Genetic marker test will help to eradicate Johne’s

Eradicating Johne’s disease from suckler herds could become much simpler from next year, with the launch of a genetic marker test for disease resistance.

Currently under development by Merial Ingenity, the test will enable farmers to select cattle based on their susceptibility to Johne’s, Merial’s David Bonsall told Farmers Weekly at Beef Expo, Carlisle.

“We’ve already found the quantitative trait loci and are now working on finding the marker related to that.

Trials are under way looking at the genetic make-up of both resistant and susceptible cattle to identify exactly which gene affects Johne’s resistance.”

Wiltshire-based cattle vet Keith Cutler believes the test could be particularly useful when selecting replacement breeding stock, both homebred and bought-in.

“Initially, it is likely the test will find use among pedigree herds, but in time it is likely commercial herds will come to use it, too.

Particularly when they have experienced an outbreak of Johne’s.”

Mr Cutler says the test could be used before replacements are chosen to give an extra insight into their suitability.

“Many herds select replacements purely on looks.

Adding a disease-resistance element to selection could make significant inroads into disease costs.

Many herds blood-test for BVD before selecting replacements, so taking a sample for genetic marker testing will mean little extra effort.”

He believes farmers buying replacements from dairy herds will also benefit from the test because it will enable them to learn more about the animals before they buy them. “Testing animals for Johne’s resistance could become a useful marketing tool. Bull breeders and AI companies could also benefit by being able to market bulls and semen as Johne’s resistant, too.”
Dairy farmers are also likely to benefit by being able to select AI bulls on the basis of disease resistance. “Currently, many herds pre-select their replacements on the basis of cow choice, choosing only a set number of cows to put to dairy sires. Adding this test to the mix will mean breeding cow selection can be even more meaningful.”
In addition to the Johne’s marker test, Mr Bonsall said Merial would look to launch other new tests in the Ingenity range soon. “We are also working on identifying cattle for fertility, docility and temperament and will be increasing the range of carcass trait tests offered.”
Quizzed on the economics of using the marker tests, he said the main benefits would come not from improved sale prices, but through increased on-farm efficiency and productivity. “Reducing the number of barren cows or having cows which are more docile and easily managed will cut management costs.”
On the carcass trait markers, he said tests would be able to identify cattle capable of breeding offspring with increased rib eye size, larger loins and improved marbling. “The aim, as always, is to increase the number of cattle meeting mainstream market selection.”
It may also be possible with future markers to identify cattle with improved fatty acid balance in their meat and, as such, produce healthier meat. “We might even get to the stage of marketing steak as being ‘Heart Healthy’,” he added.
jonathan.long@rbi.co.uk