Methods of identifying and inseminating nonpregnant beef females after synchronization of second estrus with norgestomet implants

Beef females (547) were included in three experiments to evaluate methods of identifying and inseminating nonpregnant beef females after synchronization of second estrus with norgestomet implants. In the first experiment, heifers not pregnant to the first insemination were identified for insemination via estrus (inseminated via the a.m./p.m. rule or 48 h after implant removal). In the second experiment, females not pregnant to the first insemination were identified for insemination via estrus (inseminated via the a.m./p.m. rule) or progesterone concentrations < 1.5 ng/mL at implant removal (inseminated 48 h after implant removal). In the third experiment, heifers not pregnant to the first insemination were identified for insemination via progesterone concentrations (as in experiment 2) or anterior vagina electrical resistance values < 81 ohm resistance 48 h after implant removal (inseminated after resistance measured). All methods of identifying and inseminating nonpregnant females were equally effective (P > 0.10) and did not effect (P > 0.10) calving rates from the first and second AI.