Author(s): Ginther OJ, Utt MD, Beg MA
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Abstract The temporal relationships between follicle deviation and systemic hormone concentrations were studied in mares. Blood samples were obtained at 01:00, 07:00, 13:00, and 19:00 h from nine mares throughout an interovulatory interval. Diurnal variation in progesterone occurred on Days 4-12 and in LH on Days 4 and 5; the lowest concentration for both hormones was at 13:00 h. Ultrasonically observed deviation in the ovulatory follicular wave began on Day 15.7+/-0.5 (ovulation=Day 0). An increase (P<0.002) in LH began on Day 14 before the beginning of deviation, and an increase (P<0.05) in estradiol began at the beginning of deviation. Testosterone concentrations began to increase (P<0.05) 2 days after the beginning of deviation and reached maximum 1 day before the next ovulation. The beginning of deviation was encompassed by a decline (P<0.003) in cortisol concentrations, and the concentrations remained low during the preovulatory period.
This article was published in Anim Reprod Sci
and referenced in Journal of Steroids & Hormonal Science