Endocrine patterns of the mare at term.

This is a research article that explores the changes in the levels of progesterone, total progestins, oestrogen, and corticosteroids in a mare approaching, during, and after giving birth.

Research Objectives and Findings

• The researchers looked into the variations of progesterone and total progestins, oestrogen, and 11beta-hydroxycorticosteroids levels in pregnant mares. This investigation spanned from late pregnancy through to parturition and into the post-partum period.
• The study revealed that both progesterone and total progestins levels increased during the final stages of pregnancy, only to experience a sharp decrease just before birth. Nonetheless, significant amounts of plasma progesterone were still present when the mare gave birth.
• Oestrogen levels were found to slowly decrease throughout this period, although the decline was not significant. These levels remained low from parturition until the post-partum oestrus, which occurred 10 to 12 days after birth.
• The levels of 11beta-hydroxycorticosteroids did not change significantly from 45 days before to 15 days after the birth.

Ovariectomized Mares

• The research also investigated an ovariectomized pregnant mare in the last month of gestation. The hormone levels in this case matched that of the intact mares.

Post-Partum Period

• Upon reaching the post-partum ovulation, a typical cyclic pattern of progesterone and total progestins was observed.
• While there were no significant changes in oestrogen levels, corticosteroid levels showed a notable increase between the 15th and 22nd days post-partum.

Comparison with Foals

• The study also compared the hormone levels between the mare and the newborn foal within the first 24 hours after birth. In all cases, the foal showed higher levels of progestin, oestrogen, and corticosteroids than in the maternal plasma.