Hormonal changes around bovine luteolysis

Plasma concentrations of estradiol-17beta, progesterone, LH and 13, 14-dihydro-15-keto-PGF2alpha were determined by radioimmunoassay on 2-hourly samples obtained around luteolysis and estrus in three dairy cows. The decline in progesterone occurred before the preestrous rise in estrogen and no pre-estrous peak of progesterone could be detected. The major activity of prostaglandin coincided, with declining progesterone levels and the active stage of estrogen secretion.