The Relationship Between Fluctuating Asymmetry and Performance in Event Horses

Description

REASONS FOR PERFORMING STUDY: Symmetry of biological bilateral traits is the optimal aim during growth and development of an organism (Thornhill and Gangestad 1994; Manning and Pickup 1998) and has been suggested to act as an indicator of phenotypic quality within a number of species (Manning et al., 1996). The symmetry of bilateral morphological traits has been linked to superior athletic function in both humans (Manning and Pickup 1998) and racehorses (Manning and Ockenden 1998). The relationship between asymmetry and performance within other equine disciplines has yet to be investigated and may act as future indicator of performance potential in youngstock if found to be a cross-discipline performance characteristic.HYPOTHESIS: A significant difference exists between the symmetry of advanced event horses and horses that have failed to reach advanced level eventing.METHODS: Direct measurements of 15 bilateral traits were taken from 18 event horses (mixed age and gender) that had competed and gained points at advanced level during the previous 2 years and 15 horses of (mixed age and gender) that had been bred with the primary purpose of eventing but proven incapable of progressing further than novice or intermediate level. Nostril and pinna length and width, fore and hind proximal phalanx (FPP, HPP), third metacarpal (MCIII) and third metatarsal (MTIII) length and width, carpal width and circumference and tarsal width were measured via Invicta callipers (mm) (1mm accuracy). Anatomical landmarks were confirmed as giving repeatable measurements during a pilot study. Three repeated measurements were taken by the same operator and the mean calculated. Absolute fluctuating asymmetry (FA) for each of the bilateral traits was calculated by subtracting the smaller measurement from the corresponding larger measurement. No identification of ‘sidedness’ was therefore made. The Mann Whitney u test (5% significance) was used to test for any differences between the two study groups for the traits measured.RESULTS: The results demonstrated a statistically significant (p≤0.05) lower FA within the elite group for the traits of pinna length and width, MCIII width and carpal circumference. Highly significant (p≤0.01) differences were identified for the traits of nostril length and third metacarpal length and for the mean total asymmetry score for the two groups (advanced = 0.145 ± 0.013; control = 0.254 ± 0.008)CONCLUSION AND CLINICAL RELEVANCE: The results reinforce previous research findings indicating that the elite equine athletes demonstrate a much lower trait asymmetry. These findings could be used to identify potentially superior equine athletes at a younger age and could also be furthered to identify any association with injury prevalence. REFERENCES: Manning, J.T., Scutt, D., Whitehouse, G.H., Leinster, S.J. & Walton, J.M. (1996) Asymmetry & the menstrual cycle in women. Ethol Sociobiol 17: 129-143Manning, J.T. & Pickup, L.J. (1998) Symmetry and Performance in Middle Distance Runners. International Journal of sports Medicine 19: 205-209Manning, J.T. & Ockenden, J. (1994) Fluctuating asymmetry in racehorses Nature 370:185-186Thornhill, R. & Gangestad, S.W. (1994) Human fluctuating asymmetry and sexual behaviour. Psychological Science 5(5): 297-30

Period	Jun 2008
Event title	International Conference on Equine Locomotion 2008
Event type	Conference
Conference number	6
Location	Normandy, FranceShow on map