Montana BVD PI Herd Screening Project

By Lisa Duffey, Montana Beef Network Coordinator with Clint Peck, Senior editor, BEEF Magazine.

The beef and dairy industries suffer enormous loss due to effects of bovine viral diarrhea virus (BVDV) infection. The highly mutable nature of BVDV and the emergence of highly virulent strains of BVDV contribute to limited success of present control programs. Also, persistently infected (PI) cattle are the primary source of infection and effective testing procedures are available to identify those infected carriers.

Therefore, it is the resolve of the Academy of Veterinary Consultants that the beef and dairy industries adopt measures to control and target eventual eradication of BVDV from North America. - Position statement on Bovine Viral Diarrhea Virus, Academy of Veterinary Consultants, approved by majority vote of membership, November 2001.

The Montana BVD-PI Herd Screening Project is sponsored by Montana State University and the Montana Stockgrowers Association. The project‹s goal is to investigate the role of BVD PI screening in improving the overall health of Montana‹s cow herd and adding value to the state’s calf crop. The voluntary project is providing technical assistance and limited financial support to Montana ranchers who want to screen their herds for BVD PI status.

BVD PI screening should be part of a program involving vaccination, biosecurity and overall herd health management. The screening protocol assists the producer in finding all PI animals in the herd and also assures that new arrivals are BVD PI free.

BVD PI Herd Screening Project Recommendations

Test animals before bull turn out to avoid exposure of a PI during breeding.
Sampling is based on a small ear notch placed in a dry tube kept cool or frozen.
The same tissue sample used for initial pooled reverse transcriptase polymerase chain reaction (PCR) screening is the source sample for re-testing to identify individual "reactors" in the pool.
Cows do not need to be sampled and tested unless they have a positive PI calf.
Individual animal identification is critical to match all samples with the animal tested and match the calf with its dam.
A plan should be developed to eliminate PI animals from the herd.
If an animal tests negative for BVD PI status, there’s no need to retest that animal.
PI surveillance should include the necropsy examination of as many aborted fetuses, stillborns and pre-weaning deaths as possible.
PIs that live to be breeding females can horizontally transfer of the virus to other animals in the herd − and they will always produce a PI calf.

Test new entries into the herd:

Home−raised yearling heifers−heifers should be tested prior to breeding for BVD PI status. If the heifer was tested as a calf and found to be negative there is no need to retest.
Purchased open heifers−All heifers should be tested before purchasing or before commingling with herd and the start of breeding season.
Purchased bred heifers or cows−All heifers or cows with an unknown BVD PI status should be kept separate from the home herd. Calves from these animals must be tested prior to commingling.
Bulls−Should be purchased as BVD PI tested free. If not, bulls should be tested prior to breeding season. A good time to take an ear notch is when doing breeding soundness exams.

Calves

All calves born alive should have an ear notch sample taken prior to bull turn-out. Ear notches can be frozen for up to 30 days, facilitating sampling over an extended period of time.
All calves aborted, stillborn or that died before normal sampling time should have an ear notch sample taken.
All grafted calves purchased should have an ear notch sample taken.

Cows