Johne's disease (JD) continues to be a major threat to both the beef and dairy industry. Johne's is a bacterial infection of the intestinal tract that can result in significant livestock losses. The Michigan State University (MSU) JD control demonstration project is part of a national program with the aim of demonstrating successful disease control strategies.
One of the herds enrolled in the Michigan project is a commercial cow-calf operation that began experiencing significant problems with JD five years ago. The owner identified several cows soon after calving that developed classical signs of JD - chronic diarrhea and weight loss that failed to respond to treatment. The problem came to a head two years ago when nearly 25% of the 1st calf heifers were affected and eventually died or were culled. Last December a JD risk assessment was conducted and a disease control program was developed. Approximately 7% of cattle greater than 2 years of age were infected with JD.
MSU's Dan Grooms, DVM, Ph.D., says JD is spread from infected adult animals to younger animals. The primary source of transmission is feces, colostrum and milk. In-utero transmission can also occur. Several farm management issues that significantly increased the risk of disease transmission are:
- Concentrated common calving area that became heavily contaminated with feces during the calving season.
- Cow-calf pairs remained in the calving area for up to two weeks, increasing the risk of being exposed to feces containing JD.
- Legs and udders of cows heavily contaminated with feces at the time of calving, increasing the likelihood of ingesting JD during nursing.
- Weaned replacement heifers housed with cull cows in a closed confined feeding area.
-- Clint Peck