The Effects of Corpora Luteal Number on Serum Progesterone and Estradiol of Ewes During Luteal Phase of Estrous Cycle and Pregnancy

Abstract

Two experiments were conducted to study the effects of corpora luteal nuiuber on
maternal serum concentrations of progesterone and estradiol during luteal phase of estrous cycle and pregnancy. The experimental ewes were injected twice with l ml PGF2 to destroy previously existed corpora lutca. The number of corpora lutca was
counted by laparoscopy 5 days after the onset of estrous cycle. Blood samples were collected weekly during the estrous cycle and biweekly during pregnancy for hormone analyses using radioimimuioassay. Simple correlation was used to determine the relationship between the number of corpora lutea and progesterone or estradiol concentrations. Progesterone concentrations increased with the number of coipora lutca during the luteal phase of estrous cycle (P<0.05) (r = 0.34), the first half of pregnancy (P<0.01) (r = 0,48), the second half of pregnancy (P<0.0l) tr = 0.63), and during the whole gestation period (P<0.01) (r =0.63). However, seiuin estradiol concentrations decreased slightly with the ntunbcr of corpora lutea
(r = -0.09) during the luteal phase of the estrous cycle, then slightly increased during the first half of pregnancy (r = 0.02), the second half of pregnancy r I 0.33), and during the whole pregnancy (r = 0.30). The results suggested that the number of corpora lutea correlated more with the concentrations of progesterone than with those of cstradiol during the luteal phase of estrous cyclc, the first and the second half of pregnancy or during the whole period of pregnancy. It was concluded that endogenous secretion of progesterone and estradiol as inanunogenic honnoncs could bc increased by increasing the number of ovulating follicle during the estrous cycle.