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

This study gathered expert consensus on how to create and detect positive emotions in domesticated horses using a structured three-round Delphi process. It prioritizes methods to induce positive affect and the behavioral and physiological indicators to measure it, emphasizing the need to tailor approaches to each horse’s preferences and personality.

Background and Rationale

• Animal welfare science has expanded from preventing negative states to actively promoting positive experiences, but equine-specific evidence remains limited.
• Consolidating expert knowledge can speed progress across sectors that manage horses (sport, leisure, therapy, working equids) by identifying practical, welfare-enhancing methods.

Objectives

• Reach consensus on definitions relevant to positive affective state in domesticated equines.
• Identify, prioritize, and validate methods to induce positive affect and indicators to measure it for use in research and practice.

Study Design: Delphi Consultation

• Participants: 93 international experts in equine behavior, welfare, and affective science.
• Process: Three iterative survey rounds with feedback between rounds; strong participant retention (78%).
• Consensus: Achieved by Round 3 using a predefined threshold (minimum 70% agreement).
• Analyses: Mixed-methods approach combining qualitative thematic analysis with quantitative rankings and content validity statistics (Content Validity Index, Content Validity Ratio) to judge relevance and essentiality of items.

Consensus: Inducing Positive Affective States

• Total: Nineteen methods to induce positive affect reached consensus.
• Highest-ranked inducers:
  • Provision of high-value food (e.g., especially palatable or preferred feeds).
  • Access to an affiliative companion (compatible social contact).
  • Availability of a substrate to roll in (e.g., sand, soil, suitable bedding).
• Cross-cutting principles emphasized by experts:
  • Match inducers to the individual horse’s preferences and personality traits.
  • Provide choice and controllability to strengthen positive appraisal and avoid frustration.
  • Avoid confounding factors (e.g., novelty-induced arousal that may not reflect positive affect).

Consensus: Measuring Positive Affective States

• Behavioral indicators (12 reached consensus); top-ranked categories:
  • Structured assessment of body language and posture.
  • Assessment of facial actions.
  • Observation of horse–horse interactions.
• Physiological indicators (3 reached consensus):
  • Heart rate (HR).
  • Heart rate variability (HRV).
  • Respiratory rate.
• Measurement guidance from the panel:
  • Combine behavioral and physiological data to increase validity and interpretability.
  • Use repeated measures within individuals to account for baseline differences.
  • Control for context and confounders (e.g., exercise load, ambient temperature, time of day).

Definitions and Scope

• Experts reached agreement on key terms related to positive affect in horses, creating shared language for future studies (exact wording not provided in the abstract).
• Focus on experimental applicability while informing everyday welfare practices and policy development.

Analytical Approach and Validity

• Thematic analysis distilled rationales, caveats, and contextual considerations supplied by experts.
• Ranking data produced prioritized lists of inducers and indicators to guide resource allocation and protocol design.
• Consensus benchmarks (≥70% agreement) ensured only broadly supported items advanced.
• CVI and CVR quantified item relevance and essentiality, strengthening the content validity of the final recommendations.

Key Findings

• Expert-backed toolkit: A consolidated set of methods to induce positive affect and indicators to measure it in horses.
• Top inducers: High-value food, affiliative companionship, and access to rolling substrates.
• Top measures: Behavioral focus on body language, facial actions, and social interactions; physiological focus on HR, HRV, and respiratory rate.
• Individualization is essential: Establishing and integrating individual preferences and personality is a prerequisite for valid assessment.

Implications for Practice and Policy

• Management routines can incorporate consensus-backed inducers (e.g., compatible social housing, rolling areas) to promote positive states.
• Welfare monitoring should include structured behavioral observation plus feasible physiological metrics where possible.
• Policy and accreditation schemes can move beyond minimum standards to require opportunities for positive experiences and choice-based enrichment.
• Training and handling can leverage preferred rewards and respect individual variation to foster positive affect during learning.

Implementation Suggestions

• Preference assessment:
  • Conduct brief, repeated choice tests to identify preferred foods, social partners, and enrichment options for each horse.
  • Reassess preferences periodically to capture changes over time or context.
• Measurement plan:
  • Establish individual baselines for HR, HRV, and respiratory rate at rest and in standardized low-arousal contexts.
  • Use structured ethograms and inter-observer reliability checks for body language and facial actions.
  • Time observations to minimize confounds (e.g., avoid periods immediately before routine feeding or turnout).
• Ethical safeguards:
  • Design control conditions that do not entail deprivation or induce negative states.
  • Offer choice and the ability to opt out to maintain voluntariness and positive valence.

Strengths and Limitations

• Strengths:
  • Large, international expert panel with high retention across rounds.
  • Robust triangulation of qualitative insights and quantitative validation (rankings, CVI, CVR, consensus thresholds).
• Limitations:
  • Findings reflect expert consensus rather than direct experimental validation of efficacy or diagnostic accuracy.
  • Only the top-ranked inducers and indicators are specified in the abstract; full lists require consulting the full paper.
  • Despite breadth, panel composition may still carry disciplinary or regional biases.

Future Research Directions

• Empirically test sensitivity, specificity, and reliability of the agreed indicators in controlled and field settings.
• Develop standardized, user-friendly tools and scoring protocols for body language and facial action assessment.
• Quantify moderating effects of individual differences (e.g., age, breed, sex, training history, temperament) on responses to inducers.
• Evaluate feasibility, cost, and welfare outcomes when implementing the consensus toolkit across sectors.
• Investigate additional noninvasive physiological or neurobiological markers that are practical in real-world contexts.

Bottom Line

• This Delphi study delivers prioritized, expert-endorsed methods to create and detect positive emotions in horses and underscores that establishing each horse’s preferences should precede assessment—providing actionable direction for research, practice, and policy.