Equine appeasing pheromones (EAP) slightly influences maternal serum serotonin response to a short separation from foal: a preliminary study

Appeasing pheromones are odorless volatile compounds secreted after delivery in all female mammals that induces a good emotional status of the offspring. Potential therapeutic applications of appeasing pheromones have been extensively studied in stressful events. Serotonin (5-HT) is suggested to be a modulator during stress. The aim of this study was to evaluate if an analogue synthetic of Equine appeasing pheromone (EAP) applied as nasal gel could modulate 5-HT responses of mares in the context of a short separation from their foals. Eight mares with their foals were randomly allocated to treatment (A) or control group (B). The day of separation EAP or placebo was applied to the mother in the form of an intranasal wipe by a handler. Blood sampling was performed 30 min prior to separation (T0 and treatment administration), at 30 after separation (T1) and 30 min after the return of the mother in the box (T2). 5-HT serum concentration was measured by ELISA. The effects of treatment (A vs B), time (T0 vs T1 vs T2) and time ∗treatment interaction were analyzed by a two-way ANOVA. No significant effect of treatment was found (F = 3.79; DF = 1; P = 0.0 6 6). During separation period treated mares showed levels similar to basal values whereas in control mares 5-HT levels decreased. The sample size was small in this study. Further further studies with adequate sample sizes calculated to detect effects are necessary to evaluate if EAP, through 5-HT modulation, could help horses to cope with stress.