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West: Lice control in the winter

Carmen Willmore for Progressive Cattle Published on 25 January 2022

Does it ever seem that your cows can’t find enough things to scratch on during these long winter months? Constantly rubbing on and breaking gates, posts, boards – if they can use it to scratch themselves on, it’s probably going to break and need replaced soon.

If this is happening at your operation, you probably have a lice problem. During winter months, lice populations can increase due to the animals’ heavy winter coat providing extra insulation from the cold temperatures for the lice.

Symptoms of a lice infestation are hair loss, excessive rubbing of hair off onto fences and other surfaces, and a general unthrifty appearance. To confirm lice is the problem, catch a few head in a chute, part the hair at the topline, withers and face; if you find greater than 10 in a square inch, you have a lice infestation.

It is important to choose a product to best treat the lice affecting your cattle. Consult with your veterinarian on what products work in your area and type of lice affecting your herd. Treatments for cattle fall into four categories: animal sprays, contact pour-on, systemic pour-on (absorbed internally) and systemic injectable. Systemic applications are not advised during the winter months. These treatments can cause a host-parasite reaction, killing developing cattle grubs while they are in the esophagus or spinal canal of the animal, which can cause severe damage. Non-systemic products can be used during the November-to-February time.

Depending on the label directions, some treatments are single applications, while some require two doses given 14 days apart. Non-systemic pyrethroid products are effective against adult lice but not against eggs or larvae; the 14-day window gives those young lice and eggs time to mature, which will then be affected at the adult stage with the second dose. No matter what treatment you choose, you need to ensure you can administer the appropriate dosage for the animal size. Underdosing will not give you the control you need and can lead to reinfestations.

Back rubbers can also be a useful tool if your facilities and management capabilities allow for one. It is important to “reload” the back rubbers based on the number of cattle in the pen or pasture so they are all receiving adequate treatment, again, to make sure cattle are not being underdosed. Managing lice in the winter can be a challenge; if lice infestations are an issue for your herd, consider making plans for the upcoming fall, when management of external parasites is easier prior to population increases.  end mark

Carmen Willmore
  • Carmen Willmore

  • Extension Educator
  • University of Idaho Extension – Lincoln County
  • Email Carmen Willmore