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Bovine Viral Diarrhoea - BVD in Dairy HerdsBVD is now widely regarded as endemic in the UK national dairy herd and, although we don’t seem to be moving towards a countrywide eradication policy, controlling this nasty disease on a farm-by-farm basis will improve many areas of cow performance.BVD vaccines have been on the market for several years, and herds that incorporate them into their preventative healthcare strategies see clear benefits. However, getting vaccine timing right is essential if stock is to be properly protected. Planning when heifers are vaccinated is a crucial starting point, as vaccine should be administered before they are pregnant. If vaccination is late and she is already in calf, the early part of the pregnancy won’t have been protected from the virus. If she has been exposed to BVD while unprotected, both heifer and developing foetus can be affected sometimes resulting in late abortions, or alternatively in a PI (Persistently Infected) calf being born. PIs are animals born seemingly healthy, but they ‘shed’ virus to herd mates. This usually occurs when an unprotected dam is exposed to the BVD virus in the early stages of pregnancy. PI animals often appear normal and can go on to develop within a herd. If these animals get in calf they will always produce another virus positive animal. Once a PI is within a herd, any unvaccinated stock is at risk. There are two parts of the control and management of such a situation. Bulk milk screening which checks the level of infection in a herd and will show whether or not the BVD virus is active in the herd. Once the herd’s disease status is understood, a vaccination an individually tailored vaccination programme can be put in place. It is worth remembering that animals infected with the BVD virus will have a reduced immune system. This means that they are more susceptible to other diseases such as IBR and some experts believe they may suffer higher levels of mastitis. Contact one of the vets to discuss how to establish your herd’s BVD status and options for vaccination. |
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