BVD stands for a viral disease called Bovine Viral Diarrhoea. It is estimated that around 60% of cattle in New Zealand are exposed to this virus during their lives. It was originally thought to just cause diarrhoea in young cattle but now we know that the virus's main economic impact is through its effect on cattle reproduction and their immune system.
The stage of pregnancy that a pregnant cow picks up the virus will determine the effects on her reproductive performance. Cows can show up as being empty due to early embryonic loss. They can abort later in pregnancy or produce calves with congenital defects. Or, most seriously, they can produce calves that become infected with the virus during pregnancy that become carrier animals after birth. These cattle shed virus for the rest of their lives and are known as Persistantly Infected animals (PI)
We are currently well into the BVD testing and monitoring season for dairy farmers pre mating.
This year up to 25% of dairy herds have a carrier cow milking into the vat. Given that beef herds generally reflect these levels (or higher), BVD is alive and well in the Wairarapa. Infected dairy heifers have also been found in herd screening.
BVD control in beef herds is based around 4 key steps:
1. Assess the BVD status of the herd
2. Define the status of the herd
3. Actions to control BVD
4. Monitoring the status of the herd
Because BVD carrier animals (Persistantly Infected) are generated on the farm they are born on, it is important that farmers selling weaner cattle and bulls are aware of the risks of selling other farmers infected cattle.
Be aware that there are biosecurity risks presented when introducing dairy heifers or winter grazing dairy cows - BVD can travel over fences, so either the new arrivals, or your own cattle present risks to each other.
Talk to your vet about how to manage BVD for your operation.