As we start testing and vaccinating breeding bulls for BVD, it is a good time to review the diseases effect on breeding animals, why we test, vaccinate (both bulls and heifers) and what is now happening in New Zealand to work towards this diseases eradication.
In New Zealand, about 65% of beef herds are infected with BVD, and most beef herds have been infected at some point.
The infection can cause ill-thrift in young stock, and infertility and production losses in adult cattle.
When breeding cows are infected you likely won’t see any obvious direct ill-health effects in that animal. However, the effects on fertility and on the unborn calf can be profound, including low in-calf rates, abortion, stillbirths, birth of “dummy calves” and the birth of persistently infected (PI) calves who are the carriers of the BVD virus. Bulls infected with BVD transiently can have reduced semen quality.
In beef herds economic losses are associated with ill-thrift in young stock and on average, a 5% increase in empty cows.
Testing can show level of herd exposure (by looking at antibody responses), group or individual infections (by looking at antigen/virus shedding). Infection can be transient or persistent, and persistently infected animals are created from exposure to the virus while in the womb.
The testing done depends on the mob we are looking at- all bulls are tested individually to ensure they aren’t persistently infected before sale, while if we want to know herd levels of exposure a group from the replacement mob is best.
We vaccinate bulls so that if the mob they are going into has the virus they (and their fertility!) are protected from becoming transiently infected.
Heifers are vaccinated to protect themselves and their calves. If the virus passes through a cow while they are pregnant, depending on the time of infection, the calf could be aborted, become a dummy, or become a persistently infected animal.
In July 2017, a new, exciting three-year Sustainable Farming Fund programme was launched to build the business case for eradicating bovine viral diarrhoea virus (BVD) from New Zealand cattle herds. The BVD free group plans to work in close partnership with farmers and veterinarians from across the country to learn more about how BVD currently impacts their business and how much national eradication could save the industry long term.
As part of the national campaign running from July 15 2018 to May 15 2019, be one of the first 500 beef and dairy farmers to register on the BVD Free website and you may be eligible to receive a free BVD youngstock screening test for your herd.