Worried about disease striking your herd? You're not alone. The uncertainty of when and where disease might strike has made vaccination increasingly important. Learn more in this month's Health Focus about why, when and how cattle should be vaccinated.

	Cattle Vaccines and Their Use
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	Immunizing Beef Calves: A Preconditioning Immunization Concept
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FEATURE STORY:

Immunizing Beef Calves: A Preconditioning Immunization Concept
Infectious diseases cause sickness and death in calves, before or after they are born. Unborn and nursing calves are at high risk to fatal diseases during the time of year when a beef rancher is calving cows, moving and mixing these cows, and bringing in bulls to them.

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A new three-stage program to help beef and dairy cattle producers control Johne's Disease within their herds has been developed jointly by the College of Agricultural Sciences and the Pennsylvania Department of Agriculture. Penn State's role in the program is to provide educational materials for farmers and veterinarians and to provide training for both veterinarians and industry professionals.

Johne's Disease (pronounced yo-knees), a bacterial disease of cattle and other ruminants, is related to the bacterium causing tuberculosis. The disease has a long incubation period--one to five years--before signs of infection are obvious. Symptoms include weight loss, diarrhea, and decreased milk production in dairy cattle. "Once cattle contract the disease, it's incurable," says veterinary scientist Larry Hutchinson. "It's estimated that 20 to 40 percent of Pennsylvania's dairy herds have cattle with Johne's Disease."

"Beef cattle have it as well, but at a lower frequency," adds David Wolfgang, senior research associate in veterinary science. "Dairy herds are housed and managed in much closer proximity than beef cattle, which makes it easier for the Johne's Disease pathogen to spread."

The Pennsylvania Johne's Disease Program is a voluntary tool that can help producers identify whether their herds are infected and control or eliminate the disease. "If a producer does nothing to prevent the spread of Johne's Disease, the dairy operation will eventually decline in production," Wolfgang says. "There also may be other economic consequences, such as a lower price for culled cows and a decline in fertility."

The first step in the state program is the "30 Free" test. Producers can test any 30 adult animals in their herd for the disease with no laboratory fee, although veterinarians will charge a fee for drawing blood samples. "The test program does not obligate producers to do anything if their herd has animals with the disease," Hutchinson says. "Testing 30 animals will give large and small operations an idea of disease prevalence in the herd."

If testing proves the herd is not infected or has low prevalence of the disease, producers can enlist in the Voluntary Johne's Disease Status Program, which features four herd health levels that producers can use to keep their herds disease-free. "Producers can choose to move up to different levels or maintain their status in the same level," Hutchinson explains. "It depends on the farmer's economic and management goals. If you have a small operation and market embryos or bulls, you may want to move up your status. If you have a large operation and buy new cows, then you probably would prefer to maintain or improve status gradually."

The program's second level involves targeted testing for the herd, including all adult cows. The testing fees are reduced as long as farmers participate in the program. The third level of the program tests more cows and uses a more accurate fecal culture test. In the fourth level, herds that test free of Johne's Disease are certified, and producers return to periodic blood tests.

Producers with infected herds can enter the Voluntary Johne's Disease Management Program in conjunction with their veterinarians. The producer and veterinarian are required to write a herd management plan and meet goals to improve herd health. "This program is completely voluntary and does not have strict timetables to cull infected animals or eradicate the disease if your herd is infected," Hutchinson says.

The most important part of the program is writing and following a management plan in which the producer and veterinarian assess management areas to determine where the herd is most at risk for infection. "The management plan will identify areas of greatest risk of disease transmission," Wolfgang says. "The producer and veterinarian will work to reduce transmission in those locations at a pace comfortable to the farmer."

Farmers and other interested professionals can get educational material and information on the Johne's Disease program at all Penn State Cooperative Extension county offices. For more information, contact Larry Hutchinson at (814) 863-2160 or David Wolfgang at (814) 863-5849.

--John Wall

Reprinted from Penn State Agriculture Magazine, Winter/Spring 2000