OBJECTIVE AND HYPOTHESIS Acclimation of Mature Horses to Novel Short-Term Confinement and Social Isolation Cheryl R. Hansen1, Ashley L. Wagner2, and Rebecca K. Splan1 1Department of Animal Science, Sul Ross State University, Alpine, TX, USA; 2Probiotech International LLC, Saint-Hyacinthe, Canada INTRODUCTION RESULTS Sudden confinement and social isolation can be stressful to naïve horses, resulting in an increased incidence of locomotor and anxiety-related behaviors (Visser et al., 2008). These types of stressors, while generally common in the horse industry, may compromise physical or mental well-being in the short term (Stull and Rodiek, 2000). Figure 1. Plasma cortisol concentration at baseline and 30 min into the stall isolation test. Plasma cortisol levels increased during the isolation test but were reduced in the second exposure. Figure 2. Anxiety and frustration related behavior exhibited during the first and second 30 mins of the stall isolation test. Fewer steorotypies were exhibited during the second half of the test and during the second exposure. OBJECTIVE AND HYPOTHESIS The objective of this study was to investigate how mature stock-type horses acclimated to two 60-min episodes of a novel stall confinement and social isolation test. It was hypothesized that horses would display fewer locomotor- and anxiety-related behaviors as the test progressed, and that measures of stress would also decrease with repeated exposure to the test. Figure 3. Anxiety and frustration related behavior as a percent of time budget. Horses spent a greater amount of time displaying anxiety-related behaviors during the first, relative to the second, 30 min of the stall isolation test. Figure 4. Heartrate during first and second interval of stall isolation test. Heart rate increased during test relative to baseline with no significant difference noted between exposures. MATERIALS AND METHODS 10 mature stock-type horses (mean age 8.7 ± 1.7 yr, mean weight 480 ± 25 kg) acclimated to two 60-min episodes of a novel stall confinement and social isolation test. Horses were placed in a center-aisle-facing, 3.5 x 3.1 m cinderblock stall with a cross-mesh front and rubber mat flooring. No visual stimuli of human or horse activity were provided during the 60-min episode. No hay, water, or bedding was provided during the stall isolation test. One week after each horse was initially subjected to the stall isolation test, the test was repeated. Horses were videotaped using a commercial digital recorder located in the stall across the aisle. Heartrate was recorded 30 min before, 30 and 60 min into the test, and 30 min after the horse was returned to its paddock. Blood was collected and plasma cortisol was analyzed prior to, and 30 min into, the stall isolation test. Scan sampling of video footage every 20 sec was used to construct a time budget for each horse. Counts of stereotypies and anxiety- or frustration-related behaviors were recorded. Data were analyzed using a Friedmans chi-square test. DISCUSSION Owners and trainers should consider the physiological effects of exposing naïve horses to novel confinement or isolation. Horses adapted relatively rapidly with respect to time and repeated exposures; when seeking optimal performance these outcomes should be considered. Horses expressed differences in anxiety -related behaviors but remained consistent within individual. REFERENCES Stull, CL and Rodiek, AV. 2000. Physiological responses of horses to 24 hours of transportation using a commercial van during summer conditions. J Animal Sci 78(6): 1458-1466. Visser, EK, AD Ellis and CG Van Rennen. 2008. The effect of two different housing conditions on the welfare of young horses stabled for the first time. Appl Anim Behav Sci 114(3-4):521-533.