Controlling and managing the spread of Johne's disease is a priority in dairy operations of all sizes, but farm managers at the Michigan State University (MSU) Dairy Cattle Teaching and Research Center have an even greater incentive riding on achieving this goal than do most: diagnosing a cow infected with the disease can result in erroneous data results on university-led research projects.
Though Johne's disease, a contagious and untreatable disease caused by the bacteria Mycobacterium paratuberculosis, or MAP, typically occurs in calves, animals generally don't express clinical signs of the disease until later in life.
So, in 2002, the MSU Dairy Cattle Teaching and Research Center signed their cattle on as a test herd for the Johne's Disease Control Demonstration Project, a near decade-long research project conducted by MSU researchers and MSU Extension specialists that evaluated Johne's disease control strategies in an effort to identify which management practices are the most effective at controlling the spread of the disease.
"We were very interested in participating in the Johne's Disease Control Demonstration Project," said Bob Kreft, farm manager at the MSU Dairy Cattle Teaching and Research Center. "We wanted to identify and quickly eliminate any Johne's from the herd because if our animals are Johne's-positive, it can confuse the other research going on in the barns."
The herd's 250 head of lactating dairy animals were tested for the disease and any animals confirmed positive with Johne's were culled. The project team members also conducted an on-farm audit for possible areas of transmission and determined that the two areas of concern were the calving area and the practice of feeding pooled colostrum to newborn calves. Though testing had confirmed that the prevalence of the disease in the herd was very low, Kreft worked with the research team to modify management practices to reduce it even farther.
To control the spread of Johne's disease in the calving area, farm employees designed warming boxes for outside of the maternity pens. Now, as soon as calves are born, they are transferred from the pen in which they're born to one of these separate calf boxes. The boxes are built on an elevated, grated floor equipped with small space heaters that can be turned on during cooler weather.
Additionally, the tractor and feed mixer no longer travel through areas in the barn where there may be manure. MAP can be spread throughout the barn when manure clings to the tires of farm equipment. The tractors now drive into the feeding alley, backing out after delivering feed instead of driving over the areas where the cows walk. This eliminates the spread of MAP.
Animal pens have also been rearranged so that the breeding-age heifers don't come in contact with the milking-age animals. Previously, the two groups were only separated by a gate, which still allowed contact between the younger and older animals.
"On this farm, a heifer doesn't meet a cow until she's 22 months of age," Kreft said.
MSU continues to monitor the herd's progress by conducting herd tests at mid-gestation and when cows calve. Despite the aggressive strategy, occasionally an animal tests positive for Johne's, further justifying the importance of having a long-term evaluation and management strategy in place.
The Michigan Johne's Disease Control Demonstration Project was a partnership between the MSU College of Veterinary Medicine and Diagnostic Center for Population and Animal Health, MSU Extension, the Michigan Department of Agriculture and Rural Development and the U.S. Department of Agriculture in collaboration with nine Michigan veterinary clinics. Findings from the Michigan farms involved in the study were pooled with data collected from 17 other states as part of the larger, multi-state project, the National Johne's Disease Control Demonstration Project.
Find additional information on the Michigan Johne's Disease Control Demonstration Project at http://cvm.msu.edu/johnes.