Advances in reproductive management: pregnancy diagnosis in ruminants

During the last 10 years the U.S. dairy industry has experienced a reversal of the decades-long trend in declining fertility traits. In fact, there is evidence that, nationally, this is contributing to improvements in pregnancy rates. And while these measures are still close to their historical lows, there is reason for optimism that this reversal will continue into the future. The reasons for improved pregnancy rates are related to use of biotechnologies and improved management practices for high producing dairy cows as well as greater emphasis on genetic selection for fertility-related traits. Combined, these factors have resulted in a reduction in the average days to first service in our national dairy herd of approximately 10 days over the past decade and a reduction in calving interval of approximately 15 days. However, current challenges include accurate identification of cows that fail to conceive following insemination and their timely reinsemination. The primary metric for success of pregnancy diagnosis is the inter-service interval, or the number of days between insemination and the subsequent insemination in a cow that fails to conceive or that loses an established pregnancy. This trait is directly affected by the choice of pregnancy diagnosis method. Pregnancy diagnosis methods include estrous detection (visual or assisted), transrectal palpation of uterine contents, transrectal ultrasound visualization of uterine contents and assay for hormones in blood, milk or other body fluids. Each of these methods has advantages and disadvantages. Presently, ultrasound and blood hormone assay at 28 days after insemination offer the earliest specific diagnostics for determining pregnancy status. However, other methods are on the horizon that may provide opportunities to further reduce the interval between insemination and accurate diagnosis of pregnancy status of dairy cattle. One of these targets identification of failed inseminations 18 to 20 days after insemination. This approach, if successful, would allow identification of a portion of open cows prior to their expected return to estrus. The ultimate goal is to identify cows that fail to conceive to an insemination in time to reinseminate them at a normal cycle interval (21 to 23 days) while achieving high conception rates. Reproductive management programs that utilize early pregnancy diagnosis will reduce the interservice interval and improve pregnancy rate, which is a key metric in determining profitability on dairy