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

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