Dave Sparks knows that anytime two ranchers get together they’re going to talk about the weather first and the market second.

If there’s still coffee in the pot, though, they’re going to get around to vaccination programs before long.

“What do you use? What’s working for you?—That’s what cattlemen want to know,” the Oklahoma State University Extension veterinarian said.

“What we really need to do,” Sparks said, “is change the way we think about vaccination programs.”

The first thing he’d like producers to understand is that immunity is not a black and white issue. It’s not a matter of, if they’re vaccinated they’re protected and if they’re not, they’re not.

Gray areas - that’s what Sparks calls them. Individual animals are different. Levels of disease pressure are different. What it all comes down to, he said, is immunity level versus challenge.

“Most cattlemen have had the experience of a product that worked for a while and then didn’t seem to work anymore,” Sparks said. “Chances are, it wasn’t the product. It really isn’t that black and white. You have calves with different levels of resistance that face different levels of disease.

“A calf exposed to a respiratory disease may be lightly challenged or it could be highly challenged,” Sparks said. “As long as the disease challenge is less than his immunity level, he’ll be all right but when the challenge exceeds his immunity, then you have problems.”

On the “challenge” side, it’s obviously important to do whatever you can to limit exposure to disease.

On the immunity side, Sparks pointed out that a calf’s ability to respond to a disease challenge, along with the efficacy of any vaccine that has been administered, dictates his individual level of immunity.

“One of the things that makes it hard is the complexity of the decision the rancher faces,” Sparks said. “There are more than 150 products and combinations of products for respiratory viruses alone.

“They are all good products. They all work. Their efficacy has to be proven or they don’t get a label. Maximizing the calf’s response to them is probably much more important than which product you use.”

The big question everyone ponders is, which is better, a killed virus vaccine or a modified live?

The killed virus vaccine takes longer to work and doesn’t last as long as the modified live version, Sparks said. It also requires multiple boosters but there is no danger of causing a disease outbreak because the virus is dead. It does, however, cause more stress to the animal because it requires an adjuvant to work. You can’t get immunity without inflammation, he said, and since the virus is dead, an adjuvant is added to cause the required inflammation.

The modified live vaccine produces quicker and longer lasting immunity with little or no booster. The drawback, Sparks said, is that you have to be careful about what class of cattle you administer it to. It can cause abortion in pregnant cows if they haven’t previously had a live viral vaccine. And, if you give it to a calf nursing a cow that has never had live vaccine, the calf can shed enough infection to cause abortion in the cow.