Effect of altrenogest-treatment of mares in late gestation on adrenocortical function, blood count and plasma electrolytes in their foals.
Authors: Neuhauser S, Palm F, Ambuehl F, Möstl E, Schwendenwein I, Aurich C
Journal: Equine veterinary journal
Summary
# Editorial Summary Mares with at-risk pregnancies frequently receive altrenogest to prevent abortion, yet limited evidence exists regarding its effects on fetal development during the critical final weeks before birth. Neuhauser and colleagues administered altrenogest (0.088 mg/kg daily) to six pregnant mares from day 280 of gestation through foaling, comparing neonatal outcomes with seven untreated control mares across measures of immune function, cortisol responsiveness, and electrolyte balance. Foals exposed to altrenogest demonstrated a significantly lower neutrophil/lymphocyte ratio on day one of life, elevated basal cortisol immediately post-partum, and notably reduced plasma potassium and ionised calcium concentrations—though ACTH stimulation tests showed no clinically meaningful differences in adrenocortical responsiveness between groups. The immunological shift and electrolyte findings suggest possible dysmaturity or immunomodulatory effects rather than severe endocrine dysfunction, implying that whilst altrenogest successfully maintains pregnancies to term, practitioners should monitor neonatal electrolyte status closely and remain alert to any indicators of compromised immune competence during the critical early post-partum period.
Read the full abstract on PubMed
Practical Takeaways
- •Altrenogest treatment in late pregnancy for abortion prevention does not significantly impair adrenocortical function in newborn foals, supporting its continued use when clinically indicated
- •Monitor foals born to altrenogest-treated mares for altered immune markers (reduced neutrophil/lymphocyte ratio) and electrolyte abnormalities (lower potassium and ionised calcium), particularly in the first 3 hours post-birth
- •The reduced neutrophil/lymphocyte ratio may indicate dysmaturity; assess foal maturity indices carefully when altrenogest has been used during final gestation
Key Findings
- •Foals from altrenogest-treated mares had significantly lower neutrophil/lymphocyte ratio on day 1 post-birth compared to controls (P<0.05)
- •Basal plasma cortisol concentrations were higher in foals of altrenogest-treated mares immediately after birth (P<0.05)
- •Plasma potassium concentration was significantly lower in foals from treated mares immediately after birth (P<0.05)
- •Plasma ionised calcium concentration was significantly lower in treated group foals at 3 hours post-birth (P=0.01)