"In any situation where the biosecurity is potentially lower because of mixing cattle from different sources, we have higher risk of infectious disease."
Waldner's research analyzed over 200 herds and 30,000 head of cattle. She was particularly interested in cattle at high risk of disease due to mixing of different herds — including cows placed on community pastures.
"Community pastures bring cattle together from many different herds — increasing the risk of disease transmission. It's similar to what we often see when young children from different families come together in schools or daycares."
The main infectious diseases on the radar for western Canadian producers during pasture and breeding season are IBR, BVDV, trichomoniasis, and bovine general campylobacteriosis (vibriosis), says Waldner.
"When we looked at the cows most likely to be exposed to disease and the impact of vaccination in those animals, it became clear that there is an advantage to vaccinating cows that are going to be mixed with other animals whether it's a community pasture situation, fence-line contact with other high risk herds, or when new animals are purchased into an existing herd."
"While unvaccinated cows on community pasture were more likely to be open in this study, there was no difference between vaccinated cows that were on community pasture and cows that weren't on community pasture whether or not they were vaccinated for BVDV and IBR."
Waldner lists BVDV, IBR, and clostridial vaccine programs as important preventive protocols that should be considered for all cow-calf herds heading to pasture. Other vaccines can also be very important in some areas and producers should annually review their vaccine program with their veterinarian to best protect herd health and cow fertility.
Waldner explains that after considering other factors that affect fertility in her research study, vaccinated cows on community pasture had higher pregnancy rates than unvaccinated animals. She adds that other studies have looked beyond just cows getting pregnant.
"Even if a cow does get pregnant, we want to make sure that she doesn't have a calf persistently infected with BVDV and we want to be sure the cow carries her calf to term," she says. "There are benefits in terms of preventing persistent infection with BVDV and in lower abortion rates for vaccinated cows compared to the unvaccinated cows."
Waldner explains that the key to successful BVDV control programs are to find and remove persistently infected (PI) calves while decreasing the chance that more will be born. "PI calves are the virus factories that maintain the disease in the herd."
Aside from improving fertility, preventing PI calves can also earn producers more dollars in the long run through the potential for higher weaning weights.
"We did another study a few years ago that showed calves that were exposed to persistently infected calves — animals that likely just had a short term or transient infection with BVDV — were up to 15 kilograms lighter at weaning than ones that never had any exposure to BVDV," says Waldner.
"So just being exposed to BVDV could cost you significantly in lost weaning weights."
Waldner is still developing a formal cost-benefit analysis for producers based on her findings. But between the potential for higher pregnancy rates, decreased abortions and higher weaning weights, she says the added revenue from vaccinating cows outweighs the cost of vaccines for many producers.
The WCVM study also compared cows that stayed at home to those that went to community pasture as well as groups that were vaccinated and unvaccinated in both locations.
"While unvaccinated cows on community pasture were more likely to be open in this study, there was no difference between vaccinated cows that were on community pasture and cows that weren't on community pasture whether or not they were vaccinated for BVDV and IBR," Waldner explains.
Waldner advises producers to consult with a veterinarian and determine the best vaccination program and schedule based on their cattle, location and the amount of risk involved. Some risks can be estimated based on how much contact cattle have with other herds.
"The message here is that if your cows are going to be mixed with other herds and are therefore at a higher risk of exposure to infectious disease, there can be real economic benefits to vaccinating."
Rosie Templeton grew up on a Hereford cattle ranch and grain farm near Coaldale, Alberta. She is studying Agricultural Communications and Agribusiness at Oklahoma State University. She can be found on Twitter @rotempleton.