Serotonin, BDNF, and Oxytocin Plasma-Saliva Relationships Fail to Correlate with Equine Temperament After Correction

Assessing equine welfare is crucial for effective management, training, and safety, yet objective and reliable indicators remain a challenge. Traditional stress markers like cortisol often exhibit high variability and context dependency, limiting their utility as standalone measures of a horse's emotional state. There is a growing need for more comprehensive biomarkers that can provide nuanced insights into well-being. Serotonin, brain-derived neurotrophic factor (BDNF), and oxytocin are neurohormones and growth factors known to influence mood, social behavior, and stress responses across species, making them promising candidates for a more holistic assessment of equine welfare.

Researchers evaluated the plasma-saliva relationships for cortisol, oxytocin, and serotonin in 40 horses. The study aimed to explore potential associations between these biomarkers and various temperament traits. Blood and saliva samples were collected from the horses, and the concentrations of the target biomarkers were quantified using enzyme-linked immunosorbent assays (ELISA). Additionally, the horses were categorized based on their level of human handling (regular vs. minimal) to investigate potential group differences in biomarker profiles. The primary analytical approach involved assessing correlations between biomarker levels and temperament, with a critical step of applying statistical correction for multiple testing.

Initial unadjusted analyses revealed several nominal associations between the measured biomarkers and the assessed temperament traits. However, after applying rigorous statistical correction for multiple testing, > none of these observed associations remained statistically significant. This indicates a lack of robust correlation between plasma or salivary levels of cortisol, oxytocin, and serotonin and the temperament traits evaluated in this N=40 equine cohort. While unadjusted data suggested that horses with regular human handling exhibited trends for lower cortisol and higher oxytocin concentrations compared to minimally handled horses, the abstract implies these between-group differences also did not achieve statistical significance after correction, aligning with the overall conclusion of no robust findings.