Studies on fetal, neonatal and maternal cortisol metabolism in the mare.

This research study investigates the levels of cortisol, a stress hormone, in unborn foals and their mothers during different stages of pregnancy, as well as immediately before and after birth.

Objective of the Research

• The researchers aimed to understand the variability of cortisol levels in the bloodstreams of unborn foals and their mothers during various stages of pregnancy. Additionally, they evaluated the alteration in these levels before and after the process of parturition (birth).

Procedure and Methodology

• In this research, umbilical catheters were placed in ten animals to measure the concentration of cortisol in the fetal plasma from 227 to 310 gestational days.
• The researchers also estimated maternal cortisol values during this same period, which did not significantly change.
• Cortisol production rates were quantified at the 291st gestational day in two of the fetuses.
• For three fetuses nearing their birth (319 to 321 gestational days), cortisol values were recorded 1 to 10 days before birth.
• Moreover, the researchers analyzed cortisol concentrations after birth, in both healthy foals and those who suffered from postnatal convulsions.
• The study also included foals born prematurely, measuring their cortisol levels before and after birth.

Findings of the Research

• Cortisol levels in fetal plasma varied within the range of 13.9 +/- 1.5 ng/ml (at 227 to 244 days) to 18.1 +/- 2.2 ng/ml (at 290 to 310 days), while maternal cortisol levels remained relatively stable at 15.9 +/- 1.7 ng/ml.
• The cortisol production rate was found to be around 3.6 to 3.8 mg/kg/day, indicating a minimal placental transfer of cortisol.
• The unborn foals’ cortisol levels rose to about 30 to 50 ng/ml just before birth, ensuring comparability with cortisol levels in healthy, fully delivered foals.
• The cortisol concentrations dropped rapidly after birth except in foals that experienced post-birth convulsions, where very high values were detected.
• Prematurely born foals maintained low cortisol levels both before and after birth, similar to the levels found in one catheterized foal.

Significance of the Research

• This study provides crucial insights into understanding cortisol metabolism in horses during different stages of pregnancy, which may have implications in managing maternal and neonatal health.
• The findings could help veterinarians predict whether newborn foals are likely to experience post-natal complications based on their cortisol levels, thus enabling timely medical interventions.