This article was originally published in Wisconsin Agriculturist

Most beef farmers are familiar with the onslaught of lice during the winter. It is a common fact that lice populations on cattle peak during the winter months. But what are lice? Lice are small, flat-bodied insects with legs modified for grasping hairs. These creatures are dependent on cattle to survive and can only live off the animal for a few days. Two common species of lice infest our cattle. They are sucking lice and biting lice.  Sucking lice suck blood from the host while biting lice eat skin debris. The female of the species will lay an egg at the base of the cattle’s hair. The eggs are glued individually to hairs and will hatch in about two weeks. When the eggs hatch, the baby lice are called nymphs. The nymphs resemble the adults but are smaller. It takes the nymphs about three weeks to mature into adult lice. The adult lice live for about 2 – 3 weeks, and the females lay about one egg per day¹.

The tell-tale signs that your cattle are suffering from a severe lice infestation are hair loss, raw spots, reduced weight gain, and general thriftiness. While hair loss is not a big deal in the summer months, losing hair in the winter months can result in frostbite. The USDA has estimated that livestock producers lose up to $125 million per year due to the effects of lice infestations. This number includes direct performance losses and wear and tear to facilities². The energy that lice “steal,” coupled with other factors, can have a severe impact on animal health. Therefore, determining the severity of the infection is one of the most important things you can do.

To determine the severity of the infection, count and record the number and species of lice found per square inch of the hide. Sucking lice will tend to stay stationary when disturbed, and they like to cluster together. Biting lice will move when disturbed and do not want to be by other lice, so you will see individuals jumping around. If the infestation is less than ten lice per square inch, then you can consider leaving the lice alone. The economic threshold to treat lice is ten or more lice per square inch of the hide². If you decide to treat it, select a product that will work the best for the population of lice you have present. Sucking lice feed on blood and serum, so they are controlled more effectively with a systemic injectable product. However, biting lice feed on dander, so a systemic product has little effect.  Biting lice are more effectively controlled with a topical treatment³. It is essential to make sure you apply the product as directed to avoid future resistance issues. You should also check the animals several weeks after treatment to make sure the treatment was effective. If you decide not to treat because lice numbers are low or the animals do not seem bothered by the lice infestation keep in mind that the lice populations will begin to decrease in activity as the weather starts to warm.

References:

1. Townsend, Lee. 2000. “Lice on Beef and Dairy Cattle.” University of Kentucky College of Agriculture. https://entomology.ca.uky.edu/ef512. Accessed 1/26/2021.
2. Tarpoff, A.J. “Managing the impact of cattle lice during the winter months.” Kansas State University. https://enewsletters.k-state.edu/beeftips/2018/01/01/managing-the-impact-of-cattle-lice-during-the-winter-months/. Accessed 1/26/2021.
3. Stokka, G., Ueckert, A. 2017. “Lice in cattle a Problem.” North Dakota State University. https://www.ag.ndsu.edu/news/newsreleases/2017/march-6-2017/lice-in-cattle-a-problem. Accessed 1/26/2021.

Reviewed by: Sandra Stuttgen, UW-Madison Extension Taylor County and Bill Halfman, UW-Madison Extension Monroe County