When calves enter the winter months, you may notice them exhibiting itching, scratching or rubbing behaviors.

The culprit is almost surely lice, says Jerry Bertoldo, a veterinarian and Northwest New York Dairy Specialist for Cornell University.

“Lice are the forgotten winter parasite,” he says. “They tend to ‘bloom’ during the initial surge of cold weather.”

Left untreated, lice can be extremely damaging to the health and productivity of young calves. “Sucking lice can cause anemia quickly in young calves. One bug can remove .10 mL of blood per day, and it’s common for more than 1,000 lice infesting one animal.”

Lice are often acquired by young calves from older animals, and are less of a problem when young animals are segregated from older herd mates. Visual diagnosis of lice is challenging because they are so tiny. Some easily blend into the skin and hair coat, and they don’t hop around like fleas.

For control, Bertoldo recommends anthelmintic treated with a labeled dose of one of the older, alcohol-based pour-ons that are commercially available. Other ectoparasite products also may be useful. Consult with your veterinarian for the best treatment approach for your herd. 

Note: This story appears in the January 2017 issue of Dairy Herd Management.