“We don't get the winterkill they see up north,” Huston says. “So it's especially important that we deworm in the spring to reduce pasture contamination. A lot of folks are fall calving down here, so they do it when they work the calves or pregnancy check the cows.”

She recommends deworming the cows at turnout or when they're moved to a new pasture. Then, if flukes are a concern, hit the cows again in late summer or early fall with a flukicide, as well as deworming the spring calves at weaning.

Regardless of where you live, it's important to involve your vet as you consider your deworming strategy, Hildreth says. “Every producer has a unique situation and they have to look at their own operation and what they're trying to accomplish.”

Those goals will vary, of course, but for most producers, the goal of profitability is pretty important.

“I think of cows as grass combines,” Hildreth says. “They harvest grass. So having worms is a little like having a bad blade in your combine. It's decreasing the efficiency of that combine and the system isn't working at its optimal level.”