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Davies, H. M. S. (2005). The timing and distribution of strains around the surface of the midshaft of the third metacarpal bone during treadmill exercise in one Thoroughbred racehorse. Aust Vet J, 83(3), 157–162.
Abstract: OBJECTIVE: To confirm that the midshaft dorsal cortex of the third metacarpal bone experienced higher compressive strains during fast exercise than the medial or lateral cortices, and that the strain peak occurred earlier in the hoof-down phase of the stride on the dorsal cortex than the medial or lateral cortices. DESIGN: Observations of a single horse. PROCEDURE: Strains were collected from a single, sound, 3-year-old Thoroughbred mare during treadmill exercise from rosette strain gauges implanted onto the medial, lateral and dorsal surfaces of the midshaft of the right cannon bone, simultaneously with data from a hoof switch that showed when the hoof was in the stance phase. RESULTS: Peak compressive strains on the dorsal surface of the third metacarpal bone were proportional to exercise speed and occurred at about 30% of stance. Peak compressive strains on the medial surface of the non-lead limb reached a maximum at a speed around 10 m/s and occurred at mid-stance. Peak compressive strains on the lateral surface varied in timing and size between strides at all exercise speeds, but remained less than -2000 microstrains. CONCLUSIONS: The timing of peak compressive strains on the dorsal cortex suggests a relationship to deceleration of the limb following hoof impact, so the main determinants of their size would be exercise speed and turning (as shown in previous experiments). This experiment confirms data from other laboratories that were published but not discussed, that peak compressive strains on the medial surface occur at mid-stance. This suggests that they are related to the support of body weight. The strains on the lateral cortex occurred at variable times so may be associated with the maintenance of balance as well as the support of body weight. Understanding the loading of the third metacarpal bone will help to determine causes of damage to it and ways in which the bone might be conditioned to prevent such damage.
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Peel, J. A., Peel, M. B., & Davies, H. M. S. (2006). The effect of gallop training on hoof angle in thoroughbred racehorses. Equine Vet J Suppl, (36), 431–434.
Abstract: REASONS FOR PERFORMING STUDY: The economic impact of soundness problems in racehorses is very high and low hoof angle at the toe has been associated with a lack of soundness. However, it is not clear what environmental and management factors might contribute to a low hoof angle. OBJECTIVES: To investigate the hypothesis that the hooves of racehorses become flatter when in gallop training, as well as to determine factors contributing to this trend. METHODS: Weekly hoof measurements were taken with a hoof gauge from 45 Thoroughbred racehorses; 4 Thoroughbred show horses kept in consistent conditions and shod by the same farrier as some of the racehorses; and 6 unshod free-ranging horses. A further 15 horses were measured twice in one day to determine the repeatability of the method. RESULTS: Repeatability coefficients were 0.31 degrees for the left hoof and 0.37 degrees for the right. Racehorses in training showed a significant decrease in hoof angle over time while free ranging horses and show horses did not. Free-ranging horses had a significantly lower angle in winter (wet) compared with summer (dry) in both left (P = 0.040) and right (P = 0.017). Show horses had no significant change in hoof angle. Racehorses that had a period of rest during the experiment (n = 11) showed a decrease in hoof angle during training and an increase over their rest period for both hooves (P = 0.005 for the left hoof, P = 0.0009 for the right). CONCLUSIONS: Training for fast exercise in Thoroughbred racehorses is associated with a reduction in hoof angle and wet pasture conditions may also be associated with a reduced hoof angle in free-ranging horses. Potential relevance: Gallop exercise has a potentially large effect on hoof angle and therefore, a change in angle should be expected to occur in racehorses starting fast exercise work. Hence management of horses with abnormally low hoof angles may require an adaptation to their training regime in order to minimise this effect.
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