Progesterone in Bovine Reproduction: A Review

Abstract

This review, related generally to bovine reproduction, covers methods, metabolism and quantitative estimates of progesterone. Progesterone and 20/3-hy-droxy- [DELTA]4-pregnene-3-one appear to be the principal progestins in the corpus luteum (CL) of cycling and pregnant cows. Progestins have also been reported in bovine ovaries, adrenals, and blood. The CL appears to be the most important source of progesterone throughout bovine pregnancy. The CL from a previous cycle contains measurable progesterone for 2 or 3 days after estrus. Progestin in the CL and ovarian vein blood declines rapidly during proestrus from maximum levels observed 14-16 days post-estrus. In the pregnant cow, CL progestin levels decline about 40% from mid-cycle levels by 42-56 days of pregnancy, further decline slowly until 200 days, then rise again to the 28-day level; after 250 days, a decline to parturition begins. Similar changes are seen in blood levels of the hormones during pregnancy. Progesterone appears important in pregnancy maintenance, expression of estrus, normal cyclic function, and in hypophyseal-gonad interrelationships.