Bovine viral diarrhea (BVD) can lead to significant outbreaks of respiratory disease in stocker and feedlot operations, and that is where the disease often is most visible. Control at the cow-calf level however, can help prevent those losses, while also reducing the risk of costly reproductive problems. But, says, Kentucky State Veterinarian Robert Stout, cow-calf producers often do not see or recognize the signs of BVD in their herds.
During the recent National Institute for Animal Agriculture (NIAA) conference in Indianapolis, Stout presented to the NIAA Bovine Committee, discussing Kentucky’s efforts to control BVD.
Stout says 60 to 80 percent of cattle in Kentucky probably are exposed to BVD at some time, with huge impacts on productivity and the state’s agricultural economy. Many of those exposures result in transient, or temporary infection in cows, but BVD exposure also suppresses immunity and is a leading cause of bovine respiratory disease in stocker and feeder cattle.
Many of those infections occur as a result of persistently infected (PI) calves, which shed the virus constantly, being shipped from farms and ranches. PI calves occur when the gestating cow is exposed to the BVD virus during gestation, generally between days 30 and 110 of pregnancy, and becomes transiently infected. Her calf, if it survives, will be PI at birth and can spread the virus within the cow herd, leading to reduced calving rates, and among other calves it encounters later as it moves through the marketing, backgrounding and finishing stages. Stout says transient infections of the dam account for about 90 percent of PI calves, with the other 10 percent resulting from a PI cow, which will pass the infection on to all her calves.
Diagnostic testing can identify PI animals for culling and isolation. PI animals should be removed from the marketing chain, either by euthanasia, shipping directly to slaughter or being finished in a quarantined facility away from other cattle. But, as the committee heard, some producers have knowingly sold and shipped PI calves without disclosing their disease status.
Kentucky, Stout says, is different from most states in that BVD is a reportable disease, meaning producers, veterinarians and diagnostic labs in the state are obligated to report positive results to the state Department of Agriculture. Also, Kentucky has had a law in place for years that forbids sale and transport of animals with communicable diseases. Although the law was created in response to other diseases such as Brucellosis and Tuberculosis, the state’s animal health officials have applied it to BVD as well.
Stout notes that producers who find a PI animal can obtain a permit from the State Veterinarian’s office to ship the animal directly to slaughter, which provides an option for recovering some of its value. This program, he says, should transmission of BVD, but more education and control steps are critical. Stout says he would like to see more targeted education at the cow-calf level, to make producers aware of the economic losses the disease causes in the form embryonic death, abortions and low calving rates. He also would like to see a system for permanently identifying PI animals such as with brands, and for documenting all their movement. He also says greater incentives for testing and perhaps an indemnity fund to reimburse producers who properly dispose of PI animals could provide long-term benefits in BVD control.