Master of Science (MS)


School of Animal Science

Document Type



One of the most significant threats to the well-being and performance of grazing livestock are gastrointestinal nematode (GIN) parasitic infections. Allowing a large GIN burden to manifest can cause a significant cost in terms of productivity in grazing cattle. Beef producers commonly rely greatly on the efficacy of broad-spectrum anthelmintics, to not only kill resident worms but to also prevent the establishment of ingested infective stage larvae (L3) for a period following treatment. Eprinomectin (LONGRANGE®, E-LR) is the first extended-release injectable cattle dewormer that claims to provide cattle producers season-long persistent parasite control for 100 to 150 d in a single dose, dependent on parasite species. This in turn, improves nutritional efficiency. The purpose of this study is to evaluate the efficacy of E-LR for controlling long-term GIN infections in nursing calves. E-LR was compared to the traditional anthelmintic fenbendazole (Panacur®, F-P). Four groups of nursing calves (with their dams) grazed separate pastures and pastures were rotated after each sampling date to ensure equal parasitic pasture exposure. Two groups were treated with E-LR and two groups were treated with F-P. Calves were weighed at 28 d intervals and fecal samples were collected on d 0, 14, 28, 56, 84, and 112. Results indicated E-LR was effective in providing long term parasite control. There was no significant (p < 0.05) difference in the FEC between F-P and E-LR treated animals on d 14, showing that both were efficient at initially killing GIN. Significant differences in FEC between treatments started to show by d 56. On d 56, there was an increase in FEC in calves treated with F-P which continued to increase throughout the rest of the study. The E-LR treated animals had only slightly increased FEC for the rest of the study which indicated prolonged GIN control.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Miller, James