Effects of Poll Flexion on Breathing and Behaviour

Increasing poll flexion, at least in the ranges seen in top-performing dressage and sport horses, makes it harder for the horses to breathe.
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Effects of a 15° Variation in Poll Flexion during Riding on the Respiratory Systems and Behaviour of High-Level Dressage and Show-Jumping Horses
Animals (Basel). 2023 May 22;13(10):1714.
Authors
Paula Tilley 1 2 , Joana Simões 1 2 3 , José Paulo Sales Luis 1 2
Affiliations

1 Centre for Interdisciplinary Research in Animal Health (CIISA), Faculty of Veterinary Medicine, University of Lisbon, Av. Universidade Técnica, 1300-477 Lisbon, Portugal.
2 Associate Laboratory for Animal and Veterinary Sciences (AL4AnimalS), 5000-801 Lisbon, Portugal.
3 Equine Clinical Academic Department, Faculty of Veterinary Medicine, Lusófona University, 1749-024 Lisbon, Portugal.

PMID: 37238147
DOI: 10.3390/ani13101714

Abstract

From previous studies, the International Society for Equitation Science has advised that further research be conducted on the physiological/psychological effects of less-exacerbated poll flexion angles. We aimed to evaluate the effects of two riding poll flexion positions with a difference of only 15° on the respiratory systems and behaviour of horses through an evaluation of dynamic airway collapse via over-ground endoscopy, the pharyngeal diameter, pleural pressure, arterial oxygenation and lactate, HR/RR, and the occurrence of conflict behaviours. Twenty high-level dressage and twenty show-jumping horses underwent a 40 min ridden test at a ground angle of 85°; 3 weeks later, they underwent a ridden test at a 100° ground angle (the angle between the ground and the line from the forehead to the muzzle) and in a cross-over design. Using a mixed model for repeated measures, Wilcoxon/Friedman tests were carried out according to the experimental design and/or error normality. For both groups, at 100°, conflict behaviours and upper airway tract abnormalities were significantly more frequent, and the pleural pressure was higher, and the pharyngeal diameter was lower. At 85°, relaxation behaviours were significantly more frequent. Lactate was significantly higher at 100° only in the dressage horses. Compared to the first test at 85°, the HR/RR were significantly lower at the beginning of the second test (at 100°) but higher at the end. The significant differences identified in these dressage and show-jumping horses support the idea that an increase of just 15° in riding poll flexion can have negative effects on the respiratory system and behaviour of a horse and therefore on its welfare.

Keywords: conflict behaviour; dressage; over-ground endoscopy; show jumping; upper airways.

Conclusion
Based on the substantial number of studies previously conducted on the impact of hyperflexion on horse welfare, the ISES advised in a position paper for further research to be carried out on the physiological and psychological effects of lesser degrees of poll flexion and extension, which was the reason for the present study to be undertaken.
When testing this group of dressage and show-jumping horses with the 100°-ground-angle poll flexion positions, in comparison to the 85° poll flexion position, multiple upper airway dynamic dysfunctions were significantly more frequent, and the highest scores were attributed to nasopharyngeal collapse, palatal instability/dysfunction, and intermittent bilateral arytenoid cartilage collapse. In addition, most conflict behaviours were significantly more frequent at this poll flexion angle, with the highest scores attributed to excessive salivation (drooling), mouth opening, and turning the ears backward. On the other hand, it is also noteworthy that relaxation behaviours were significantly more frequent with the 85°-ground-angle poll flexion position, and the highest scores were attributed to turning the ears forward and ear play (ear movement). Although upper airway dysfunctions and conflict behaviours were more often associated with the more-flexed poll position, their effect on dressage and show-jumping horses’ performance and welfare must be further evaluated.
Furthermore, the pharyngeal diameter at the 100°-ground-angle poll flexion position was even smaller than the values previously reported in the literature, which probably contributed to the significantly higher pleural pressure (ΔPpl) also found with this more-flexed poll angle. This could have been influenced by neck conformation. Depending on their anatomical conformation, different horses may have more or less difficulty bending their neck and poll. Therefore, additional research is necessary to assess the relevance of neck conformation for different equestrian disciplines.
The most significant differences between the equestrian sports evaluated in the present study, dressage and show jumping, refer to the conflict and relaxation behaviours, as there were no significant differences in this respect for the upper airway dynamic dysfunctions. The fact that it was possible to discriminate between the two riding poll flexion positions based on a few conflict behaviours and a few relaxation behaviours could contribute to an easier detection of discomfort in the ridden horse.
Overall, the significant differences identified here for various parameters (the occurrence of upper airway dynamic dysfunctions and conflict behaviours, pharyngeal diameter, pleural pressure, and HR and RR) between two very close head and neck positions in the ridden horse support the idea that a variation of as little as 15° in poll flexion can have negative effects on the horses’ respiratory systems and behaviour and therefore on the horses’ welfare. We believe that the relevance of keeping the amount of time spent riding with a poll flexion ground angle greater than 85° to an essential minimum should be further explored for the benefit of horse performance and the horse’s quality of life in sport, thereby reassuring public concern.