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The 21-d pregnancy rate is determined by an interaction between the AI service rate and pregnancies per AI (P/AI) and is a key performance indicator for the reproductive efficiency of dairy farms. Over the past 2 decades, the reproductive performance of lactating dairy cows increased. A greater understanding of endocrinology and the physiology of lactating dairy cows generated fertility programs (the Presynch-Ovsynch and Double Ovsynch protocols for TAI) that increase the service rate and P/AI compared with detection of estrus. Previously, synchronization of ovulation in heifers was associated with poor reproductive performance compared with detection of estrus. Several modifications determined through randomized-controlled studies gave rise to the 5-d CIDR-Synch protocol that has similar and more P/AI when heifers are inseminated with conventional and sexed semen, respectively, compared with detection of estrus. A hierarchy of reproductive needs exists for dairy farms that require fulfillment before a new need can emerge. Dairy farms must have a high 21-d pregnancy rate and good heifer management before adopting other advanced reproductive technologies such as genomic selection, sexed and beef semen, and in vitro-produced embryos. Adopting these advanced reproductive technologies benefits dairy farms, however, challenges still exist that need further investigation through randomized-controlled experiments to maximize the benefits
M.R. Lauber (Tue,) studied this question.
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