Fall is a good time to deworm cows to protect winter performance, and the same applies for calves retained through the winter. Gary Sides, a cattle nutritionist for Pfizer Animal Health based in Sterling, Colo., says internal parasites suppress appetites, limiting nutrient intake and absorption.  In fact, Sides says that producers can lose up to $200 per cow-calf pair through production and reproductive losses due to parasite infection.

According to Sides, parasites require cattle to complete their lifecycle. “The purpose of strategic deworming is to treat cattle in a timely manner to reduce the total parasite load on pasture,” he says. “This reduces total exposure of parasites to all cattle on that pasture.”

Sides recommends deworming in the fall and again in the spring before turnout, with a reputable dewormer. “In a spring-calving herd, the cow and calf should both be dewormed. The stress on a calf’s growth rate and immune system is much higher than that of its dam because it’s not as well developed and has not built up any resistance to parasites,” he adds.

“I like using injectable dewormers in the spring because that’s when you find the highest internal parasite load on pastures,” Sides says. Sides recommends working with your veterinarian to design a parasite-control program that fits your operation.