PSVIII-16 - Effect of Estrous Synchronization with Natural Service or Fixed-Timed Artificial Insemination with Conventional or Gender-Skewed Semen in Beef Females

Reproductive efficiency is critical for profitability, and age at weaning critically impacts weaning weight. The objective was to evaluate estrous synchronization and/or AI with conventional (CON) or gender-skewed (SEXED) semen on calving distribution. Beef females (n=1,620) were either 1) synchronized (7-CIDR:Syn) or not synchronized (Nonsyn) and mated to bulls, 2) synchronized (7-d CIDR) and mated to bulls (SynNS) or artificially inseminated (SynAI), or 3) synchronized (7-d CO-Synch plus CIDR) and AIed with CON or SEXED semen. Calving distribution and gender were determined at birth and were analyzed using the GLIMMIX procedure in SAS. Synchronization resulted in more calves born from d1 to 14 (P < 0.01; 62% vs 47%) of the calving season. There was no differences (P = 0.31) between Syn and Nonsyn in the percent of calves born after d21, but between d22 and 42, more (P = 0.04) calves were born in the Nonsyn group. A greater proportion (P < 0.02; 46% vs 38%) of calves were born in SynNS between d1 and 14 compared to SynAI. There was no difference between treatments (P > 0.12) from d1 to 42, but more calves were born for SynAI after d43. With SEXED semen, there were no differences (P > 0.14) between CON and SEXED for the proportion of calves born from d1 to 14 or d1 to 21; however, more of the desired gender were born in the SEXED group during d1 to 14 of the calving season (P < 0.01; 84% vs 68%). More total calves were born from d22 to 42 in the SEXED group compared to the CON group (P < 0.05; 49% vs 33%). In summary, synchronization increased the proportion of females that calved early in the calving season, and SEXED semen increased the proportion of the desired gender born early in the calving season.