Blood and salivary parameters for the assessment of the welfare of horses involved in therapeutic riding for children autism

INTRODUCTION: Therapeutic horseback riding (TR) may represent an innovative rehabilitative practice for children with autism spectrum disorders (ASD) (Borgi et al., 2016). However, the level of stress experienced by horses involved in TR needs special attention: horses are easily submitted to work stressors related to physical constraints and/or “psychological” conflicts, such as controversial orders from the riders or the requirement to suppress emotions (Hausberger et al., 2009). In this research project, the welfare of horses involved in TR was investigated combining several parameters: blood and salivary physiological markers are here presented and discussed. MATERIALS&METHODS: Data were collected from 17 healthy horses (mean age 17 years, mean BCS 6). Thirty-minutes TR sessions were carried out following a standardized protocol (Borgi et al., 2016), and each horse was ridden by a child with ASD and a typically-developed child (called respectively ASD and TD sessions). Ten minutes before (T0) and ten minutes after (T1) each session, salivary and blood samples were collected in order to assess salivary cortisol and α -amylases, blood cortisol, adrenocorticotropic hormone (ACTH), hematocrit (HCT), neutrophils (NEU), lymphocytes (LYM) and catecholamines (epinephrine, norepinephrine and dopamine). Non-parametric Wilcoxon signed- rank test and sign test were used to test the equality of matched pairs of observations (ASD vs TD sessions), while non-parametric Spearman correlation coefficient rho was calculated to evaluate correlation between quantitative parameters. Ethical approval from the Italian Ministry of Health was obtained. RESULTS: Significant positive correlations were found between salivary and blood cortisol (in T1 rho almost 0.52, p-value0.7 i.e. strong or very strong correlation; p-value<<0.05). The positive correlation between blood and salivary cortisol at T1 confirms salivary sampling as a possible non-invasive alternative to blood withdrawal, although it should be further investigated. In the comparison between ASD and TD sessions, the only significant differences among the above-mentioned parameters were higher NEU/LYM (sign test’s p -value=0.0592) and lower epinephrine found in ASD sessions (sign test’s p -value=0.0245). Since NEU/LYM ratio is likely secondary to catecholamine release and splenic contraction (Satué, Hernandez & Muñoz, 2012), these results could suggest a lower activation of the sympathetic nervous system (SNS) in horses ridden by children with ASD, whereas the activation of the hypothalamic-pituitary-adrenal (HPA) axis is not significant nor in T1 vs T0, neither in ASD vs TD. TAKE HOME MESSAGE: Analysis of blood and salivary parameters indicates that there is no difference in the activation of the HPA axis that is related to stress, comparing TD and ASD sessions. However, a lower SNS activation was found in horses during ASD sessions, suggesting a different SNS response to riders with different abilities. The experimental design of this research project will allow to go deeper -----------------------------------------------------Page 21-----------------------------------------------------  in the analysis of the mechanisms connected to the emotional response of horses involved in TR, including the evaluation of other parameters such as behaviour, heart rate variability and infrared termography data collected during different phases of the session as well as in relation to child-horse interaction. Aknowledgments. Funded by the Italian Ministry of Health, Ricerca corrente IZS VE 13/2013 “Riabilitazione equestre in bambini con disturbo dello spettro autistico: monitoraggio e valutazione del benessere animale”