Effects of administration of exogenous estradiol benzoate on follicular, luteal, and uterine hemodynamics in beef cows.

Abstract Objectives of these two experiments were to determine if exogenous estradiol benzoate (EB) affects follicular, luteal, and uterine hemodynamics. In both experiments, 77 estrous-synchronized beef cows were assigned to one of two treatments: 1) Control (CON) or, 2) an injection of 1 mg EB the day before expected estrus (Day 0; Experiment 1) or on the day of estrus (Day 1; Experiment 2). There was transfer of an embryo (Day 7) into cows that expressed estrus. In Experiment 1, estradiol concentrations in circulation at Day 0 were greater in EB-treated cows (P = 0.003); however, concentrations of progesterone were only greater (P = 0.03) at Day 21 in cows of the EB-treated compared to those in the CON group. The follicular and luteal blood perfusion was similar, however, treatment with EB resulted in a greater uterine blood perfusion. In Experiment 2, treatment with EB did not affect size or blood perfusion of the corpus luteum (CL) on Day 7, 14, and 21. Only on Day 21, however, did pregnant cows have a larger CL than non-pregnant cows (P = 0.02). Blood perfusion to the CL was greater (P