Evaluation of later timepoints for fixed-time artificial insemination of beef heifers and cows when using sex-sorted semen.

Two experiments were designed to evaluate later timepoints for fixed-time artificial insemination (FTAI) of beef heifers and cows, with the hypothesis that use of a later timepoint would allow a greater proportion of animals to express estrus prior to FTAI and result in greater conception rates among estrous females inseminated with sex-sorted semen. In Experiment 1, estrus was synchronized for 1640 heifers using the 14 d CIDR-PG protocol: insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) on Day -33 and removal on Day -19, and administration of prostaglandin F (PG; 500 μg cloprostenol sodium) on Day -3.