Why waste money rearing BVD calves?
Firstly, there is the grazing cost
associated with raising a carrier or 'persistently infected' (PI) animal that will eventually be culled. The cost of testing for PI animals is minor compared to the $300-400 spent grazing a calf followed by the $500-600 grazing a heifer.
Secondly, there are reduced growth rates
associated with the presence of PI animals. PI animals themselves have reduced growth rates and their presence in a group will also reduce the growth rates across that group. In an American study, vaccinated calves housed with or next to a PI had 20% lower average daily gain.
Finally, by identifying PI animals as calves
, they are prevented from entering the herd. A recent New Zealand study found losses of $87 per cow in herds exposed to BVD. These losses were mostly in herds that are vaccinating and studies from the United States of America have indicated the presence of PI animals in vaccinated herds can still reduce production by 2-3%.
It is easy to test young stock
for the presence of PI carriers:
- Testing of call calves - carrier animals can then be culled early in life, calves testing negative can be permanently recorded as being clear of BVD
- Alternatively, a blood test of 8-10 calves, for example at the time of their lepto vaccinations, can be taken. If this sample tests positive it indicates the presence of a PI in which case we need to bleed or ear notch the whole group. If the sample tests negative it proves there are no PI animals in that group. The blood sample also provides an opportunity to test the mineral status of these animals. Mineral testing is often overlooked in young stock despite being the group where supplementation of deficient animals is likely to have the most impact.
Please contact your branch of Franklin Vets if you have any questions regarding BVD in your herd, or would like to look into testing your young stock.