The High Risk [Cow-Calf] Herd
"The greatest achievement of the human spirit is to live up to one's opportunities, and to make the most of one's resources". - Vauvenargues
A lot has been written on the significance of bovine viral diarrhea virus [BVDV] persistently infected animals in a cow-calf herd, or dairy, and less frequently the feedlot. The opportunity that has to be seized is to use resource tests available at most diagnostic labs in the most economically beneficial way to achieve the producer's goals to reduce problems associated with BVDV. The Academy of Veterinary Consultants has recently published suggestions for BVDV Decision making processes and management guidelines for veterinarians.
What makes a herd "high risk" for potential BVDV problems? Often it is animals that suggest persistent infection by visual examination; it also includes evidence of:
- Poor reproductive performance despite good nutrition and bull fertility
- High calf morbidity/mortality despite good sanitation and nutrition
- Laboratory testing has previous confirmed evidence of BDV transient [acute] infection [TI] or BVDV-PI animals have been previously identified
There are many tests that are available to use in a regimen to identify persistently infected animals; however, testing needs to start BEFORE the breeding season, goals need to be known, and achievable, and a plan of action needs to be in place. Click here to see a list of tests and fees conducted at ISU VDL.
- All calves should be tested. The IHC (immunohistochemical) test on ear notches is appropriate for cattle of all ages, and is considered the test of choice, for young animals particularly
- All cows without calves [open cows or calf died]. There is a broader spectrum of tests that are available for this group of animals. Depending on what other tests may be indicated for evaluation of herd health status, such as leptospiral serology etc. tests available include:
- IHC on ear notches [tests for BVDV-PI status]
- Ag-capture ELISA [Animals should be 6 months of age or above]
- Virus isolation
- Polymerase chain reaction
- All replacement bulls and heifers [purchased or raised]
- Ag-capture ELISA
- Virus Isolation
- Polymerase Chain reaction
- Calves that test positive.
- Remove the calf and dam from the herd to reduce exposure of others to BVDV
- Remove the calf
- Test the dam
If the dam tests negative, she may return to the breeding herd, if she is positive she should be sold for slaughter.
Heifers, bulls, and open cows which test positive for persistent infection should be sold for slaughter. Those which are negative may be retained in the herd.
Keep in mind that the absence of confirmed PI calves does not guarantee absence of a BVDV problem. If you are still suspicious additional testing is warranted.
Also keep in mind that without adequate attention to vaccination programs and biosecurity concerns, simply removing PI cattle from the herd will not necessarily remove a BVDV or any other disease problem.
Dr. Vickie Cooper
Veterinary Diagnostic Laboratory
Iowa State University
1800 Christensen Drive
Ames, IA 50011