Hoof Matters: Developing an Athletic Thoroughbred Hoof

SIMPLE SUMMARY: The development of strong, well-conformed hooves begins pre-natally and is on-going throughout the horse’s life. This paper explores specific aspects of the development and adaptation of the distal forelimb in Thoroughbred foals with emphasis on how the hoof responds to weight bearing early in life. The thickness of the epidermal tissues at the toe increased from 2.84 ± 0.41 mm before birth to 4.04 ± 1.10 mm by 4 months of age. The increase in thickness was accompanied by decreased density of horn tubules at the toe while the number and size of horn tubules increased at the medial and lateral quarters. This provides a malleable hoof capsule with increased resistance to fracture toughness at the quarters to allow for skeletal growth. Between 4–6 months of age, the hoof widens, and higher loading on the medial side (>60%) vs. the lateral side (<40%) may be factors that influence mature asymmetric hoof shape. Shortly after 12 months-of-age, the dorsal hoof wall angle becomes parallel with the dorsal wall of the distal phalanx, thus optimizing the functional capacity of the hoof capsule in the weanling Thoroughbred. ABSTRACT: Conformation of the hooves and distal limbs of foals and factors influencing their morphological development have not been reported in detail for the Thoroughbred breed. In this paper we explore morphogenesis of the equine distal limb in Thoroughbred foals with emphasis on adaptations in response to weight bearing early in life that prepare the foal for an athletic career. Novel data from four studies are presented chronologically during key time periods to illustrate specific aspects of distal limb growth and adaptation. Dorsal epidermal thickness increased from 2.84 ± 0.41 mm in utero to 4.04 ± 1.10 mm by 4 months of age. The increase in thickness was accompanied by decreased tubular density, increased inter-tubular material, and an increase in number and size of tubules at the quarters, which provided a malleable hoof capsule to allow for skeletal growth. Between 4–6 months of age, the hoof widens, and higher loading on the medial side (>60%) vs. the lateral side (<40%) may be factors that influence mature asymmetric hoof shape. Shortly after 12 months-of-age, the dorsal hoof wall angle and dorsal parietal angle of the distal phalanx become parallel, thus optimizing the functional capacity of the hoof capsule in the weanling Thoroughbred.