INDUCTION OF PUBERTY AND SUBSEQUENT REPRODUCTIVE-PERFORMANCE

A trial was conducted over 3 years to evaluate the success of inducing puberty in heifers of young age and light weight and to evaluate their subsequent reproductive performance at first calving. The control heifers and the young age heifers were grown at a rate of .56 kg/day compared to .23 kg/day for the light weight heifers. Eleven days prior to the start of breeding, heifers in the young age and light weight groups received the Synchromate B treatment. Implants were removed after 9 days. Average age and weight at breeding were 407, 334 and 406 days and 266, 239 and 243 kg for control, young age and light weight groups, respectively. After a 45-day breeding season 91, 47 and 81% of the heifers in the control, young age and light weight groups, respectively, (P<.05) had been in estrus. Pregnancy rates of the heifers that came into estrus were 67, 7 and 63% for the control, young age and light weight heifers, respectively, (P<.05) at the end of the 45-day breeding season. In the control and light weight groups 95 and 79% (P<.05) of the heifers that were diagnosed pregnant calved. Postpartum interval was 24 days shorter (P<.05) in the light weight heifers suckling calves and calf survival was 16% lower (P<.01) in the light weight group compared to the control heifers. © 1979.