Hair steroid hormones concentrations in jennies and their donkey foals from parturition to 6 months postpartum.

Overview

• This study examined the levels of various steroid hormones in the hair of mother donkeys (jennies) and their foals from birth to six months postpartum to better understand hormonal changes during this critical period.
• The research highlighted differences in hormone concentrations between jennies and foals, indicating distinctive physiological adaptations of the hypothalamic-pituitary-adrenal (HPA) axis after birth in both groups.

Background and Purpose

• The postpartum period is a critical phase involving significant physiological changes regulated by hormones, particularly through the HPA axis.
• This period has been well-studied in horses but less so in donkeys, although such knowledge is important for conservation and management of endangered donkey breeds.
• The study aimed to measure concentrations of six hormones (cortisol [C], dehydroepiandrosterone sulfate [DHEA(S)], 17-β-estradiol [E2], progesterone [P4], testosterone [T], and allopregnanolone [AlloP]) in the hair of Martina Franca jennies and their foals from birth to six months postpartum.

Methodology

• Subjects: 10 Martina Franca jennies and their 10 donkey foals.
• Sampling: Hair samples were collected at birth (T0) and then monthly up to six months postpartum (T1-T6).
• Hormones analyzed included:
• Cortisol (C) – a primary stress hormone regulated by the HPA axis.
• DHEA(S) – a hormone involved in counteracting cortisol’s effects and modulating HPA activity.
• 17-β-estradiol (E2) – a form of estrogen involved in reproductive physiology.
• Progesterone (P4) – a hormone important in pregnancy and postpartum physiology.
• Testosterone (T) – an androgen hormone, differing by sex and developmental stage.
• Allopregnanolone (AlloP) – a neurosteroid influencing stress and neurological functions.
• Hair concentrations of these hormones represent integrated secretion over weeks to months, providing insight into longer-term physiological changes.

Key Findings

• Differences at Birth:
• Donkey foals exhibited higher cortisol and allopregnanolone hair concentrations at birth compared to their mothers.
• Foals also showed a higher cortisol to DHEA(S) ratio, suggesting a stronger activation of stress-related pathways at birth.
• Hormonal Profiles Over Time:
• Distinct hormone profiles were observed when comparing foals and jennies for almost all hormones except for DHEA(S), testosterone, and allopregnanolone.
• Both jennies and foals showed significant decreases in:
• Allopregnanolone between birth (T0) and months 1 to 6 postpartum (T1-T6).
• DHEA(S) and testosterone between birth (T0) and months 2 to 6 postpartum (T2-T6).
• Sex Differences in Foals:
• Male foals demonstrated higher hair cortisol concentrations and cortisol to DHEA(S) ratios at 90 days old compared to females.
• Note: This finding is based on a small sample size and should be interpreted cautiously.

Interpretations and Implications

• The elevated cortisol and allopregnanolone levels in foals at birth indicate a heightened activation of the HPA axis possibly related to the stress of birth and early adaptation to the environment.
• The lowering of certain hormones over the postpartum period suggests maturation or stabilization of endocrine functions in both dams and offspring.
• The differences between jennies and foals in hormone profiles reflect distinct physiological states and demands in mothers versus neonates during the first six months postpartum.
• Sex-related differences in cortisol and its ratio to DHEA(S) hint at possible variations in stress responses between male and female foals, warranting further research with larger groups.
• Understanding these hormonal changes in donkeys can inform better management and conservation strategies, especially for endangered breeds where physiological insights are limited.

Limitations

• Small sample size (10 jennies and 10 foals) limits the generalizability of the findings.
• Some findings, especially sex differences, require cautious interpretation due to limited subject numbers.
• Study focused solely on Martina Franca donkeys; other breeds might exhibit different hormone profiles.

Summary

• The study provides novel insights into postpartum hormonal adaptations in donkeys by analyzing hair steroid hormone concentrations over six months after birth.
• It reveals distinct and dynamic hormonal changes in both jennies and foals, with certain hormones decreasing over time, highlighting different physiological needs and stress adaptations during this critical period.
• These results address a gap in knowledge about donkey reproductive and developmental endocrinology and have potential applications in animal welfare and species conservation.