Hair Allopregnanolone in Mares and Foals as a Retrospective Biomarker of Predicting Feto-Maternal Well-Being

Assay of steroid hormones in hair has become an attractive alternative for studies focusing on the perinatal period in equine medicine. The aim of the present study was to evaluate mares’ and foals’ hair ALLO concentrations and their ratio in relation to clinical conditions and selected clinical parameters. The 37 mare–foal pairs were categorized into healthy (group H; n = 15) and sick (group S; n = 22) groups. ALLO from hair was measured using a commercial ELISA kit. Foal ALLO and foal/mare ALLO ratio were lower in group S compared to group H (p < 0.001). Moderate positive correlations were found between both the foal ALLO and foal/mare ALLO ratio and the mare’s gestation length (p = 0.003; r = 0.476 and p = 0.002; r = 0.487), between the foal ALLO and foal’s weight (p = 0.042; r = 0.336), and between the foal/mare ALLO ratio and foal’s Apgar score (p = 0.047; r = 0.410). Based on a logistic regression model, a strong relationship (R2 = 0.75) emerged between ALLO concentrations and foals’ clinical outcome, with concentrations of the hormone predicting foals’ clinical outcome with high accuracy (86.8%). Decreased foal ALLO and foal/mare ALLO ratio in sick foals appear to be potential biomarkers of prenatal disease toward the end of pregnancy.