Haematobia irritans parasitism of F1 yak × beef cattle ( Bos grunniens × Bos taurus ) hybrids

The horn fly Haematobia irritans (Diptera: Muscidae) is a blood obligate ectoparasite of bovids that causes annual losses to the U.S. beef cattle industry of over US$1.75 billion. Climate warming, the anthropogenic dispersion of bovids and the cross-breeding of beef cattle with other bovid species may facilitate novel horn fly-host interactions. In particular, hybridizing yaks [Bos grunniens (Artiodactyla: Bovidae)] with beef cows (Bos taurus) for heterosis and carcass improvements may increase the exposure of yak x beef hybrids to horn flies. The present paper reports on the collection of digital images of commingled beef heifers (n = 12) and F1 yak x beef hybrid bovids (heifers, n = 7; steers, n = 5) near Laramie, Wyoming ( approximately 2200 m a.s.l.) in 2018. The total numbers of horn flies on beef heifers and F1 yak x beef heifers [mean +/- standard error (SE): 88 +/- 13 and 70 +/- 17, respectively] did not differ significantly; however, F1 yak x beef steers had greater total horn fly abundance (mean +/- SE: 159 +/- 39) than female bovids. The present report of this experiment is the first such report in the literature and suggests that F1 yak x beef bovids are as susceptible as cattle to horn fly parasitism. Therefore, similar monitoring and treatment practices should be adopted by veterinarians, entomologists and producers.