Follicular and luteal development in pregnant mares.

The research article investigates the interplay between various structures in the mare’s reproductive system throughout pregnancy. It establishes that the primary corpus luteum (CL), an endocrine structure in the ovaries, continues to function until at least day 160 of gestation, contributing to progesterone production. The study also touches upon the roles of the placenta, uterus, and secondary corpus luteum and introduces the effect of PMSG hormone on the mare’s ovarian functions.

Understanding the Research

• The heart of the research revolves around the behavior of certain aspects of the mare’s reproductive system during pregnancy. Specifically, the researchers focused on the ovaries, the corpus luteum (both primary and secondary), and the progesterone hormone.
• In the ovaries of mares, the primary corpus luteum (CL) is observed to remain functional until at least 160 days into the gestation period. The corpus luteum is a temporary endocrine structure involved in reproductive cycles and pregnancy and is primarily responsible for the production of the hormone progesterone.
• The research also notes that not only the primary and secondary corpus luteum but also the placenta or uterus contribute to the total pool of progesterone within mares during pregnancy.

PMSG’s Impact on Ovarian Function

• The paper reveals some interesting insights about the impact of PMSG (Pregnant Mare’s Serum Gonadotropin) on the mare’s reproductive system. The researchers noted that, while the hormone doesn’t stimulate the development of ovarian follicles, it does extend the lifespan and stimulate the secretory activities of the primary CL.
• Furthermore, PMSG is found to induce ovulation and/or luteinization of secondary follicles in pregnant mares. Ovulation refers to the release of an egg from the ovary, while luteinization pertains to the transformation process an ovarian follicle undergoes after ovulation to become a corpus luteum.
• Based on these observations, researchers point out the similarities and differences in ovarian function between pregnant and hysterectomized mares. A hysterectomized mare is one in which the uterus has been surgically removed (hysterectomy).