“Dropping” in male horses during training: Part 2. Video observations

Abstract

Dropping (penile tumescence) in male horses has been related to the provision of food rewards but it is unclear why horses display this behaviour. The objective of this observational study was to characterize dropping in relation to other behavioural indicators. Trainers submitted videos of their training session with their horse (n = 24). Frequency of behaviours (oral, head position, tail swish), rewards (treats) and duration of penile characteristics (partial or full drop, flaccid or erect) were noted for multiple 2 min segments of the training session. Chi-squared analyses compared penile characteristics to rewards. A mixed model analyzed the effects of horse age and training segment on behaviours and penile characteristics. Dropping occurred 69 % of the time with either a flaccid or erect penis. In the first 2 min horses spent less time with a fully dropped and erect penis than later in the training session (p < .02). Horses 11–15 yrs were fully dropped (82 % of the time) and erect (65 % of the time) longer than older and younger horses (p < .0001). Horses spent less time fully dropped (15 %) when trainers did not use treats compared to when they did (42 %; p < .03). The number of dropping bouts did not differ regardless of whether treats were provided or not (p = .3672). Neither the use of touch (p = .6861) nor the use of the clicker (p = .3795) were related to dropping during training sessions. The horses exhibited shorter durations of being fully dropped (p = .0016) and fully erect (p = .0253) during afternoon training sessions compared to morning and evening training sessions. No stress-related behaviours (head positioning, tail swishing, lip licking) were related to dropping (p > .05) however lip licking did occur more frequently during the last two minutes of the session (p = .0003). From these observations it can be suggested that dropping is not a sign of stress but may relate to the affective state of the horse.