UW research targets horn fly scourge variables

Cow having ulstrasound
Craig Calkins enters data from cattle at the Laramie Research and Extension Center.


Two cows. Same University of Wyoming McGuire Ranch pasture northeast of Laramie near Sybille Canyon.

One cow has 383 horn flies sucking her blood; the other cow has four.

Why that remarkable difference?

Cody High School graduate turned veterinarian, turned Army major, and now a Ph.D. student at the University of Wyoming, Craig Calkins is helping UW Extension range specialist Derek Scasta unravel the mystery of a pestilence that costs the livestock industry billions of dollars in losses.

Calkins is eyeing whether shorter blood clotting times of individual animals clogs a fly’s attempts, whether a thicker hide frustrates flies, and if elevation and environmental conditions, such as colder and wetter areas, affect fly parasitism.

Considered a filth fly, horn flies (Haematobia irritans) feast on a cow’s blood, leave to lay their eggs in manure, then fly back to their beef buffet. Eggs hatch after about two weeks, and a new generation begins.

The flies pierce the hide and inject an anti-coagulant to help free the flow of blood. Cattle swing their heads, slap their tails and twitch their skin in attempts to stop the biting.






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