e.g. send your replacement heifers to a rearing unit with no adult cows or other adult ruminants as soon as possible after weaning)

Be vigilant when buying new stock to guard against introducing Johne's disease to your herd.

"The tests are useful in notifying high risk animals and 'super shedders' – these animals are high transmitters," Corbett says.

"The super shedders (cows with advanced Johne's disease) will excrete copious amounts of the bacteria into the environment; if they are pregnant, chances are their offspring will also be born with Johne's disease, thus continuing the cycle.

"Removing them reduces the transmission to other animals. The objective of the testing and management regime is to break the transmission cycle and infection of young stock.

"Successful management of Johne's disease won't be an overnight process, but vigilance with the principles in the management guide and appropriate testing will work."