Bulk Milk testing
As part of your regular herd test LIC offer a Bovine Viral Diarrhoea (BVD) bulk milk test. This test will measure two aspects of your bulk milk sample in relation to this disease.
- The first is the SP ratio which is looking at antibody levels. This is the paint ball splat with a letter in the middle appearing on the graph. If the levels are high it means the cows have been exposed to BVD and are actively producing antibody, if low they are less likely to have been exposed and hence antibody is not being actively produced. If the levels are somewhere in between it may mean that in the past the herd was exposed but the antibody levels are declining, or a BVD free herd may have been recently exposed and therefore the antibody levels are increasing.
- The second thing measured is the presence or absence of virus (different to the antibodies which are produced in response to exposure to the virus). This is represented by the arrow at the top of the graph. If you get the red arrow it tells us that one of the cows that contributed to the vat on the day they were tested is a carrier, if you get a clear arrow then there are no carrier cows amongst the cows that contributed milk to the vat that day. Remember, that is not to say that there isn’t a carrier cow in the penicillin mob or in the younger stock.
In general, a low antibody level (yellow or orange splatter) tells us that your herd has low level of exposure to BVD. That’s fine if your herd is biosecure, but you are at risk of a more severe outbreak if it is introduced. A high antibody level tells us your herd has a high level of exposure and is likely to have been exposed recently to BVD, usually meaning that there is a carrier lurking somewhere in your herd.
There is no one size fits all solution to BVD. The best thing to do is, armed with your most recent LIC splatter and arrow graph, accost your friendly vet next time he/she is on the farm to work out what would best work for you.