Some producers have begun vaccinating calves at turnout, or are adding respiratory vaccines to branding-time protocols. This may help, depending on the age of the calves and the products used, the researchers say. Success may depend on whether the calves are old enough that their immune systems can respond to vaccination, since maternal antibodies from colostrum may interfere.

“Some research suggests that calves 60 to 90 days of age can respond to vaccination. In some instances, they do; sometimes, they don’t,” Woolums says.

Calf age at branding can vary greatly. The oldest might be 2 to 3 months old, while the youngest might be only a week old.

“A week-old calf isn’t likely to respond adequately to vaccination. A dairy calf that received no colostrum can respond to vaccine at a week of age, but a beef calf that received good colostrum won’t reliably respond. So it depends on the proportion of the herd that is 1 to 2 weeks old, vs. the proportion that might be 2 to 3 months old. If the proportion of really young calves is small, it may not be a problem,” Woolums explains.

Age at vaccination is an important aspect. “The other piece of that challenge is that even if you know when to vaccinate, you need effective vaccines against the pathogen that’s involved, or you’re just shooting in the dark,” Smith says.

Ranchers should work with their herd-health veterinarian to design a specific strategy for their operation. No one formula or schedule fits all herds, Woolums says. 

Regardless of when you vaccinate, and with what, some calves won’t mount adequate immunity for one reason or another. “There is also a genetic component — not just in resistance to bovine respiratory disease, but also in response to vaccination,” Woolums says. 

The challenge of sampling

Woolums would like to have a student sample calves when ranchers gather a herd for artificial insemination.

“Then later, if some calves get sick, we could sample them again and see if there’s a difference. One reason there isn’t more research on summer pneumonia is because it’s hard to sample the calves,” she says.

Beef calves aren’t conducive to sampling, except at branding. Calves could be captured during an artificial insemination (AI) program, but not all producers use AI.

“It’s also hard to sample them without changing the risk factors. If we bring them all in to sample them, we’ve grouped them in a situation where they wouldn’t ordinarily have been grouped,” she says. This creates even more risk factors — stress of handling and commingling in close quarters.