There may be justification on a herd-by-herd basis for continued whole-herd screening, especially calves from younger cows (2- and 3-year-olds), if:

• Any PI or transiently infected animal is found in the herd, or if there's unusual sickness, reproductive failures, abnormal births, calving losses, etc.

• A serious biosecurity breach (in-common grazing situations, fenceline contact with suspect animals, accidental mixing of breeding herds, etc.).

• Risk for other reasons (suspected vaccination failure or gaps in vaccination protocol).

The Montana BVD-PI Herd Screening Project plans to screen at least 100,000 Montana calves in 2007, with support from the Montana Stockgrowers Association, implementing the same basic protocol as 2006. This will take a concerted effort on behalf of ranchers, veterinarians and others in the industry. But the rewards will be reduced sickness and subsequent treatment for disease, and an improvement in the health of the state's overall calf crop.

The challenge is for other states to develop programs designed to find and eliminate as many BVD-PI cattle as practically possible. This is the most reasonable means of getting a handle on this disease nationwide.

Finally, Montana project managers highly recommend all ranchers work with their attending or consulting veterinarians to develop a herd-health protocol that considers all BVD virus risk factors and incorporates the above management components, including a common-sense biosecurity program.

Clint Peck, Billings, MT, is former Senior Editor of BEEF magazine.

Screening on the ranch for cattle persistently infected (PI) with bovine viral diarrhea (BVD) should be part of a program involving vaccination and herd biosecurity. The screening protocol assists the producer in finding all PI animals in the herd and reduces the BVD-PI risk in new arrivals.

Some points to remember:

• Transient BVD virus infection differs from persistent infection.

• PI calves are “created” during gestation.

• Born a PI, always a PI.

• Not born a PI, never a PI.

• Test the herd before bull turnout.

• PI females will always produce a PI calf.

• Mature cows normally don't need screening unless they have a positive PI calf.

• Individual ID is critical to match all samples with the animal tested and match the calf with its dam.

• Cattle testing negative for BVD-PI status never need to be retested.

• PI surveillance should include the necropsy examination of as many aborted fetuses, stillborns and pre-weaning deaths as possible.

• A plan should be developed to eliminate PI animals from the herd.

For more on the Montana BVD-PI Herd Screening Project, visit www.mtbqa.org and search under “Projects.”

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