Within riding lesson facilities, some individuals may assume that beginner riders place less strain on lesson horses than advanced riders due to reduced physical demands, however, this overlooks potential impacts on the horse’s affective state resulting from inconsistent or unrefined handling. This study investigated how rider level impacts the affective state of lesson horses during routine interactions. The Equine Facial Action Coding System (EquiFACS) was used to assess changes in facial expressions of lesson horses (n=35) before and after each horse participated in one beginner and one advanced hunter/jumper lesson. Video recordings (2-10 s) of the horse’s head were taken at five phases during a typical ride: before lesson preparation, post-saddling, post-bridling, immediately post-ride and post-untacking. A single, blinded, EquiFACS certified observer coded the presence of facial action units (FAUs) in the video clips. A Generalized Linear Mixed Model with repeated measures evaluated the effects of rider level, time, horse sex, years the horse has been in their current lesson program and the statistical interactions among these variables on the presence of FAUs, with effect estimates reported as odds ratios. All results are reported for tested effects, including non-significant results (p>0.05), to support transparent reporting. Rider level alone did not influence any FAU expression (all p>0.10), except for lips part (AU25; p=0.019); however, mares interacting with beginner riders were more likely to display full eye blinks (AU145; p=0.0021), half eye blinks (AU47; p=0.0018), lips part (AU25; p=0.037) and nostril lift (AUH13; p=0.0154) than with advanced riders. Nostril dilation (AD38; p=0.0185), nostril lift (AUH13; p=0.0103) and tongue show (AD19; p=0.0033) were more likely to occur in horses with 7 years experience. The sum of all FAUs (overall expressivity) declined after saddling (p=0.004) and oral-related FAUs continued to decline after bridling (AU16 lower lip depressor, p=0.004; AU25 lips part, p=0.0016; AU17 chin raiser, p=0.0016; AU24 lip presser, p=0.0194). Immediately post-ride, full eye blinks (AU145; p=0.0194), chewing (AD81; p =0.0435), ears forward (EAD101; p=0.0201) and eye white increase (AD1; p=0.0417) were more likely to occur than during bridling. Mares were more facially expressive overall than geldings (p=0.0002) and had higher odds of full and half blinks (AU145, p=0.0002; AU47, p=0.0068, respectively). These results suggest that rider level has a context-dependent influence on facial expressions, and some horses may display greater sensitivity to beginner riders. The most meaningful variation in facial expressions occurred across time phases, potentially reflecting pre-lesson anticipation and post-lesson relief or recovery. This information highlights the value of looking ‘behind the bridle’, as facial expressions may help riders and coaches monitor lesson-horse affective state and compatibility with the lesson program. • Lesson horses’ facial expressions vary across lesson time points • Rider level does not affect facial expressions in lesson horses • Lesson horses with less experience may be more sensitive to beginner riders • EquiFACS has potential to provide insights into equine affective states
Oberhammer et al. (Sun,) studied this question.