Diseases can result in abortions, decreasing revenues for cattle producersWritten by Saige Albert
Kansas State University Veterinarian Bob Larson says, “If my cows are working and my bulls are working, if we run into a disease that kills pregnancies, that will kill our momentum, as well.”
Live calves bring revenue to the farm and ranch, and he notes that diseases like infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea can cause abortions and decrease profits for producers.
“IBR and BVD are two of the most common causes of abortion that we deal with,” Larson comments. “The good news is, we have effective vaccines for both of those diseases.”
“IBR is a herpes virus,” Larson says. “That means it is a really common disease, and it is secreted by any fluids. It is easily passed from one cow to the next.”
IBR also results in a lifelong infection in the animal. Infected animals will likely exhibit symptoms, such as a cough or runny eyes, the first time they are exposed. However, from that point forward, they will shed the virus during times of stress.
“They stop shedding the virus until they get stressed,” Larson explains. “If they get stressed during calving, while being moved or whatever, she’ll shed the virus and spread it around for a while.”
In feedlots, the disease is often called red nose.
“It is a really, really common virus,” Larson emphasizes.
While IBR is common, Larson notes that is can be a challenge because it presents mildly in adult cattle.
“They don’t get sick,” he says. “The calves go through it and get runny eye, and abortions don’t happen. They wait about two months.”
He also notes that signs in cows are very subtle.
“We may not see any signs or if we notice problems, we don’t think about them until two months later when the cows start slipping calves,” he says. “This is one of the problems. IBR causes problems.”
Larson further mentions that IBR is one of the major causes of abortion in the U.S. during the last half of gestation.
For producers who start seeing abortions and then remember having runny-eyed calves from the previous year, Larson says, “That makes me suspicious we have IBR.”
Necropsy and sending samples to the lab will confirm the disease.
Larson also notes, however, that vaccines for IBR and prevalent and effective.
“I like to give two modified live vaccines at weaning and breeding to try to set up some good immunity prior to the first breeding season,” he says. “Technically we shouldn’t need more than one, but there is value in making sure as many heifers respond as well as possible.”
He also notes that he prefers to vaccinate replacement heifers at the start of breeding and at preg-check time.
“I have a lot of tips, and I booster my cows once a year,” he says. “Producers should talk to their vet about their preference.”
He adds, “The one concern is that if I give a modified live vaccine to a pregnant cow that is naïve, I can abort her with the vaccine. However, most cows get vaccine or are naturally exposed, so a booster is not enough to cause them to abort.”
“They do need to be well vaccinated before they get pregnant,” Larson says.
“BVD is somewhat similar to IBR in that is it really common, but while there are a lot of cows persistently infected with IBR, only a very few calves carry the BVD virus,” Larson explains, noting that only four to six BVD persistently infected (PI) calves are expected for every 1,000 head that enter the feedlot. “The problem is, if cows aren’t spread out, a couple PI calves can come into contact with a lot of cows.”
He adds, that PI calves shed the BVD virus continually throughout their life, rather than only during times of stress, like with IBR.
“It doesn’t take much contact to get BVD,” he adds.
“If a cow is exposed to the virus during the first half of her pregnancy, one of two things will happen,” Larson says. “Either she’ll abort – and a lot of time she does, but if she doesn’t, the calf will get infected with BVD. If he survives, he will become PI with the virus.”
The source of the BVD virus is nearly always a PI calf. While some PI calves are poor-doing, others look healthy and stay in the herd.
“Our best estimate is about half of the PI calves die between birth and weaning,” he says. “Another half die between weaning and yearling age.”
Often BVD PI calves don’t make it to their first calf.
“It’s a common problem,” Larson says. “If she survives to have her first calf, it will always be a PI calf.”
With BVD, Larson says, “Pregnant cows exposed to BVD will either abort or create new PI calves for next year.”
While vaccines for BVD are available, Larson notes that no vaccine is perfect.
“If they were perfect, we wouldn’t talk about this disease,” he says. “However, if people have an abortion storm, I get to investigate it, and in all my years of looking at problems we trace back to BVD, they are almost always unvaccinated or poorly vaccinated herds.”
He also notes that it is important to follow vaccine protocols and to have a consistent program.
“If we only vaccinate some years or we don’t vaccinate at all, the immunity isn’t the same,” he says.
“Viral diseases are bad,” Larson comments. “They will always cause us some problems, but we have tools that make disease control possible.”
Larson spoke during a producer dinner in early March in Gillette. Boehringer Ingelheim Vetmedica sponsored the dinner.