Reproductive performance of 2-year-old Hereford and Angus heifers as influenced by pre- and post-calving energy intake.

p REPARTUM and post-partum energy intake has been shown to influence reproductive performance of beef cows (Wiltbank et al., 1962, 1964). A low level of energy before calving was shown to delay onset of estrus following calving. Marked differences in conception rate were noted in cows on varying levels of energy following calving. Conception rate was decreased by low levels of energy after calving while cows which were full fed after calving had high conception rates. The results of these experiments were promising enough that further investigation seemed warranted. The experiment reported here was designed to determine the effects of two precalving and three post-calving levels of estimated digestible energy intake upon the reproductive performance of 2-yr.-old Hereford and Angus heifers nursing their first calves.