Oestrogen pattern during early pregnancy in the mare.
Plasma total (conjugated + unconjugated) oestrogens were measured from Day 0 to 100 of pregnancy and compared with the levels found during the oestrous cycle. From Day 0 to 35 of gestation, the concentrations were similar to those during dioestrus. An increase in total oestrogens between Days 35 and 40 was followed by a plateau of 3 ng/ml between Days 40 and 60 which was slightly higher than preovulatory concentrations. This first increase in total oestrogen level was produced by the ovaries since values were suppressed after ovariectomy; stimulation may be due indirectly to PMSG causing follicular growth. After Day 60, a second increase was detected and considered to be of feto-placental origin as the levels at this time were not suppressed after ovariectomy. By Day 85, oestrogen concentrations exceeded thos detected in non-pregnant mares so that a direct measurement of total oestrogens in plasma by a simplified radioimmunoassay after Day 85 of gestation offers a reliable method of pregnancy diagnosis.
D000818:Animals; D002369:Castration; D004967:Estrogens / Q000097:blood*; D004971:Estrus; D005260:Female; D006736:Horses / Q000502:physiology*; D010060:Ovulation; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000097:blood; D013997:Time Factors
D004967:Estrogens; D011374:Progesterone