Abstract
Reproductive efficiency is a major factor contributing to efficiency, profitability and sustainability of dairy farms. Estimates of economic loss due to reproductive inefficiencies range from $1 to 5 billion per year. Given the decreasing trend of conception rates during the past 30 years, it can be anticipated that fertility of lactating dairy cows will continue to be a paramount challenge to profitable dairy herd management. The exact physiological reasons for poor fertility of lactating dairy cows are unknown. This presentation focuses on correcting limitations of Ovsynch in addition to understanding the fertility potential of an ovulatory follicle by controlling its age, size, and function. Ovsynch can improve pregnancy rates when estrus detection rates are poor and inaccurate, leading to improper timing of artificial insemination in relation to ovulation. However, inadequate synchronization rate of Ovsynch limits its effectiveness. The focus of our research program is to determine if fertility of lactating dairy cows can be increased by modifying Ovsynch to control emergence of the ovulatory follicular wave and initiate ovulation at the prime stage of development of the synchronized ovulatory follicle. Our ultimate goal is to devise an exogenous hormonal control strategy using gonadotropin-releasing hormone (GnRH) and prostaglandin F2α (PGF2α) that reduces age, yet optimizes size and function, of the ovulatory follicle of Ovsynch. Based upon strong published data, it is our contention that control of ovulation to the first GnRH of Ovsynch, appropriate timing of luteolysis and the final GnRH-induced luteinizing hormone (LH) surge are essential for the synchronous emergence, development, and synchronized ovulation of the ovulatory follicle.
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