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To Control Johne’s Disease, Scientists Seek Help From U.S. Dairy Producers

A research team from the University of Wisconsin-Madison is enlisting the help of hundreds of U.S. dairy producers in an effort to prevent Johne’s disease. Johne’s may be the most serious infectious disease now threatening the U.S. dairy industry.

The team believes their results will help the industry score sires based on the resistance of the sires’ daughters to the disease. In the long term, the researchers want to identify the genes responsible for susceptibility and resistance to Johne’s.

“Studies indicate that about 10 percent of U.S. dairy cattle – and between 20 percent and 40 percent of herds – have Johne’s disease,” says team leader George Shook, a dairy cattle geneticist at the College of Agricultural and Life Sciences. “Johne’s costs producers about $200 million a year, which averages out to $22 per cow per year for each cow in the United States.”

Joining Shook in the Johne’s study are Brian Kirkpatrick, also a cattle geneticist at CALS, and Michael Collins, a veterinary microbiologist in the School of Veterinary Medicine.

“Johne’s is a slowly developing, incurable disease caused by a chronic intestinal infection,” says Collins, who specializes in the disease. The infection interferes with an animal’s ability to absorb nutrients from food. The disease is also called paratuberculosis (after Mycobacterium paratuberculosis, the bacterium that causes the infection).

“It’s a difficult disease for most dairy producers,” says Shook. Cows usually pick it up as calves. It develops slowly until cows begin to produce less milk and lose weight. Meanwhile, infected animals can pass on the disease to the next generation. Producers cull cows with Johne”s from their herds, sometimes without realizing what caused their illness.

Because there is no treatment for Johne’s disease, the researchers will look for the genetic basis of resistance and susceptibility to the disease. “Preliminary research in the Netherlands suggested that resistance in cattle has a genetic component,” Shook says. “A mouse model of the disease even points to a gene that may be involved in resistance.”

To discover a link between Johne’s disease and cattle genetics, the researchers must have data on a huge number of cows from individual sires. The scientists are focusing on cows from 15 Holstein sires, all from major artificial breeding organizations.

“We”re focusing on these 15 sires because we need to analyze samples from at least 800 daughters from each sire. So we selected sires that have 5,000 to 8,000 daughters in production,” Shook says.

To complete such a large effort, the researchers need help from producers around the country.

The researchers have begun to survey herds in the Dairy Herd Improvement program. They want to begin with herds that have at least one cow that has developed Johne”s disease. The researchers then send cooperating producers a list of their cows that belong to the 15 sire families. Producers then have their local vet collect blood and fecal samples from those cows during the vet”s next regular farm visit. That might cost producers about $3 to $5 per cow, according to Shook.

In return the researchers will conduct tests on those samples and send each producer – not his or her veterinarian – a free report of the results for each cow tested from that herd. Two diagnostic tests will be run for each cow – a fecal culture and an ELISA antibody test. The tests will be done by the Johne’s Testing Center in the UW-Madison Vet School. Shook estimates the cost of these tests at more than $20 per cow if producers were to order them on their own.

The USDA Initiative for Future Agriculture and Food Systems is providing most of the support for the two-year study. The researchers also have received support from National Association of Animal Breeders and a Hatch grant from the UW-Madison College of Agricultural and Life Sciences.