“There are about nine different parasites that cause problems, but Ostertagia ostertagi — or the brown stomach worm — is the No. 1 most damaging internal parasite in cattle,” Sides says. “In the most severe cases, Ostertagia ostertagi can inhibit feed intake, meaning cattle don’t gain like they should and can’t fight off other health issues as easily.”

Because the brown stomach worm, and other stomach worms, are bloodsuckers, they cause irritation and inflammation to the stomach and intestinal linings of cattle. As a result of inflamed or irritated stomach lining caused by parasites, infected cattle can’t properly absorb nutrients as they normally would.

In fact, research has shown that the brown stomach worm and other parasites could cost the industry up to $3 billion annually in lost weight gains, poor feed conversion and increased disease.

“Especially with calves, if you don’t deworm, the response can be the same as non-implanted cattle — you can give up that many pounds,” Sides says. “If you don’t deworm while the calves are on grass, then you give up subsequent feedlot performance. You can see poorer dressing percent, lower quality grade, and all just because of the parasite infection while the cattle are on grass. Even if they’re dewormed later at the feedlot, it’s too late to make up for the lost growth potential.”

Dr. Sides recommends producers deworm cattle in the spring to help protect against Ostertagia ostertagi and other parasites that can potentially rob cattle of performance and producers of profits.

“Injectables really do the best job on internal parasites, but lice control is better with pour-ons,” Sides says. “With the producers I talk to, I tend not to be as concerned with the external parasites. I would rather kill the internal parasites that can do the most to slow down growth and feed efficiency.”