2008 Annual Report 1a.Objectives (from AD-416) To improve our understanding of the mechanism(s) by which ovulatory follicle size affects pregnancy establishment and embryonic mortality. 1b.Approach (from AD-416) ARS – A student from Conapec will visit the Fort Keogh Livestock and Range Research Laboratory (LARRL) and evaluate the effects of serum estradiol and ovulatory follicle size on embryo quality & morphology, and pregnancy establishment & maintenance in beef cows. Conapec – members will evaluate effects of exogenous estradiol cypionate, equine chorionic gonadotropin, and temporary calf removal on ovulatory follicle size, and establishment / maintenance of pregnancy in large beef herds in Brazil. Information will be mutually shared between involved parties. 3.Progress Report Individual embryos have been flushed from embryo donor cows on day 7 following artificial insemination. Embryos were evaluated for morphological development and embryo quality, and all viable embryos that were recovered were transferred to embryo recipient cows within 5 hours of recovery. Approximately two-thirds of the required 360 embryos have been collected, evaluated and transferred. We have evaluated pregnancy in approximately one-half of the embryo recipient cows to date, but still need to evaluate estradiol concentrations in these cows at the time of artificial insemination. ADODR monitoring activities include technical oversight at Fort Keogh, conference calls, e-mails, and phone calls.