Date of Graduation


Document Type


Degree Name

Bachelor of Science

Degree Level



Animal Science


Yazwinski, Tom A.

Committee Member/Reader

Tucker, Chris A.

Committee Member/Second Reader

Powell, Jeremy G.

Committee Member/Third Reader

Rorie, Rick

Committee Member/Fourth Reader

Rosenkrans, Charles


The purpose of this study was to evaluate the efficacy of extended-release eprinomectin against horn flies, face flies, and fecal egg counts of parasitic nematodes in crossbreed replacement beef heifers. Fifty-four heifers were randomly placed into three treatment groups (N=18 heifers/treatment). Group 1 was administered the labeled dosage of extended-release eprinomectin on day 0. Group 2 acted as the negative control. Group 3 received the anthelmintic injection once a quarter of the heifers in the group reached the threshold treatment level for horn flies (N=200 flies/animal; day 41). Nematode infections were measured via fecal egg counts while horn and face flies were visually monitored. Evaluation of pregnancy status was recorded at study conclusion (day 144). Due to the high number of face flies, heifers were treated with insecticide dusts twice during the study (day 54 and 69). Low egg counts for all treatment groups reflected minimal parasite burden. Extended-release eprinomectin had little influence on face flies given that all groups were above threshold at days 40, 48, and 54. At study conclusion, horn fly population was lower (PP


extended-release eprinomectin, anthelmintic, fecal egg counts, horn flies, face flies, heifers