Foundational reproduction programs for U.S. dairy herds.

Before the early 2000's, poor reproductive performance in U.S. dairy herds prevented commercial dairy farms from adopting assisted reproductive technologies. A reproduction revolution occurred in the U.S. dairy industry over the past 25 years during which the long-term decrease in reproductive performance dramatically reversed and began to increase. Although many factors are associated with increased reproductive performance (i.e., genetics, nutrition, management), the adoption of fertility programs by dairy farmers has driven much of this increase. Today, most U.S. dairy farms combine fertility programs with automated activity monitoring systems to inseminate cows, which has further increased AI service rates. A novel conceptual idea accompanying the dramatic increase in reproductive performance of lactating dairy cows is what has been coined "The High Fertility Cycle" which relates changes in BCS during the periparturient period with profound effects on pregnancy outcomes, pregnancy loss, and health events after submission of cows to fertility programs for first TAI. Taken together, these two factors have led to the historically high reproductive performance in U.S. dairy herds today. As a result, commercial dairy farms increased use of sexed dairy semen and beef semen and embryo transfer programs into their breeding programs. Rapidly shifting U.S. market prices for replacement dairy heifers and beef cattle will continue to affect how farmers allocate semen types within their herds moving forward. A major problem limiting the adoption of embryo transfer programs by commercial dairy farms is the associated high rates of pregnancy loss after establishment of pregnancy using embryo transfer compared with artificial insemination. Future research is needed to identify the underlying mechanisms of and strategies to mitigate pregnancy loss after embryo transfer before embryo transfer programs are widely adopted.