Measuring hoof slip of the leading limb on jump landing over two different equine arena surfaces

Synthetic surfaces containing polymer binders are less sensitive to moisture content because the binder helps surface cohesion but it is unclear how much polymer binder content influences hoof slip during limb landing. The objectives of this study were to compare hoof slip on two different surfaces and investigate relationships between hoof slip and surface properties. The leading right forelimb of six horses was recorded during jump landing on two different surfaces. A calibrated high speed camera (500 Hz) was used, positioned perpendicular to jump landing. Surface mechanical properties were measured for each horse. Horizontal displacement of the hoof reference marker was calculated, from impact to mid-stance as a measure of hoof slip. A significant difference in hoof slip was found between the two surfaces. Wax content appears to influence hoof slip during jump landing as greater hoof slip was measured on a 3% wax surface and variability on this surface was greater for the group.

Rationale

Surfaces play an important role for the performance horse in relation to injury reduction and locomotion efficiency and the ability of a surface to perform these two tasks relies on its functional properties. Excessive hoof slip on impact with a surface at high speed is known to be a common cause of soft tissue injury (Clanton et al., 1991) however some slip will help increase hoof deceleration and should therefore reduce limb loading and minimise mechanical stress related injury. Robin et al. (2009) highlighted that the functional properties of a surface will influence hoof slip and in jumping horses, Schamhardt et al. (1993) reported greater hoof slip in the leading forelimb during jump landing than in the trailing limb. Greater understanding of the effects of the surface on jump landing in the forelimbs would therefore be of benefit.

Objectives

The objectives of this study were to compare hoof slip on two different surfaces and investigate relationships between hoof slip and surface properties.

Methods

A contact mat and hoof reference marker were used to indicate the moment of impact and to provide a visible reference marker on the lateral hoof wall. The leading right forelimb of six horses was recorded during jump landing on two different surfaces. Five trials, plus one where the forelimb landed on a contact mat were recorded at 500 Hz using a calibrated high speed camera positioned perpendicular to landing. Horizontal displacement of the hoof reference marker was plotted and smoothed with a Butterworth filter at 25 Hz cut-off. Hoof slip was measured from impact to mid-stance. Mechanical properties of the surface were measured between horses using a Clegg impact hammer (surface hardness), a Longchamp penetrometer (penetrability) and a traction device, adapted from human sports turf assessments and modified with a studded horseshoe. Data were analysed using ANOVA and Pearson correlations.

Results

Mean hoof slip for all subjects on the 10% wax and 3% wax surface were 4.9±2.1 cm and 7.4±3.6 cm respectively. There was a significant difference in hoof slip between the 10% wax surface and the 3% wax surface (P<0.01). Greater hoof slip was found on the 3% wax surface compared to the 10% wax surface. There was a significant association between hoof slip and all surface measurements on the 10% wax surface but not on the 3% wax surface. Variation in hardness and traction was higher on the 3% wax surface than on the 10% wax surface.

Conclusion

The results suggest that wax content had an effect on surface properties and greater variability in hardness and traction on the 3% wax surface influenced the consistency with which the horses jumped.