Getting rid of this scoundrel of the cowherd is doable…but it takes persistence and a plan
By Rhonda McCurry
Photos by Tim O’Byrne
There are numerous diseases and health issues that can impact profitability in a cow herd. One that can sneak up on a rancher without warning and cause big-time economic problems is Bovine Viral Diarrhea, or BVD.
BVD is a viral disease that is known to cause infertility in a herd and have other reaching effects on cows including pneumonia, abortions, still births, weak or deformed calves and immunosuppression. It can also impact calves, lowering their immune systems, making them susceptible to pneumonia and diarrhea. Bottom line is that this complicated disease can be managed and in order to do so, eradication of BVD should be a goal in every cow herd across the country.
Dr. Summer Hansen, veterinarian at Powder River Veterinary Hospital and Supply, Kaycee, Wyoming, says BVD is not obvious. A rancher may see clinical signs of diarrhea, or the herd might have a subclinical infection with no visible signs. When a bred cow is infected early in gestation the disease will be transmitted to the fetus, which can cause early embryonic death. Depending on time of gestation when infection occurs the result can be, stillbirths, deformities or persistently infected calves. Persistently infected (PI) calves develop when the fetus is developing the lymphatic and the immune system. An infected calf will never build antibodies to the virus and is likely to appear normal at birth.
Dr. Hansen says, in contrast, calves can also be born smaller in size and be poor-doers. The biggest problem, she explains, is that the calf might be born “normal” then shed the virus like crazy, thus infecting the herd. Transmission occurs through bodily fluids like urine, feces, milk and semen. It is most detrimental during 120-150 days gestation, when it can result in PI calves shedding mass amounts of the virus.
Not one, but two!
There are two types of BVD. Dr. Hansen says if a cow is infected with both types the result is a mucosal disease appearance, which looks similar to other diseases like foot and mouth or vesicular stomatitis. She says a veterinarian must pull blood and test for the specific disease to be sure. A questionable animal should be quarantined until the results are known. It is recommended if one calf tests positive for BVD the remaining calf crop should also be tested to find any PI calves.
“If you have a cow positive for BVD, the chance of her being the only one is not great,” Dr. Hansen says. “I recommend people test to find others that might be infected to make sure it’s not going to continue through the herd and cause problems.”
Cows and calves can be tested two ways; by blood test or an ear notch. If a calf/cow has a high level of BVD then a re-test should be administered two weeks later to determine if it is a transient infection or if it is a PI. Dr. Hansen says a rancher should look for clinical signs, then begin testing to pinpoint the problem animals. It is recommended that any new cows or bulls being brought into the herd should be tested.
Testing a herd bull is also important to be sure they are not spreading BVD, too. Though the disease does not directly impact bull fertility the males can pass it on during breeding season. Dr. Hansen says if it has been a problem in the herd to build a budget for the test each year. It can be done at the same time a rancher tests for semen vitality, then continue to test the herd every few years.
Avoiding the disease is only possible if a rancher has a closed herd, which is difficult to accomplish. Dr. Hansen says quarantining and testing new animals is the key.
“You’ll always have the neighbor’s bull over the fence or a stray pair, but try not to just pick up new cows at the sale barn, come home and turn them out,” recommends Dr. Hansen.
Good news
The good news is that there are vaccines available to manage BVD. Talk to your veterinarian to find out what’s best for your herd or area. Annual vaccines are important because even an older cow can get a subclinical infection and possibly transmit BVD. In Dr. Hansen’s area bacterial pneumonia has become a big issue in the fall, so she recommends her rancher clients give a BVD vaccine plus pasteurella. As with any virus, Hansen says even if BVD is not causing overt clinical signs the disease is going to cause stress and leave the animal open to other infections.
“For example, if you’re having trouble with cows getting pneumonia in the fall it could be your herd is fighting a virus, putting stress on its immune system,” Dr. Hansen explains. “You might not see BVD itself, but it may open the door for another virus to take hold.”
BVD is a constant for American cattle ranchers.
“It’s always been around,” she reminds. “It’s a constant thing you need to keep in the back of your mind.”
