A note on the habituation to novelty in horses: handler effect

Abstract

The intensity with which the horse reacts to novelty is crucial for safety of both horse and human. The aim of the study was to examine: (1) whether horses’ fear reactions to a startling novel object diminish with successive test days and (2) whether the active human handling leads to the decrease of the fear-related responses of the horse. Eight adult horses were submitted daily to 5-minutes exposition to a novel object (NO) – open umbrella – for 5 consecutive days when released (Trial 1) and for 5 consecutive days when held by the handler (Trial 2), with 2-days break between Trials. Startle reaction score (SR), latency to touch the novel object (LNO), mean heart rate (HR) during 6 minutes of the tests, the percentage of time the horse spent standing, on locomotor activity (walk, trot, gallop) or on vigilance (vigilant standing, sustained walk) were analysed. The SR and LNO during Trial 1 did not change in consecutive test days. The NO provoked higher HR (P<0.05 ) and intense vigilant standing at the beginning of the study (P<0.01). Per cent of time of sustained walking, standing, trotting and galloping did not differ between days during Trial 1. The SR during Trial 2 differed neither within nor between Trials. The horses approached NO when handled as compared to almost no approach when not held by the handler (P<0.05). With each day of the Trial 2 the horses approached quicker the umbrella (P<0.05). The HR was lower than in the