Disease-resilient deer on the market
PEEL FOREST ESTATE
15 January 2008
Disease-resilient deer on the market for the first time
Peel Forest Estate, a South Canterbury deer stud, is marketing stags from a programme designed to select resilience to Johnes, a wasting disease closely related to tuberculosis. This is thought to be a world-first for any species or breed of livestock.
Otago University immunologist Frank Griffin says the term resilient is chosen carefully. Unlike resistance, which is the ability to remain free from infection, resilience is the ability to stay healthy and productive following exposure to infection.
Johnes is widespread in dairy herds and sheep flocks around the world and is a problem in many New Zealand deer herds, where it can cause major losses in young stock. There is no effective treatment and control is normally by the culling of affected animals.
Professor Griffin, who has spent a life-time working on the management of Tb and Johnes disease in deer, says culling of susceptible animals and the selection of resilient bloodlines offers the best long-term prospects for the control of the disease.
“After Peel Forest diagnosed Johnes in 2000 the owner, Graham Carr, approached me. He had a number of valuable bloodlines that would be lost to the industry unless he could assure potential buyers that they were free from the disease.”
He says Peel Forest’s comprehensive pedigree database helped his group identify susceptible and resilient bloodlines, assisted by post-mortem data from culled animals.
“The stud had been involved in embryo transfer programmes and had eight extremely pure bloodlines, providing an opportunity for genetic study that I believe is unprecedented for domestic livestock. It has produced some of the most useful information I have seen in 40 years of research.”
The study found that resilience to the disease has a genetic basis and was linked to certain bloodlines. For example, a bloodline called B11 is extremely resilient and by chance is also associated with high breeding values for weight gain.
Frank Griffin believes resilient animals pose either no risk or a significantly lower risk for the spread of the disease. But he says he can’t be definitive, because he doesn’t have the proof, and this would be extremely costly and time-consuming to obtain.
Graham Carr sells all his stags as three year-olds, and while no test is perfect, they have had three annual blood-tests showing them to be free of the disease.
He says getting to this point has cost Peel Forest a small fortune in the culling of apparently healthy animals because they did not have the genetics for resilience, and the inability to sell stags and breeding hinds, the stud’s core business.
But, as with any farm that gets Johnes, the issue had to be confronted and a strategy adopted to get on top of it. Now, the point has been reached where he says Peel Forest can help other farmers who are trying to live with the disease in their herds.
“I can’t claim that we have reached the ultimate goal of breeding animals that are 100 per cent resilient, but we are well down the track. Farmers who have Johnes on their properties know they can get stags from us that will help,” he says.
“The stags will cope with exposure to the disease and their progeny will help build heritable resilience in their herd.”
Mr Carr says Peel Forest Estate was one of the first deer studs to adopt deer breeding values (DBVs) as a basis for the selection of highly productive animals and this remains very important. But having had exposure to Johnes, he is now treating resilience as being of equal importance.
“DBVs are important but whether they are breeding for finishing or replacements, farmers need high performance animals that are fit for their farming environment and unfortunately for many of them, that environment includes Johnes disease.”