November 2018

Research gets closer to identifying susceptible animals. ( Farm Journal Media )

Johne’s disease, also called mycobacterium avium subspecies paratuberculosis, results in inflammation and damage to the intestinal wall and negatively affects absorption of nutrients and overall cattle performance. The disease is present on dairies around the world, causing significant economic and animal welfare losses. A 2007 USDA study showed 68% of U.S. dairy herds have at least 8% of animals affected by the disease.

While a vaccine is available on a restricted basis to prevent Johne’s, no treatment is available for animals once the disease sets in. The disease can incubate inside the animal for several years, and when an animal shows clinical signs of Johne’s, it can quickly infect other animals causing widespread damage within the herd.

GENETIC RESISTANCE

A study at the University of Guelph, published in the November issue of the Journal of Dairy Science, studied opportunities to determine an animal’s genetic ability to resist the disease.

The study used milk ELISA scores on more than 168,000 Canadian Holsteins across 2,306 herds.

The study found important genomic regions on the Bos taurus autosome that showed significant association with Johne’s disease status. This includes two areas known to play key roles in the immune response of the potentially affected animal.

FUTURE OPPORTUNITY

The study identified the genetic structure of Johne’s disease in Canadian dairy cattle as measured by milk ELISA scores and identified genomic regions that could potentially influence the status of the disease. Researchers state the findings will be of significant value toward implementing genetic and genomic evaluations for future resistance to Johne’s disease.

Mike Opperman
Dairy Herd Management