Effects of Administering Progesterone and GnRH Before Puberty on Age at Puberty and Reproductive Response in Crossbred Beef Heifers

One hundred six crossbred heifers were utilized to determine prepubertal treatment of progesterone or progesterone plus Gonadotropin Releasing Hormone (GnRH) on age at puberty, conception to a synchronized estrus and conception during the breeding season. Days to puberty were 369.5 ± 6.2, 363.1 ± 9.9 and 360.4 ± 7.8 or control, progesterone primed and progesterone plus Gonadotropin Releasing Hormone (GnRH), respectively. There was no difference (P\u3e.05) in age of puberty, number cycling before synchronization or conception rate during a 35-day breeding season. The percentage of heifers conceiving to synchronized estrus was lower (P\u3c.10) for control compared to progesterone or progesterone plus GnRH treated heifers. Injecting GnRH at breeding had little (P\u3e.05) effect on increasing conception rates to the synchronized estrus or during the breeding season