Evaluation of postweaning performance and reproductive measurements in fall-born replacement beef heifers treated with different anthelmintic regimens

Objective The United States cattle industry suffers substantial monetary losses due to gastrointestinal parasites. There are limited data on extended-release and pour-on anthelmintic treatment on growth and reproductive performance in replacement beef cattle. This study aimed to investigate anthelmintic therapy on postweaning growth performance and reproductive success in fall-born, crossbred replacement heifers. Materials and Methods Eighty-three, newly weaned, Angus crossbred, fall-born heifer calves were stratified by BW at d −14, fecal egg count, and day of age and allocated randomly to 1 of 3 anthelmintic treatments: (1) control, no anthelmintic (n = 28; CON); (2) combination pour-on moxidectin and oxfendazole (n = 28; MO); or (3) extended-release eprinomectin (n = 27; ERE). Heifers grazed within treatment groups on separate pastures for a 274-d period. Respective anthelmintics were administered on d 0 and 154. Body weights, BCS, and calf BW were analyzed using the MIXED procedure of SAS. Heifer cyclicity, estrous detection (using an Estrotect patch), AI conception, natural service conception, overall pregnancy rates, and live calving rates were analyzed using the GENMOD procedure of SAS. Significance was declared at P ≤ 0.05. Results and Discussion Final heifer BW, ADG and BCS were greater (P Implications and Applications The inclusion of an anthelmintic increased growth and improved reproductive performance in fall-born heifers over a 274-d grazing study.