Location: Range and Livestock Research2010 Annual Report
1a. Objectives (from AD-416)
To improve our understanding of the mechanism(s) by which pre-ovulatory estradiol concentration and a prolonged pro-estrus affect embryo development and pregnancy establishment in beef cattle.
1b. Approach (from AD-416)
Mechanisms controlling fertility of single matings in beef cattle are poorly understood, especially cows that exhibit estrus. The scientists involved with this agreement from both institutions will share data and research efforts to identify mechanisms controlling fertility and their effects on early embryo development, pregnancy establishment and maintenance. This research will include evaluation of serum estradiol and luteinizing hormone collected from cows around the time of ovulation and the role of these hormones on oocyte maturation, fertilization, early embryo development, and the ability of differentially developed oocytes to establish viable pregnancies. The USDA-ARS, Fort Keogh, Miles City, MT, has a majority of the cattle used for these studies, and the research involved with these studies will occur at Fort Keogh.
3. Progress Report
Collection and transfer of embryos from cows that ovulated either large or small follicles into cows that ovulated different sized follicles was completed and suggested a disconnect in the role that ovulatory follicle size has on fertilization, early embryonic health, pregnancy establishment and pregnancy maintenance. More specifically, the role of serum estradiol concentration at the time of ovulation in the aforementioned study was evaluated. Concentration of estradiol in the blood at the time of ovulation was highly correlated to ovulatory follicle size and had direct, but independent effects on fertilization success, serum progesterone concentration in the subsequent luteal phase, and pregnancy establishment. A manuscript detailing these results is in preparation. We have also initiated a study further investigating the roles of age and hormonal growth environment of the ovulatory follicle, and ovulatory follicle size at ovulation on serum estradiol concentration at breeding and pregnancy success. ADODR monitoring is done via phone calls and e-mails.