Relationship Between Magnitude and Direction of Asymmetries in Facial and Limb Traits in Horses and Ponies.

The research article explores the relationship between the size or magnitude of asymmetries in different parts of horses and ponies’ bodies and their root cause. The article shows that this asymmetries closely resemble ones observed in humans and other animals, suggesting similar measurement criteria might be useful in treating and preventing injury in these animals.

Objective of the Study

• The main objective of the study was to examine the relationship between the size or magnitude of asymmetries in non-elite horses and ponies, particularly in their faces and limbs, and their root cause. The research also sought to compare these findings with asymmetries previously observed in racehorses.

Methodology of the Research

• The researchers had taken direct measurements of 15 bilateral traits (two-sided traits) divided into four facial and 11 limb traits on a sample size of 100 horses and ponies.
• The overall population sample was divided into two groups based on the measurements of their withers height. Those exceeding 148 cm were classified as horses, and those equal or below 148 cm were categorized as ponies.
• Each group was then subdivided based on whether the animals had larger left or right-side traits. The asymmetries were then compared as mean asymmetries, and the percentages of the trait size at each grouping level.

Key Findings of the Study

• The size of the asymmetries measured largely reflected previously recorded asymmetries related to each trait. This suggests that the asymmetries were probably inherent rather than caused by external factors.
• Both the horse and pony groups had significantly longer third metacarpal (hand bone) and third metatarsal (foot bone) on the right side. In the horse group, the left forelimb’s proximal phalanx (the bone at the base of the fingers or toes) was longer and wider than the right.
• This pattern mirrors the biomechanical preference for a left-lead anticlockwise canter that was previously only observed in racehorses. This suggests that the proximal phalanx of the forelimb might be compensating for the higher loading forces associated with the lead forelimb.
• When the asymmetry sizes were scaled as percentages of trait size, they were found to closely match those reported in humans. This suggests that similar measurement criteria could be used in mitigating or preventing injuries among horses.