Auditory enrichment on facial and physiological responses of Pantaneiro geldings and mares under short-term stress.

This study aimed to evaluate the effect of auditory stimuli on mares and geldings during social isolation and movement restriction, and their ability to promote the reduction of stress responses. The research was conducted with eight Pantaneiro horses, divided into Experiment I (4 mares) and Experiment II (4 geldings), both experiments were executed equally using a 4x4 Latin square design with experimental (classical, country and new age) and control (no music) treatments. Physiological parameters (heart rate, heart rate variability, respiratory rate, ocular temperature by infrared thermography, and surface temperature by infrared thermometer) and facial expressions (eye closure (AU143), blink (AU145), half blink (AU47), inner brow raiser (AU101), eye white increase (AD1), tongue show (AD19), nostril dilator (AD38), chewing (AD81), ears forward (EAD101), and ear rotator (EAD104)) were assessed throughout the 24 minutes that the animals remained in the restraining stock. In Experiment I, there was a reduction (p < 0.05) in heart rate during classical and country treatments and an increase (p < 0.05) in auricular and body temperatures during the classical treatment. Additionally, the frequencies of expressions of nostril dilator (AD38), ear rotator (EAD104), and half blink (AU47) were lower (p < 0.05). In Experiment II, there was an increase (p < 0.05) in ocular temperature during the country and control treatments, and a higher frequency (p < 0.05) of ears forward (EAD101) during the country treatment. Exposure to Beethoven's 9th Symphony (classical genre) and Hank Williams Jr.'s "Ramblin' In My Shoes" (country genre) reduced stress in mares. Geldings showed less pronounced responses to music genres, indicating a possible preference for Janet Marlow's "Horsing Around" (new age genre). Music can be used as auditory enrichment for horses in the specific context of this study.