Pattern of plasma progesterone, oestradiol-17 beta, luteinizing hormone and androgen in non-pregnant buffalo (Bubalus bubalis).

Domestic buffaloes were used to characterize the pattern of progesterone, oestradiol-17 beta, LH and androgen in the systemic circulation following infertile insemination. Concentrations of hormones were measured by RIA in blood samples collected daily or at alternate days following insemination. The concentration of progesterone was lowest on the day of insemination, and increased significantly to a peak level of 4.00 +/- 0.60 ng/ml by day 13 post insemination. After day 17, it declined significantly (P less than 0.01) to reach low levels by day 21. The concentration of oestradiol 17-beta was high at the time of insemination and declined significantly (P less than 0.01) by day 2 after insemination. It was maintained around the basal level till day 18 with minor peaks in between this period. It again rose significantly (P less than 0.01) at subsequent oestrus. The mean level of LH was highest at the time of insemination, and declined significantly (P less than 0.01) by day 1 post insemination. It did not vary appreciably till the animal returned to oestrus. The oestrous value of LH and progesterone were negatively correlated (r = -0.77). The androgen level was observed to be high at insemination in 3 out of 5 animals, but the overall pattern of this steroid was inconsistent during the period studied. A high concentration of androgen was recorded in all the animals from day 2--5 before the onset of oestrus.