Inducing and measuring positive affective state in domesticated equines: A Delphi consultation.

Over the last twenty years the definition of good animal welfare has advanced from the 'absence of negative welfare states' to the aim of identifying the presence of positive welfare states; however, research on positive animal welfare is relatively new. Consequently, through expert consultation, this study aimed to synthesise knowledge regarding domesticated equine emotional state, specifically methods to induce and measure positive affective states, which could be of significant benefit to equine welfare across sectors. A Delphi consultation of experts in the field of equine behaviour, welfare and affective state was undertaken to derive consensus agreement on definitions used when considering positive affective state in equines and methods suitable for inducing and measuring these states within experimental investigations. Ninety-three international experts participated in a robust three-round Delphi consultation with data gathered analysed qualitatively (thematic analysis) and quantitatively (ranking data, consensus benchmarks and Content Validity Index (CVI) / Content Validity Ratio (CVR) analyses). Retention rates were high (78 %), and consensus (minimum 70 % agreement) was reached within Round three of the consultation. Nineteen methods for inducing positive affect reached consensus (provision of high value food, an affiliative companion and a substrate to roll in where the highest ranked), and twelve behavioural (assessment of body language, facial actions and horse-horse interactions were ranked highest) and three physiological (evaluation of heart rate, heart rate variability and respiratory rate) variables for measuring positive affect also reached consensus. This consultation highlights several important considerations surrounding the induction and measurement of positive affective state in equines, including consideration of the individual's personality and individual preference within any measures of affective state. We therefore recommend that establishing individual preference should be a prerequisite of research into positive affective states. It is anticipated that the results of this study can be used to provide new direction for research on positive affective states by providing expert agreed methods and measures for policy and practice through expert agreed approaches to induce positive affect in horses.