Concentrations of progesterone and 17β-estradiol in blood and milk and those of natural inhibitors in milk of goats in various

The aim of the study was to investigate how the physiological condition of goats affects the contents of progesterone and 17β-estradiol in the blood and milk and the presence of natural inhibitors in milk. The experimental material consisted of the milk and blood from 13 twoand three-year old goats, in which heat and ovulation were synchronized. Blood and milk samples were collected in the consecutive days, counting from the moment of ovulation: -47, -19 (the day of sponge administration), -2, 0, 2, 6, 18, 21, 40, 66 and 104. The presence of natural inhibitors in milk was determined using BRT. The concentrations of progesterone and 17β-estradiol in the blood and milk were radioimmunoassayed using tagged hormones [ I]. The highest concentration of estradiol in blood (76.26 pmol/l) was found 2 days before ovulation. Progesterone content reached a very high level starting from the 6 day of pregnancy, assuming the value of ca 62.5 nmol/l on day 66 and 104 of pregnancy. The levels of both progesterone and estradiol in milk were strongly correlated with the content of a given hormone in blood (r >0.9; p=0.0001). BRT showed the presence of inhibitors in the milk of all the investigated goats on the 6 day after ovulation, which may not be explained either by the action of progesterone, or estradiol per se.