BVD is a viral infection prevalent in approximately 15% of dairy herds. Despite its name, BVD doesn’t always cause diarrhoea; in fact, around 70-90% of infections occur without clinical signs. However, it can have significant impacts on animal health, welfare, production, and reproductive performance.

 

Effects of BVD:

• Adult Bulls: New infections can reduce fertility for up to 10 weeks.

• Adult Cows: They may experience fevers, decreased appetite, diarrhoea, and depression. While they develop immunity (abortions can still occur), their milk yield is reduced by around 5% if regularly exposed to a Persistently Infected (PI) animal.

• Calves: Those exposed after birth to the virus may exhibit scours, rough coats, and reduced immunity. Their growth rate is approximately 20% lower if reared with a PI calf.

• Foetal Calves: Above 150 days of gestation, the foetal calf can mount an effective immune response, usually being born immune and undamaged. Foetal calves infected under 150 gestation days may be aborted, have birth defects or become PIs.

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Sources of Infection:

• Brought-In Animals

• Bulls

• Contact with Other Stock

• Runoff/Grazing Areas

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Monitoring and Prevention:

• Bulk Milk Testing: An easy and reliable method to monitor your herd’s BVD status.

• PI Hunts: If the bulk milk test is positive (indicating active virus shedding), conduct PI hunts to find and eliminate existing PI animals.

• Vaccination:

  • Vaccinations for BVD can begin at 3 months of age and require a booster vaccination approximately 4 weeks later. 

  • For many of our clients, young stock (calves and heifers) are routinely sent out to grazing. We strongly advocate vaccinating these animals before grazing to mitigate potential exposure risks.

  • Heifer vaccination should be done prior to mating or grazing.

  • In some instances an annual whole herd vaccination may be recommended, particularly in high-risk scenarios. This is often done prior to mating.

• Biosecurity Measures: Reduce contact with other farms animals.