The Evolved Regulatory Repertoire: A Mechanistic Framework for Animal Welfare, with the Horse as a Worked Example

Animal welfare science identifies physical, environmental and behavioural conditions associated with animals' subjective experiences, but lacks a single organism-level account of why these conditions matter and how their effects are integrated. This Horizon Topic proposes the Evolved Regulatory Repertoire (ERR): the integrated behavioural, physiological, cognitive, affective, endocrine, immune and developmental systems shaped by selection to support organismal regulation. Welfare is proposed to emerge through the temporal integration of regulatory success and failure as a sentient organism, given its capacity and environmental opportunity, exercises its biologically relevant repertoire. Capacity and opportunity enable regulatory activity but do not themselves constitute welfare. The account treats behaviour as organism–environment regulation, affect as both a control signal and an experiential source of information about regulatory trajectory, and chronic compromise as persistent failure to resolve biologically important demands. The ERR integrates, rather than replaces, coping, allostasis, behavioural-needs, controllability, agency and affect-based accounts. Its distinctive emphasis is that environmental opportunity varies independently of organismal capacity and must be specified without reference to the welfare outcome it predicts. Nine predictions are presented, including tests of whether welfare effects depend on the independently established biological centrality of the regulated system and whether ERR variables add predictive value beyond established indicators. The framework redirects assessment from inventories of resources or behaviours towards whether animals can successfully regulate through contingent interaction, and provides a research programme for developing independent, species-relevant measures of opportunity and regulatory outcome. Author's manuscript as submitted for peer review (Horizon Topic). Not peer reviewed.