Strategies to Combat Bovine Viral Diarrhoea in New Zealand Dairy Herds
Bovine Viral Diarrhoea (BVD) poses a significant financial burden on New Zealand's dairy and beef industries, with estimated costs exceeding $150 million each year. The persistence of this issue is largely attributed to the presence of persistently infected (PI) animals, which are infected before birth and spread the virus throughout their lifetime.
Andrew Weir, an animal health technical specialist at LIC, emphasizes the importance of identifying and removing PI animals to control BVD. A case study involving a herd of nearly 1,000 cows revealed that a single PI cow could lead to the infection of over 95% of susceptible animals within four months. This highlights the efficiency of PI animals in spreading the virus.
To protect herds, especially during spring calving, farmers are advised to vaccinate heifers or ensure BVD-free grazing. Vaccination helps prevent PI calves, while BVD-free grazing involves testing all animals on grazing properties. This method offers additional benefits, such as improved confidence in the health status of returning animals.
Most New Zealand dairy herds conduct bulk milk testing, a critical step in BVD control. However, comprehensive control programs that include herd vaccination and calf screening tend to be more effective. Screening replacements is often more cost-efficient than annual vaccination of all adult cows, and both strategies have proven successful.
The reduction of infected dairy herds from 15% to just under 5% demonstrates progress, yet recent plateaus suggest the need for further action. The BVD Status Pack provides a reliable method to confirm the BVD status of individual animals, and increased testing and purchase of BVD-free animals could further reduce infection rates.
Farmers benefit from a healthy herd, enjoying the satisfaction of ensuring the best care for their cows. The industry stands to gain from continued efforts to drive down BVD infection rates, fostering a healthier and more productive future.
