Treatment Challenges

The Decision to Treat with Antibiotics is No Longer Automatic

Pathogen resistance to some antibiotics is a concern, especially with respiratory illnesses. (DTN/Progressive Farmer photo by Gregg Hillyer)

Don't write off talk of antibiotic resistance in livestock. It's a real thing, says Mike Apley, a veterinarian with K-State's College of Veterinary Medicine.

"The last time a new family of antibiotics was introduced in food animals was in 1978," he says. "We've had new members of those families since then, but we are probably not going to get more."

Apley reports there are about 10 drugs available today, that are used to treat animals and not people. One class, the ionophores, are livestock focused.

Many of today's concerns around resistance focus on respiratory pathogens, where it has been a common practice to give long-acting treatments. Typically, Apley explains, 70% to 80% of animals treated in these cases will respond. They should get a 5-to-7-day interval to show that response. But in calves, it's possible to see a 5% to 10% death loss.

Producers are advised to evaluate the overall herd sickness level, and if a large percentage of calves are sick reassess treatment protocol. Consider two factors when looking at a possible disease outbreak.

"First is the treatment success rate," says Apley. "The second is the case fatality rate." This makes it extremely important that producers keep good records of treatments given to the herd. That means the date treated, a description of the animal, product used and dosage.

Brad White, also a veterinarian at K-State, adds: "It's easy to want to switch drugs when I feel that things aren't going well. However, if I start changing drugs frequently, that will impact my ability to accurately evaluate those records."

He recommends producers have a treatment protocol in place, to be sure they are using antibiotics appropriately. Understand what you are treating, he says, and understand why you are treating it.

That can be especially challenging with something like scours. The cause is often viral or parasitic. This means antibiotic use is probably not justified.

Bob Larson, K-State veterinarian, explains, the virus however can lead to a bacterial infection.

"The virus damages the gut wall so that the calf is more likely to have a secondary infection in the bloodstream due to bacteria that is commonly found in the gut," he says.

Apley notes about 30% of calves with scours will end up with bacteria in their blood.

"An antibiotic might be part of the treatment," he says. "But if the calves are lying flat then there are hydration and blood acid/base problems and those calves will need intravenous fluids. The antibiotic alone will not be sufficient."

It is essential producers work with their herd veterinarians to make sure they have the right diagnosis, and know what pathogen they are dealing with.

Apley adds, "If you have a history of cases that aren't responding well then it is time to do further testing to isolate the pathogen in the lab and match it to the appropriate treatment."

(CC/AG)