Pregnancy per AI in Holstein heifers inseminated with sex-selected or conventional semen after estrus detection or timed-AI.

This study compared pregnancy per AI (P/AI) of heifers inseminated with sex-selected or conventional semen after estrus detection (ED) or timed-AI (TAI). Heifers in the ED group received 2 treatments with prostaglandin F2α 14 d apart and those in the TAI group received a modified 5-day Co-synch protocol plus an intravaginal progesterone releasing insert device (PRID) and were inseminated 72 h after PRID removal. Overall P/AI were 69.2% (74/107) and 64.1% (75/117) for conventional and sex-selected semen (P > 0.05). Although P/AI in ED heifers following the use of conventional semen were numerically higher (75.0% versus 63.6%), P/AI with sex-selected semen were almost identical (65.0% versus 63.2%) for ED and TAI heifers. Pregnancy losses from first pregnancy diagnosis to term did not differ between ED and TAI heifers (6.0% versus 11.3%). In summary, heifers subjected to TAI with sex-selected semen following the application of a modified 5-day Co-synch plus PRID protocol had acceptable P/AI.