A review of patterns of change in luteal function

Puberty: For the gilt and filly, the first corpus luteum (CL) appears to have a normal lifespan. For both species, first CL usually is associated with estrus but can form in the absence of estrus. For the ewe and cow, a transient (1 to 4 d, ewe; 3 to 10 d, cow) rise and fall of ovarian derived progesterone (P4) is detected in peripheral blood (80% of ewes; 50% of heifers) prior to first "normal" CL. The first CL of apparent normal lifespan is not accompanied by estrus in the ewe. The first CL in the cow may or may not be accompanied by estrus; first estrus in the cow can be anovulatory. Data are required to describe definitively variation in lifespan of first CL in these species. Persistent CL: Data that the CL can be prolonged in the absence of uterine abnormality are strongest in the mare, suggestive for the ewe under conditions of "more constant light," equivocal in the cow, and not reported in the pig. First CL after the anovulatory season: As reported for the pubertal ewe, the anestrous ewe can have a progesterone rise over a 2- to 4-d interval at about 25 d before estrus. The ewe has a P4 pattern similar to that of a normal estrous cycle in the absence of estrus immediately prior to the first estrus and CL. CL lifespan was reported for the first estrous cycle to be both normal and on the order of 4 to 10 d in up to 50% of the ewes, following introduction of rams. For the mare, first CL usually is associated with estrus and has a normal lifespan. Data suggest no P4 rise prior to first CL. The occurrence of estrus without formation of a CL is usual during the anovulatory season and during the transition from anovulatory to ovulatory seasons. Postpartum: The CL of pregnancy regressed at parturition and was not functional postpartum in the sow and cow, regressed at about d 180 of gestation in the mare (both primary CL and secondary CL), and regressed after d 140 of gestation and before d 2 postpartum in the ewe. Postpartum estrus occurring within d 1 to 3 postpartum was anovulatory for both the sow and ewe; postpartum estrus within d 5 to 12 was ovulatory for the mare.(ABSTRACT TRUNCATED AT 400 WORDS)