IMAGING AND REHABILITATION Definitive differentiation between pain or discom-


fort induced by tack and other innate behavioral reasons cannot be made on the basis of these stud- ies. When a horse is learning a new movement, it may misunderstand the rider’s cues or find it phys- ically difficult due to the unaccustomed use of spe- cific muscle groups, which may result in delayed onset muscular stiffness.54,55 Conflict behavior56 or resistant behavior may be displayed, but persis- tence of such behaviors would not be expected unless there was an underlying pain-related problem. Recognition of changes in behavior facilitates recog- nition of improvement in performance and willing- ness to work following improvement or resolution of pain causing lameness using diagnostic anesthesia. The persistence of 8 or more of the 24 behaviors of the Ridden Horse Pain Ethogram is likely to indi- cate residual musculoskeletal pain, requiring fur- ther investigation. The Ridden Horse Pain Ethogram was developed


Fig. 6. The horse is spooking, not following the rider’s cues. The tail is swishing.


duce nosebands, such as a crank noseband with a flash or to tighten nosebands rostral to the bit. Although saddle fit did not significantly influence behavior scores in one study,40 an ill-fitting saddle does have the potential to induce abnormal behav- iors, which disappear if a better fitting saddle is used.


There are a number of additional features that


have not been assessed objectively but that are of potential clinical relevance during ridden exercise: teeth grinding, abnormal breathing noises, grunt- ing, and sweating disproportionate to the level and amount of work, fitness, and environmental temper- ature. There are features that may be felt by a rider: episodic shooting forwards, absence of rein tension (not taking a contact), symmetrically in- creasing rein tension (hanging on the reins), asym- metrical rein tension (hanging on one rein more than the other), reduced range of motion of thoraco- lumbosacral region (“back stiffness”), tension, lack of hindlimb impulsion, and being on the forehand. There are also features of gait that are difficult to reliably measure without high-speed video, such as alterations in canter (e.g., temporal and spatial sep- aration of the hindlimbs during the stance phase). Assessment of blink rate was not performed but may be useful for future studies. Increased blink rate has been linked positively to the amount of dopa- mine in the basal ganglia of the brain,52 and dopa- mine levels may increase as a result of pain.53


340 2020  Vol. 66  AAEP PROCEEDINGS


in sports horses used in the Olympic disciplines in which the horse is expected to work with the front of the head in a vertical position, on the bit, when performing schooling-type work. However, other than head position, the ethogram is readily trans- ferable for other types of work (e.g., jumping), when working individually, although close proximity of other horses may influence behavior.


8. Conclusions


It is concluded that the demonstration of 8 or more of the 24 behaviors of the Ridden Horse Pain Etho- gram is highly likely to reflect the presence of mus- culoskeletal pain in sports horses, although some lame horses score less than 8. It is considered im- portant that those interacting in any way with or responsible for horses are educated about the signs that may reflect pain when horses are ridden (e.g., ears back, mouth opening, tongue out, change in eye posture and expression, going above the bit, head tossing, tilting the head, unwillingness to go, crook- edness, hurrying, changing gait spontaneously, poor quality canter, resisting, and stumbling and toe dragging). If changes in body postures and resistance to following commands could be used to alert riders of potential pain, then the welfare of horses could be significantly improved. Horses would not fall victim to harder training practices that could further aggra- vate musculoskeletal pain or to a punishment-based training regimen to address the animal’s unwilling- ness to follow commands of the rider.


Acknowledgments


Several of the studies were generously supported by World Horse Welfare. The Saddle Research Trust also contributed. The sponsors had no role in any aspect of the studies. Co-authors of the studies were Jeannine Berger, Anne Bondi, Andrea Ellis, Jessica Mullard, Laura Quiney, Katy Thomson, and Jan Van Dijk.


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