EAST LANSING, Mich. — When the National Animal Health Monitoring System released its comprehensive report on Johne’s disease in 1997, the majority of dairy producers had only a general idea of what the disease was, and fewer still thought it affected their herds.
But with an estimated 50 percent of the dairy animals in Michigan infected with Johne’s disease, there was no doubt it was a serious industry priority.
Enter Michigan State
Several Michigan State University researchers sought funding to learn more about this economically damaging animal health issue, which has an estimated $200 million annual impact on the U.S. dairy industry.
Read Johne’s Disease on U.S. Dairies 1991-2007 (link opens pdf).
Central to the initial research efforts was Dan Grooms, MSU associate professor of large animal clinical sciences and a large animal veterinarian. Along with learning more about the disease, Grooms and his colleagues from MSU and other universities would work for several years to determine the best management practices to employ on a dairy farm to prevent the spread of the disease and lower the percentage of animals infected (prevalence rate).
National survey
In 2003, researchers and veterinarians from the MSU Department of Animal Science, College of Veterinary Medicine and the Diagnostic Center for Population and Animal Health, and the Michigan Department of Agriculture joined researchers from 16 other states to monitor dairy herd management practices. The Michigan team was chosen to be a part of the USDA’s National Johne’s Disease Demonstration Project.
Grooms selected seven herds to serve as his Johne’s disease demonstration herds. The herds, located in various regions of the state, underwent whole-herd testing to measure baseline levels of infection. From there, a disease risk assessment was conducted, and management practices were put in place to help control on-farm spread of the disease.
“We know that animals are most susceptible to Johne’s infection at a very young age, so calf management was our first priority,” he said.
“There is no cure for Johne’s, so the best way to manage the disease is to prevent it.”
Sign me up
At the same time that Grooms was assembling his herds for the demonstration project, Galen Schalk, a dairy farmer in Hillman, Mich., encountered his herd’s first diagnosed case of Johne’s disease.
“I had heard about Johne’s disease but thought, ‘That’s not me,'” Schalk said. “We have had a closed herd since 1974, so because I was not bringing new animals into the herd, I didn’t feel we were at risk for the disease.”
The first Johne’s test from the Schalk’s herd, run at the request of his veterinarian, came back positive for Johne’s. The diagnosis concerned Schalk, who contemplated how many other cases he might have in the herd, so when Grooms approached him to be part of the Johne’s disease demonstration project, Schalk did not hesitate to sign up.
“I had a very minimal understanding of Johne’s and minimal prevention practices when we started with this project,” Schalk said.
Throughout herd
The first round of fecal cultures from the Schalk herd came back with a 21 percent prevalence rate among the 168 animals tested; the second year, 2004, the rate jumped to 42 percent.
The more Schalk learned about the disease and the test results on his herd, the more he realized that he had seen cows develop clinical signs of the disease in the past but hadn’t realized it was Johne’s.
“We would have cows get really thin and drop in productivity, so we would cull them from the herd,” Schalk said. “Now I know they were Johne’s animals.”
Targeted calving area. Seeing the high prevalence rate, Schalk was eager to eliminate the problem as quickly as possible. Schalk, Grooms and other MSU scientists put together new management strategies to help control the disease.
The area of highest concern on the Schalk farm was the calving area. Cows calved on a manure pack, which created the perfect environment for disease organisms to survive and spread to newborn calves. Though the Schalks had already drawn up building plans for a new transition barn, they opted instead to construct a new maternity and housing area for close-up cows.
“It was good that we were already looking to put up a new building because we really needed a better place for the animals to calve in,” Schalk said.
Along with building the new maternity area, Schalk started withholding the colostrum from Johne’s-positive cows and feeding newborn calves colostrum from only noninfected cows.
“Johne’s can be transmitted to the calf through the colostrum or from the contaminated environment,” Grooms said. “Knowing which cows are positive for Johne’s is critical in stopping the disease from spreading.”
Sanitation critical
The new maternity area also provided an opportunity for each cow to calve in its own pen and allowed Schalk time to clean and disinfect each pen between calvings.
Because animals contract Johne’s disease early in life, properly caring for calves is one of the most critical steps in preventing disease transmission, even though measuring immediate results from changing management practices is difficult.
“Even though we culled a number of animals during the first two years of the project, we still need to manage for the disease because we know some of the older animals are carriers,” Schalk said.
Cows tagged
Visually identifying the Johne’s carriers helps Schalk manage the disease. Schalk now tags all animals that test positive for Johne’s disease with a special red neck chain. Any heifers born to positive dams are also tagged with the red neck chain until they receive a negative test reading.
“It is not perfect,” Schalk said. “Occasionally an animal is born early in the close-up area and not in the assigned calving pen, but we are really making progress.”
Cross-contamination
Animals can shed the organism that causes Johne’s even if they are not showing clinical signs of the disease. Research indicated that the disease-causing organism is shed through the manure. So Schalk implemented another critical management practice — taking preventive measures to ensure that no manure comes in contact with animal feed.
To prevent cross-contamination, the Schalks bought a second skid steer and use one only to clean and scrape manure and the other only to handle and move feed. They also make sure not to cross over feed alleys with equipment to minimize the risk of any manure on the tires coming into contact with the feed.
Since the Schalk herd became part of the Johne’s demonstration project, the prevalence of Johne’s in the herd has dropped to less than 5 percent. The results on this herd are similar to the outcomes realized by the other test herds.
“We saw a reduction in the number of Johne’s-positive animals in all the herds we worked with,” Grooms said. “This project shows us that, though there is no cure for Johne’s disease, with proper management farmers can prevent the spread of the disease on their farms and reduce its prevalence over time.”
As the demonstration project winds down, Schalk is looking ahead to how he will continue implementing the recommended management practices on his farm. Now that he has the prevalence rate down to less than 5 percent, he will continue to test the herd to monitor for any new infections.
“We were surprised to learn that we had the disease at all. If we don’t continue to test the herd, we won’t know if we’re continuing to make progress,” Schalk said.
