Producers should consider testing for BVD
Hosts of the Kansas State University Beef Cattle Institute (BCI) Cattle Chat podcast Brad White, Dustin Pendell, Bob Larson and Phillip Lancaster discussed several current events and topics related to livestock production, including bovine viral diarrhea (BVD).
“Many of the cattle vaccines we administer, whether it’s a respiratory or reproductive vaccine, include an immunization for BVD,” says the BCI team, noting now might be the best time for cow/calf producers to test for the virus if they think it may appear in their herd.
Though commonly vaccinated for, BVD can cause major implications in any exposed herd. Infected cows can abort their calves or exhibit a lower percentage rate of conception, and the virus can cause ripple effects through young calves.
Vaccinated cows exposed to the virus between approximately 60 and 120 days of pregnancy may still occasionally produce persistently infected carrier calves, according to a 2019 study at Cornell.
Calves may be exposed to the virus as a fetus and born with problems or show symptoms after they’re on the ground. Once infected, calves are more susceptible to scours-causing-organisms and pneumonia come summer.
Uniquely, “BVD can impact all body systems of all ages,” the Cattle Chat team explains. Any one of these symptoms or signs could be reason enough to test for BVD.
Additionally, the virus is unlike many other pathogens in the way it manifests in herds. “The biggest source of the virus are persistently infected calves,” states the team. “Once they are infected, they are infected for life. There are several bacteria and viruses which can cause infection for life, but in those situations, they become infected after they are born.”
Persistently infected (PI) calves become exposed to BVD while they are a fetus, the Cornell study showed. PI calves are carriers of the virus and can shed the virus for its entire life, which can affect other animals.
Pregnant cows, on the other hand, may be exposed and will show little to no signs. The problem after exposure lies with unborn calves and future interactions with calves born to pregnant cows infected with the virus, creating PI individuals.
Testing for the virus
Testing for carriers becomes a helpful tool for producers, because if cattle test negative, they will likely never be infected. Testing slightly before breeding season is a logical solution to potentially eradicate this virus from herds.
“If a producer can find all of the PI calves before the start of breeding season and remove them from the herd, they can remove the big source of the virus,” the BCI team shares.
When deciding whether to test cattle in their herd, one might consider the frequency of BVD.
The team of Extension experts explains, “We have good numbers on how frequently this virus is affecting herds. The virus frequency probably affects a little less than 10 percent of herds, closer to seven percent.”
In their considerations for testing, producers should recall if there have been recent changes in cow fertility rates or odd illnesses in calves. If a producer has suspicions of BVD in their herd, identifying the carriers prior to conception would eliminate exposure to PI calves and increase chances of eliminating the virus altogether.
The team of experts at the Kansas State University BCI suggest certain preparations for producers before completing BVD testing in their herd.
“Have the discussion with the herd veterinariad, and be prepared for how to handle the results of the test if cattle test positive,” they note. “One of the recommended disposition techniques for those calves, if they are PI, is to remove them from the herd and likely know when to euthanize them.”
The team adds, “Don’t sell a PI calf, as they will be shedding the virus for their entire life. So, be prepared for this ascpect.”
Chaney Peterson is a corresponding writer for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.