A novel behaviour-based stress score for donkey – horse hybrids during restraint

Donkey – horse hybrids (mules and hinnies) are amongst the least studied equids, with much of the existing knowledge about their behaviour based on anecdotal experience. Hybrids display behavioural traits of both parent species, which may lead to misinterpretation of behaviour and escalation towards aggression when stress levels are high. A method of interpreting levels of stress via behavioural indicators would therefore be beneficial to improve hybrid welfare and human safety, especially during veterinary procedures. Drawing on existing ethograms and pain indicators for horses and donkeys, we developed and assessed the inter-observer reliability of a behaviour-based escalating stress score for hybrids whilst inside a handling unit. A cohort of trained handlers assessed 20 hybrids during initial testing, and 50 hybrids following refinement of the scoring system. Interobserver reliability increased from moderate (ICC=0.74, 95% CI=0.62–0.84) to good (ICC=0.78, 95% CI=0.72–0.83) following refinement. This score will be beneficial for better understanding this under studied equid and could help improve hybrid welfare during training and for veterinary procedures.