Posted: December 2, 2022

Horn fly resistance observed in Holstein cattle.

Credit: Bailey Basiel

Credit: Bailey Basiel

Some Holstein dairy cattle, particularly those with white coat coloration, naturally fend off the horn fly, a parasitic insect known to cause stress and disease in grazing cattle, according to new research conducted in the college.

The findings eventually could help organic producers whose livestock must be pasture-raised and must not be exposed to synthetic pesticides or given antibiotics, noted lead researcher Bailey Basiel, a graduate student in the Department of Animal Science.

Working with 13 organic dairy producers across the country, Basiel and her team documented fly loads on more than 1,600 pastured Holstein between May and September--the height of horn fly season--from 2017 to 2019. The researchers also performed genetic testing on a random subset of the animals.

The scientists discovered that a region on chromosome 6 was associated with the most variation in horn fly load. The gene KIT, which is involved in coat pattern and coloration, is located within that region and likely is associated with variation in fly load.

--Amy Duke