Gonadal steroid hormone level in blood plasma and milk of primiparous and multiparous nonpregnant and pregnant buffaloes

Abstract Changes in the concentration of progesterone and estradiol-17β were measured by radioimmunoassay in 11 primiparous and 17 multiparous buffaloes at estrus and daily post insemination and in 6 nonbred buffaloes at 6 hour intervals from 4 days before expected estrus to one day after estrus. Plasma progesterone concentration at estrus was 0.1 ng/ml which rose to a peak level of 3.47 ng/ml on day 17. It fluctuated around this level in those animals which conceived, but followed a declining trend in those which failed to do so and attained lowest values on the day of next estrus. Temporal changes of the hormone revealed that the occurrence of major decline varjed between 16 and 62 h before estrus. The average concentration in milk was about three to four times higher than in plasma. The concentration of estradiol-17β about 23.50 pg/ml at estrus and fluctuated around 10 pg/ml in animals that returned to estrus with a peak around estrus. Temporal changes of hormone revealed that peak level occurred 8–17 h before estrus. The concentration of estradiol in pregnant animals fluctuated around 10 pg/ml. The concentration in milk was about 2–3 times higher than in plasma. There was no significant (P > 0.05) difference in the concentrations of progesterone and estradiol-17β between primiparous and multiparous animals.