Straw-enriched bedding enhances behavioural indicators of positive welfare but not behavioural synchrony in individually housed horses

Contemporary animal welfare research increasingly emphasises positive welfare, focusing on animals’ opportunities to express species-typical behaviours that reflect engagement with their environment rather than solely the absence of negative states. In individually housed horses, environmental enrichment is widely applied, yet its contribution to behavioural expression associated with positive welfare and the temporal organisation of behaviour remains insufficiently understood. This study investigated whether bedding enrichment, achieved by adding straw to pine shavings, influences behavioural patterns and behavioural synchrony in individually housed horses. Ten Lipizzan horses were housed in individual boxes and assigned to either a control condition with pine shavings (n = 5) or a straw-enriched condition (n = 5). Behaviour was recorded during four overnight observation periods (16 h each). Fourteen event and state behaviours were analysed using regression-based approaches, non-parametric tests, and correlation analyses to evaluate individual behavioural patterns and synchrony among horses. Straw-enriched bedding significantly increased behaviours involving active interaction with the substrate, particularly bedding manipulation (p < 0.001), and increased body care behaviour (p < 0.01), while urination and defecation occurred less frequently (p < 0.01). Horses housed on straw-enriched bedding spent more time resting while standing (p < 0.001), whereas total resting time was reduced (p < 0.001)