As we get nearer to spring calving season, our clinic will begin to get calls of aborted fetuses, near-term stillbirths and lost calves. These cases can be frustrating, as often we will not get a definitive diagnosis of what caused the problem. It is important for producers to understand a couple of things when deciding if it is worth the expense and effort to run diagnostic tests on individual ill or dead animals.
First, we are dealing with a herd of animals—not individual animals. If you have a herd of one cow and it dies, doing a necropsy is of limited benefit. With a group of animals, we are looking for causes that will affect other animals in the herd.
Bovine viral diarrhea (BVD) is a prime example. BVD can cause huge losses and can often be found with routine necropsy and diagnostic testing on ill and dead animals. The cost-to-benefit ratio of finding this disease goes far beyond the benefit of finding it in the sick animal. Because BVD is not a treatable condition, that animal receives no benefit. Only by testing animals that are most likely to be affected by BVD will you increase the likelihood of finding the cause.
Beneficial information. Secondly, understand that a negative test is not useless information. In fact, it can be invaluable in diagnosing a herd problem. By ruling out specific diseases, we narrow down the possibilities of what may actually be causing the problem.
Do we run diagnostics on every sick and dead animal? No. Experience has taught me, though, that we often wish we could have back the aborted fetus we decided not to test. It usually turns out to be the best sample able to be collected and it is no longer available when a herd issue develops.
Be aware that even when you are in the middle of a disease outbreak in the herd, you may still have cattle that are sick for a different reason. There will also be cases where tests come back negative that are truly positive for disease. For these reasons, testing more than one animal is important to the accuracy of results. Work with your veterinarian to decide what diagnostics are appropriate for your operation.