With over 1.3 million calves born in Saskatchewan each year, producers need to be conscious of vaccinating their herds against bovine viral diarrhoea... or B.V.D.
The virus, which can manifest in various clinical syndromes, can result in serious losses to producers with infected herds.
“It can cause some major problems: either abortions or calf mortality or infertility,” said Dr. John Campbell, a professor at the Western College of Veterinary Medicine. “A number of different scenarios can happen from it, so it’s not something you want to get in your herd.”
With calving season nearly complete, Dr. Campbell advises that now is the time to plan for BVD vaccination.
“We need to protect the cow for next year’s pregnancy in order to protect the foetus she’ll be carrying. So, we vaccinate the cow to ensure she’s safeguarded, and at the same time we protect the foetus that she has next year,” he said.
Dr. Campbell says that the prime time for vaccination is three to four weeks prior to breeding, before cows go to pasture, unless the producer is calving on pasture, in which case the timing is a bit later.
“The first choice you have to make is between a killed or modified-live vaccine,” he stated. “In most cases, the modified-live vaccine provides much better protection, and usually has label claims for protecting the foetus. We would recommend the modified-live vaccine in just about every situation. There are a variety of companies that all make very good
vaccines.”
Dr. Campbell says he is aware that some producers have difficulty getting vaccinations done when calves are young and cows must be separated from them.
“Some will say I’ll just give them a killed vaccine in the fall, because I’m handling the cows then and that’s pregnancy-checking time,” he noted. “The trouble with that approach is the killed vaccine is being relied on to maintain its effect from fall until the next breeding season, and it is not nearly as effective as a live vaccine.”
Dr. Campbell notes that there are now some vaccine companies with label claims that suggest a live vaccine can be used on pregnant cows very late in gestation. He warns that this approach is only effective if the cow has been previously vaccinated with the same vaccine. If not, she may abort.
When considering different approaches to vaccination for BVD, Dr. Campbell advises producers to consult with their local veterinarians to discuss their specific herd management practices and to ensure the most effective method is used.
He also stresses that vaccination is important, even if a herd is already infected with BVD.
“If there’s a cow walking around unvaccinated in the pasture in early pregnancy and she gets infected, she may not get very sick, but the virus infects her foetus,” Dr. Campbell said.
“If that happens at a certain time of gestation, it can cause abortions or congenital abnormalities, or can cause the new calf to become persistently infected. Those calves are often the source of a BVD outbreak.”
Dr. Campbell advises that if you have BVD in your herd, you must vaccinate to make sure you don’t get a broader outbreak the following year. He says the producer must try to find the persistently infected calves and get them out of the herd. Veterinarians have a relatively simple test to identify the BVD carriers.
Source: Saskatchewan Agriculture and Food website at www.agr.gov.sk.ca.