Production and equipment losses are costly to cattlemen. Constant rubbing is a sure-fire sign your livestock may have biting and sucking lice. Late winter, early spring is prime time for lice populations on beef cattle to increase. A few animals may be carriers and actually have lice year-around. This may only be one to two percent of the herd and usually occurs in older cows or bulls, but they can re-infect other animals causing increased populations among all livestock.
Biting lice survive by feeding on the skin, hair and sloughed skin cells of the animal. A complete life cycle of biting lice can occur in as little as three weeks, and adults can live as long as 10 weeks. The adult biting louse has a brownish-amber colored head with a darkly-outlined abdomen with a series of brown crossbars on a pale background. It is commonly found near the base of the tail and along the topline of the animals.
Sucking lice, on the other hand, are a more serious pest that survive by penetrating the skin and feeding on the host’s blood. Generally dark in color, sucking lice are typically found over the shoulders, down the animal’s neck, on the ears, dewlap or brisket. The short-nosed louse can complete its life cycle in about 28 days, however the time may range from three to six weeks.
University of Kentucky Extension Entomologist Lee Townsend says non-systemic insecticides are effective against all types of lice. However, he reports avermectins, moxidectin and eprinomectin, which are systemic products, mainly kill sucking lice.
When using non-systemic products, a second application is usually needed about three weeks after the initial application to kill lice that were in the egg stage during the first treatment. Read the label of the product being used to be sure of correct treatment procedures and note any withdrawal times that need to be followed.