Level of gonadotropic hormones in the blood plasma of cows during the sexual cycle

: Studied was the level dynamics of the pituitary gonadotropic hormones (FSH and LH) in the blood plasma of five cows of the Bulgarian Brown breed. During the estrus cycle an average of 12 samples of 100-150 cu. cm citrate blood were taken from each cow. The determination of FSH was performed after Brown's method, and that of LH - after Parlow's method. It was concluded that both FSH and LH consistently enter the blood during the estrus cycle. Their concentration in the peripheral blood changes in accordance with the phase of the estrus cycle. During this period two peaks in the release of gonadotropic hormones in the peripheral blood are established: one at the time of estrus itself, and another after the first half of the heat cycle.