A review of patterns of change in luteal function.

The article presents a scientific review of the changes that happen in luteal function during different stages and conditions, focusing on livestock animals like pigs, cows, sheep, and horses.

Puberty and First Corpus Luteum

• In the case of gilts (young pigs) and fillies (young female horses), the first corpus luteum (an essential part of the ovulation cycle) appears to have a normal lifespan. It is generally associated with their first heat cycle (estrus) but can form even if estrus doesn’t occur.
• In contrast, ewes (female sheep) and cows have an initial period where progesterone, an ovarian hormone, rises and falls transiently before their first ‘normal’ corpus luteum. Interestingly, the appearance of a normal functioning corpus luteum in ewes doesn’t coincide with estrus, while in cows it may or may not coincide.
• However, more data is required to establish the variance in the lifespan of the first corpus luteum across these species.

Persistent Corpus Luteum

• The research also discussed the conditions in which the corpus luteum can persist longer without the presence of any abnormalities in the uterus. Evidence shows that this is most likely to occur in mares (adult female horses), may occur in ewes under continuous light conditions, is uncertain in cows, and is unreported in pigs.

Corpus Luteum after Anovulatory Season

• In sheep, it’s observed that after the period without ovulation (anovulatory season), there is a rise in progesterone over a 2-4 day interval approximately 25 days before estrus. During this phase, the progesterone pattern is similar to that of a normal heat cycle, even without the occurrence of estrus.
• For horses, the first corpus luteum after the anovulatory season usually coincides with estrus and has a typical lifespan. There is typically no prior progesterone rise, and it’s common to see estrus without formation of corpus luteum during the transition from anovulatory to ovulatory seasons.

Postpartum Corpus Luteum and Estrus

• The article further elaborates on the changes post-pregnancy. Notably, the corpus luteum of pregnancy regresses around the time of childbirth and doesn’t function thereafter in sows (adult female pigs) and cows.
• In mares, this regression happens around the 180th day of gestation, while in ewes, it happens post gestation day 140 and before day 2 postpartum.
• For sows and ewes, any estrus that happens within 1 to 3 days post childbirth is typically anovulatory. However, for mares, estrus within 5 to 12 days is associated with ovulation.

The analysis of these patterns provides a deeper understanding of reproductive physiology across different livestock animals and may be used for potential applications in animal husbandry and veterinary medicine.