Timing, Product Choice Critical for Fall Parasite Control

By Sarah Hill for Tri-State Livestock News

The weather is finally getting cooler. It’s time for football, pumpkins, and parasite control. When cow-calf pairs are processed for weaning and pregnancy checks, many cattle producers take advantage of the opportunity to treat cattle and calves for internal parasites.

“Sometimes, when a cow-calf herd comes off summer pasture, you can tell if young calves have picked up parasite issues during summer grazing,” says Grant Dewell, Associate Professor, Vet Diagnostic & Production Animal/Veterinary Preventive Medicine, Iowa State University. “Older cows seem to develop an immunity to internal parasites, but younger cows and calves don’t have that.”

Deworming weaned calves and younger cows is the best form of control for those internal parasites, according to Dewell. It’s up to cattlemen whether older cows are dewormed.

“Some people want to control those parasites, while others get away with not doing it to be more economical,” he says.

Brett Henderson, a commercial cow-calf producer based near Lodgepole, S.D., has opted to treat all his herd—including bulls—with an Ivermectin pour-on after a hard frost in October.

“For calves and any purchased cattle, we’ve used Dectomax injectables in the past. Dectomax is not cheap, but we like it for calves,” Henderson says. “Recently, I’ve been talking with my vet about Valcor from Zoetis.”

Valcor is a combination dewormer combining Dectomax and Tramisol, a dewormer that was very commonly used with sheep, into one dose. According to Dewell, Valcor has two different modes of action, as the Tramisol paralyzes the adult worms already attached to the intestinal wall, causing them to detach and then be defecated out, while Dectomax protects cattle against new exposures with its efficacy on the larval stages of worms and helps kill adult worms.

“Tramisol hasn’t been used much in the last 20 years, so the resistance level is low,” Dewell adds. “It’s a good product, but we haven’t seen much data on it yet.”

As temperatures cool down, flies are becoming less of an issue. Lice is the major external parasite for the winter season, and Dewell says he’s seen more lice problems in the last five years, especially in January and February.

“Some producers may be worried about lice developing resistance to pour-ons, but it’s more a matter of the timing of treatment,” Dewell says. “A lot of times, when treating with pyrethroid products, if cattle are treated earlier in the fall when temperatures are warmer, the lice are dormant, so the product isn’t absorbed. When the weather turns cold and the lice come out of dormancy, the pyrethroid is gone, so it’s not doing much good.”

Although it’s convenient to check for pregnancies and conduct parasite control measures at the same time, Dewell says it’s better to wait for consistent cold weather to treat cattle for lice.

Henderson says he’s had good luck using a product with 3% diflubenzuron, 5% permethrin, and petroleum distillate for lice treatment, and it isn’t overly expensive. The product he likes can help control biting lice, sucking lice, houseflies, stable flies, horse flies, black flies, horn flies, deer flies, face flies, and cattle ticks.

Beef producers in the Upper Midwest don’t need to worry as much about parasites developing resistance, according to Dewell, because dewormers aren’t used excessively in this region. For example, cattle producers in the Southeast use dewormers year-round, so their risk of developing resistance is much higher in that region.

Cattle producers often combine parasite control with another event like preg checking or weaning. Carrie Stadheim | for Tri-State Livestock News