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Over the past 2 decades, a reproduction revolution has occurred in the dairy industry in which average 21-d pregnancy rates have more than doubled from around 14% to more than 30% in many herds. Much of this increase in reproductive performance has been driven by development and adoption of fertility programs. Despite the dramatic increase in 21-d pregnancy rates, substantial variation exists among herds using the exact same reproductive management, suggesting that factors other than fertility programs can affect fertility. Change in body weight or body condition score postpartum or during the periparturient period dramatically affects embryo quality, reproductive outcomes, and transition cow health. Although some cows lose body weight or body condition score after calving, some cows maintain, whereas some cows even gain body weight or body condition score during this time period. Surprisingly, milk production during early lactation is not affected based on body condition score change during the first 3 weeks postpartum; however, peak milk measured near 60 DIM was less in both primiparous and multiparous cows that either gained or maintained compared to cows that lost body condition during the 1st 30 DIM. The high fertility cycle coupled with the dramatic increases in reproductive performance due to the development and adoption of fertility programs is a new paradigm that we can now use to explain much of the variation in reproductive performance among herds. The high-fertility cycle: how timely pregnancies in 1 lactation may lead to less BCS loss, fewer health issues, greater fertility, and reduced early pregnancy losses in the next lactation., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2020

Twinning in Holstein dairy cows has increased over time concurrent with increased milk production. More than 95% of twins in Holsteins arise due to double ovulations resulting in dizygotic twins. It is now clear that low progesterone during growth of a preovulatory follicle increases the incidence of double ovulation. Increased hepatic metabolism of progesterone as a result of the increased feed intake associated with high milk production provides a physiological mechanism for decreased progesterone levels in high-producing dairy cows resulting in an increase in di zygotic twinning. Twinning will likely continue to increase with milk production over time, so strategies to effectively manage twinning in dairy cows need to be identified and implemented. Cows carrying unilateral twins had greater pregnancy loss compared to cows carrying bilateral twins, and bilateral twins had increased survival and body weight at birth, a longer gestation length, and less dystocia than unilateral twins. Selective embryo reduction by manual rupture of the amnion followed by progesterone treatment did not increase the risk of pregnancy loss for cows with unilateral twins but increased the risk of loss for cows with bilateral twins. Hormonal synchronization protocols that increase progesterone during development of the preovulatory follicle increase conception rate, decrease pregnancy loss, and decrease double ovulation rate thereby decreasing twinning in high-producing dairy cows. Twinning can be decreased in high-producing dairy cows using a two-pronged approach. First, the incidence of double ovulation and dizygotic twinning can be decreased in high-producing Holstein cows by manipulating ovarian function to increase progesterone during growth of the preovulatory follicle before timed AI. Second, cows identified with bilateral twins using transrectal ultrasonography early during gestation should be allowed to continue gestation with extra assistance provided at calving, whereas selective reduction can be attempted for cows diagnosed with unilateral twins., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2015

Early identification of non-pregnant dairy cows and heifers post-breeding can improve reproductive efficiency and pregnancy rate by decreasing the interval between artificial insemination (AI) services and increasing AI service rate. Thus, new technologies to identify non-pregnant dairy cows and heifers early after AI may play a key role in management strategies to improve reproductive efficiency and profitability on commercial dairy farms. Transrectal palpation is the oldest and most widely used method for early pregnancy diagnosis in dairy cattle7 • However, a newer technology may someday replace transrectal palpation as the method of choice for pregnancy diagnosis in the dairy industry. Before this transition can occur, two events must transpire. First, a technology must be developed that exceeds transrectal palpation in one or more of the characteristics of the ideal early pregnancy test. Second and no less important, this new technology must be practically integrated into a systematic, on-farm reproductive management strategy and empirically demonstrated to exceed the status quo of the industry (i.e., transrectal palpation) in reproductive performance. Results from a recent study indicate that positive pregnancy outcomes diagnosed by transrectal ultrasonography conducted 26 days after timed AI (TAI) may be inflated due to pregnancy loss, compared to pregnancy outcomes conducted 33 days after TAI. Furthermore, fertility to TAI after re-sychronization of ovulation was greater when initiated 33 days after TAI compared to 26 days. These results suggest the counterintuitive notion that delaying pregnancy diagnosis from 26 to 33 days post-TAI may improve reproductive efficiency when using a hormonal protocol for timed AI to program non-pregnant cows for rebreeding. This is due to the high rate of pregnancy loss occurring in cows diagnosed pregnant at 26 versus 33 days post-TAI., American Association of Bovine Practitioners Proceedings of the Annual Conference, 2006