Getting maximum value from the BVD Test. Scotland’s cattle farmers and their vets have made huge progress towards BVD eradication. To comply with the BVD eradication scheme rules, breeding herds must update their status annually. Keepers can choose between Check Testing and All Calf Testing. Check testing is not always fully-understood, we hope this explainer helps farmers and vets to make the most of this useful, cost-effective test.
What is a check test?
The BVD Check Test relies on your vet to blood sample representative youngstock from your herd. The laboratory will test the samples for BVD antibody (showing exposure to disease). Done well, the Check Test is a sensitive, accurate way to see if the youngstock have been exposed to BVD. This means sampling all management groups of youngstock in your herd. A separately managed group consists of those animals that can feely achieve nose-to-nose contact with all others within the group. A single set of 5 or 10 animals is not enough if you have a large herd or if there are several different groups. Work with your vet to determine how many management groups there are, and then select the most representative animals for sampling.
What does a positive result mean?
A Positive Check Test result may indicate PI (persistently infected) animals in the herd, or exposure to PI’s elsewhere (e.g. neighbouring herds, in the market, at shows) that could result in PI calves being born in the next year. A positive result, even if it is only one sample from the whole set, means that you will need to do further BVD testing to determine the extent of the problem. Speak to your vet about the best approach for your herd.
Prompt investigation can reduce future BVD problems in your herd
Farmers with personal experience of BVD breakdowns use the Check Test as an insurance policy: if any of the samples are positive, money spent on additional testing is the price of investigating the problem & dealing with it as swiftly as possible.
Experience suggests that a single Positive result is an early warning
As above, if the Check Test shows only on Positive animal, follow your vet’s advice on further testing to establish the extent of the problem in your herd. In cases where only that single animal remains strongly Positive at re-test, BVD exposure has been limited but it may result in PI’s in the next calf crop. The safest response is to test every calf born in the following 12 month period for BVD virus/antigen, which will detect any PI calves.
Getting back to a BVD Negative herd status after a Positive Check Test
Consult your vet on the most effective strategy. Depending on your circumstances, appropriate testing will allow you to find & eradicate BVD in your herd OR prevent PI calves from being born (or find them as soon after birth as possible) OR will give the herd a clean bill of health (no evidence of BVD exposure).
Successful Check Testing
Allow the vet to select representative young stock in the age range 9-18 months old (younger & older animals may be suitable in exceptional circumstances)
All should be homebred.
Make sure every youngstock management group is sampled.
Avoid vaccinated animals – they may give a positive result.
Don’t forget youngstock that are away from home: they might have been exposed to BVD & could have brought it back to the main herd.
