Progestagen, oestrone sulphate and cortisol concentrations in pregnant mares during medical and surgical disease.

This research investigates the concentrations of cortisol, oestrone sulphate, and progestagens in 22 stressed pregnant horses to determine their usefulness as indicators of the viability of the fetus. The horses were classified according to their clinical diagnoses, and it was found that plasma cortisol levels were generally higher in stressed mares, with this increasing further during post-admission complications.

Methodology

• Forty-four horse pregnancies were investigated with horses suffering from conditions such as surgical colic, medical colic, and uterine torsion.
• The horses were bled every 12 hours from the time of their admission.
• The plasma from these samples was stored at negative 70 degrees Celsius until it was ready to be examined.
• Normal horses were also bled twice a week starting from Day 270 of gestation until they gave birth, to establish baseline endocrine data.
• The concentrations of cortisol and progestagens were measured by radioimmunoassay, while oestrone sulphate levels were measured using enzyme immunoassay.

Results

• Of the 16 horses in the first two groups that survived to discharge, 12 horses gave birth normally, while 4 aborted.
• After surgical treatment for uterine torsion, two horses aborted and two successfully carried their foals to term.
• Plasma cortisol levels were over 30 ng/ml in 19 out of the 22 stressed horses at presentation, which is higher than the cortisol levels in normal horses.
• The average cortisol concentration of horses that aborted due to colic was found to be higher than in horses that did not abort, but the difference was not statistically significant.
• In normal circumstances, the progestagen concentrations in the horses ranged from 2 to 25 ng/ml.

Conclusion

• This study has found that cortisol levels in the plasma are generally higher in horses under stress, and these levels further increase after further complications after being admitted to the hospital.
• However, while the cortisol concentrations of horses that suffered colic and then aborted were higher than those of horses that did not abort, the difference was not statistically significant.