102 Influence of localized massage on biobehavioral responses of mature horses during exposure to unfamiliar stimuli

Abstract

Exposure to unfamiliar stimuli can lead to increased heart rate (HR), an increased incidence of locomotor behaviors, and changes in facial expressions. Responses of horses to unfamiliar stimuli can have important consequences for both horse and human safety. Horses preferentially groom conspecifics along the base of the neck, in front of the shoulder blade and across the withers. Imitated grooming of horses in this location has been shown to decrease horse HR. The objective of this study was to determine if localized massage along the base of the horse's neck and withers would influence HR, behavior, and facial expressions during exposure to an unfamiliar stimulus (cordless hair clippers) Eleven Quarter Horse mares (11.6 ± 4.9 yr) were fitted with a Polar H10 Equine HR monitor and led by the same handler to an open-front, 3.1 × 3.1 m grooming stall in a barn. After a 5 min acclimation period (P1: pre-stimulus), the clippers were turned on and held approximately 30.5 cm from the horse's left ear for a 3 min interval that consisted of: stimulus/pre-massage (45 s; P2), stimulus/massage (90 s; P3) and stimulus/post-massage (45 s; P4). The clippers were then turned off and the horse remained in the stall for 5 min (P5: post-stimulus). HR and video recording occurred throughout the 13 min session. Scan sampling of video footage every 15 s (P1 and P5) or every 5 s (P2-P4) was used to determine counts. Data wereanalyzed using PROC MIXED in SAS v. 9.4. Significant differences in HR, locomotor behaviors, and facial expressions were observed between horses in the study, highlighting the role of individual variation among horses. Although HR decreased once localized massage was initiated, no significant differences were observed in HR during exposure to the stimulus, with or without localized massage, compared with the pre- and post-stimulus periods. No differences were observed in the movement of horses’ front feet during exposure to the clippers; however, horses moved their hind feet more frequently during exposure to the clippers once the localized massage stopped (P < 0.05). Although the frequency of ears facing the same or different directions in a relaxed position was greater when localized massage was performed during exposure to the unfamiliar stimuli (P < 0.01), no differences were observed in nostril dilation, inner brow movements, or eye white increase during exposure to the stimuli compared with the pre- and post-stimulus periods. Localized massage may reduce stress-related behaviors during exposure of horses to unfamiliar stimuli; however, more research in this area is needed