The Impact of Nuisance Flies on Growing Dairy Heifers

Abstract

The horn fly is an economically important external parasite of cows and horses. Cows with large numbers of flies on them have lower milk production and decreased feed conversion due to avoidance activity. These flies are not only a pest; they are also a vector for disease. Many commercial pesticides have lost efficacy in controlling horn flies. This increase in resistance and growing concern regarding food safety issues has prompted investigation into alternate methods of control. In this study, two groups of Holstein-Friesian heifers were observed for their level of horn fly infestation. The pedigrees and microbiomes of the cows with the five highest and five lowest levels of fly infestation were compared. Pedigree analysis showed that some of the heifers with low fly infestation had similar ancestors.  Microbiome samples were obtained from three sites and the results are still being analyzed.