A preliminary investigation which indicates the use of forelimb data has limitations in accurately determining laterality in horses

Side preference is suggested to link with cognitive bias and the phenomenon of laterality is proven in a range of species, including the horse. Motor lateralisation refers to directional bias; in equine research this has been measured using the favoured fore limb during the initiation of movement or the advanced fore limb during grazing. However little has been done to validate the links between forelimb observations and side preference, for example the hind limb in most cases initiates movement. Two preliminary studies were conducted; the first aimed to identify whether a correlation existed between fore and hind limb preference, the second aimed to consider whether kinematic measurements of the stabilising and mobilising limb correlate with the preferred limb which is used to indicate laterality. Statistical analysis in both pilot studies was not possible due to the small sample populations. In the first study, six horses (various breed/sex, mean age 10.3 years +5.5) were released ten consecutive times to navigate towards a feed bucket in an enclosed arena. Frequency data were collected from observations of the hind limb used to initiate movement and fore limb advancement; laterality index scores (equation from McGreevy and Rogers, 2005) were calculated. The left hind limb was used to initiate movement during 43% of observations. Laterality index for hind limb indicated a right limb preference (13.33). The left forelimb was advanced whilst eating from the bucket for 51% of observations. Laterality index for forelimb indicated a slight left limb preference (-1.69), in opposition to the hind limb result. In the second study, horses were observed whilst eating a forage ration from the floor to establish limb preference using the laterality equation from the first study; these individuals then underwent a conformational assessment to discount participants with conformational asymmetries. Four horses (two mares, two geldings, mean age 18 +2.8 years) were selected for kinematic analysis; skin markers were attached to correspond with the centres of rotation for the major joints of the appendicular skeleton and horses were then trotted in hand past a Casio high speed video camera placed 10m away from the plane of motion. Three passes in each direction were made for each individual. Measurements of mobilising and stabilising limb traits were averaged from the three runs on each side, but no clear links were recorded between these traits and the advanced forelimb used to determine laterality. Results from these preliminary studies suggest that hind limb preference is not matched by forelimb preference. Further study is required to determine links with lateralisation.