EFFECT OF POSTPARTUM BULL EXPOSURE ON CALVING INTERVAL OF 1ST-CALF HEIFERS BRED BY NATURAL SERVICE

Ninety-four first calf heifers were utilized to evaluate the effect of bull exposure on the calving interval. Heifers were alternately assig ned after calving to a pasture containing epididymectomized bulls for 60 d or were not exposed. Thirty-five days prior to the breeding seaso n the bulls were removed and the two groups co-mingled. Bull-exposed h eifers had a 9-d increase in calving interval and a 7-d delay in avera ge calving date compared to unexposed heifers (P < 0.05). Bull exposur e early postpartum did not shorten the calving interval of heifers in condition score of 5 or better at calving and bred by natural service under the conditions of this study.