Lice Management for Beef Cattle

Megan Van Emon, Extension Beef Cattle Specialist

Be on the lookout for lice this year. As our temperatures start to drop, lice may become an issue on your cows, bulls, and calves. These lice feed on blood (sucking lice) or skin and hair (chewing/biting lice). Lice infestations typically occur on beef cattle that are stressed from the cold weather, inadequate nutrition, have internal parasite infestations, or have lowered immune systems.

Heavy lice infestations can result in reduced feed efficiency, milk production, and weight gains. Additionally, these lice infestations can lead to anemia, skin infections, and other diseases. Aside from the treatment cost, due to the scratching and rubbing, facility repairs also play a major economical role in lice infestations.

Adult lice are between 1/16 and 1/8 inches long and spend their entire life on the host. The louse life cycle is approximately 3-4 weeks. Lice are spread throughout the herd by direct contact. Therefore, make sure that you do not have treated cattle next to untreated cattle, this can lead to reinfection of the treated cattle.

In Montana we have four predominant species of lice on cattle, one chewing and three sucking. The cattle biting louse is the most common species found on cattle in Montana and this louse feeds on skin, scurf, and hair. This louse is typically found along the back, withers, poll, and tail head areas. The three sucking lice are the longnosed, little blue, and shortnosed lice. Longnosed lice more frequently infests calves and are located along the shoulders, back, neck, and dewlap. The little blue louse is usually located around the face and will give the animal a bluish tint, which becomes obvious on white-faced cattle. The shortnosed louse is the least common species and the largest. Shortnosed lice are typically found on the neck, brisket, and dewlap.

Several methods may be used to provide lice management, backrubbers, dust bags, pour-ons, and injectables. It is important to note that injectables are only labeled for control of sucking lice. Backrubbers and dust bags should be located in areas where they must be used daily, this will provide better control of the lice. Additionally, both backrubbers and dust bags should be checked weekly to determine if they need to be recharged with fresh insecticide. Pour-ons are applied down the mid-line of the back and the most popular control method. Care should be taken to ensure the proper dose is provided to each animal per label instructions.

There are three insecticides commonly used for lice control, pyrethroids, avermectins, and spinosad. Pyrethroids commonly include piperonyl butoxide which increases the activity of the insecticide. Pour-ons that use pyrethroids are non-systemic, don’t kill louse eggs, and require two applications, 14 days apart. Avermectin pour-ons are systemic, typically cost more, and also control several internal parasites. Avermectin pour-ons also require withdrawal times prior to slaughter. Spinosad pour-ons are non-systemic and requires two applications, 45-60 days apart.

There are several methods and products available for lice control in beef cattle. Make sure to read the labels of the products to determine the species that are affected, dosage required, and for any withdrawal times. One key aspect of insecticide use for lice control is to alter the active ingredient each year. By alternating the active ingredient each year, you will reduce the chances of breeding resistance into the lice populations. I suggest using a 2 to 3 year rotation of active ingredients to help reduce resistance.