Paired left-right asymmetries of the hoof surface in the Pyrenean Catalan yearlings are less marked among hindlimbs

Abstract

Most published researches that describe an equine hoof form are based on lineal and angular measurements. Here we apply geometric morphometric methods to study symmetries between fore and hind pairs in a pure horse breed. For this purpose, we studied a sample of 27 right-left pairs of distal limbs (12 forelimb and 15 hindlimb pairs) from young Pyrenean Catalan Horses ('Cavall Pirinenc Català'), a meat local breed from Catalonia (Spain), managed under semi-extensive conditions at NE Pyrenees. The outline of the hoof was represented by a set of 2 landmarks and 88 semi-landmarks, which were studied by means of geometric morphometric methods. Surfaces were similar for all limbs but significant shape variations appeared in fluctuating asymmetry, with less contra-paired differences in hindlimbs than between forelimbs. The detected asymmetry of the solar surface in this study may provide, in our opinion, and indicator of mechanical, not environmental, stress, as hooves, acting as robust but malleable pieces, can change shape according to pressure forces. So, if the hoof surface in the Pyrenean Catalan Horse exhibits asymmetry, it may be just a mere plasticity due to pressure forces. This asymmetry would be expressed less markedly in the hind pair, which represents the 'motor' part of the equine body and so, much linked to a perfect symmetrical functional performing.