84 Conception Rates in Beef Cattle Inseminated with Either Sexedultra™ or Conventional Semen after Ovulation Is Synchronized for Fixed Time Artificial Insemination Using a 14-Day Cidr-PG Modified Protocol

Abstract The objective of this study was to determine if conception rates to fixed-time artificial insemination (FTAI) differ between SexedULTRA™ sex-sorted (SU) and conventional (CON) semen when ovulation is synchronized using a modified 14-d controlled internal drug release (CIDR) - PGF2α (PG) protocol. This protocol was modified to optimize the time FTAI occurs in relation to ovulation. Treatments included CON or SU with three sires represented on each treatment. Heifers (n=218) from one location were randomly assigned treatment. Females were synchronized using a modified 14-d protocol CIDR-PG protocol. Heifers received a CIDR insert (1.38 g progesterone) from d 0 to 14, followed by dinoprost tromethamine (PG; 25 mg i.m., Lutalyse)16 d later (d 30). All females were administered gonadorelin (GnRH; 100 ug i.m., Factrel) 54 h after PG and FTAI occurred 18 h after GnRH (72 h after PG administration). Estrotect™ estrous detection aids were applied at PG administration and patch coloration was recorded at insemination to indicate estrous expression. Animals were assumed estrual if greater than 50% of the patch coating was removed. Heifers were exposed to natural service sires 7–10 days after FTAI for the remainder of the breeding season. Conception rates to FTAI were analyzed using PROC GLIMMIX in SAS 9.4 and the effect of technician and final pregnancy rates by treatment were analyzed using the ANOVA procedure. For all data analyses significance was determined at p