Effects of maternally administered depot ACTH(1-24) on fetal maturation and the timing of parturition in the mare.

This research aims to explore the effects of administering adrenocorticotrophic hormone (ACTH) to pregnant mares to see whether it can promote more rapid fetal development and induce earlier birthing. The study found that higher doses of ACTH could hasten fetal maturation and delivery, particularly among mares that mated late in the breeding season, though further research is needed to confirm these findings and outline clinical recommendations.

Purpose and Methodology of the Study

• The objective of this study was twofold. The researchers wanted to determine if fetal maturity in mares could be expedited through the maternal administration of adrenocorticotrophic hormone (ACTH). They also sought to evaluate whether such maturation could occur without posing major risks to the mare or her unborn foal.
• Twenty-two mares were selected for the study, with each given either a low dose (1 mg, referred to as LD) or high doses (4 or 5 mg, referred to as HD) of a synthetic variant of ACTH at specific stages of gestation (days 300, 301, and 302).
• The mares were segregated retrospectively into different groups based on their mating period: those that mated before July 1 and those mated after. For mares given HD ACTH, further segregation was made, forming two subsets named HDE and HDL, respectively.

Findings

• Post ACTH administration, all mares exhibited a notable increase in plasma progestagen and cortisol concentrations. This rise was longer and higher among HD mares.
• ACTH administration spurred mammary growth and fluctuations in milk electrolytes in HD mares.
• The study found that mares from the HDL group had significantly shorter gestation periods in comparison to those in the LD, HDE, and untreated groups.
• Almost all the foals were mature, except for two stillbirths in the HDL group.
• Among the mature foals, the HDL group had higher mean cell volume (MCV) values but lower mean body weights, suggesting their birth transpired ahead of the full gestation period.

Conclusion

• The findings imply that maternal ACTH administration can potentially accelerate fetal development and delivery in pony mares, specifically those given high doses and mated towards the end of the breeding season.
• However, before these findings can be applied clinically, further investigation is necessary to determine the best gestational age and dosage for ACTH therapy.