A Review of Three Decades of Research Dedicated to Making Equine Bones Stronger: Implications for Horses and Humans

SIMPLE SUMMARY: Skeletal injuries are common in athletic horses. This literature review covers over three decades of research focused on preventing bone-related injuries and demonstrates how research develops over time. In an initial study evaluating the role dietary silicon can play in racehorse injuries, an observation of mineral loss from the cannon bone was observed after the commencement of training. Subsequent work revealed the loss was associated with horses being removed from pasture and placed into stalls, resulting in decreased mechanical loading on the skeleton. As bone responds to the load placed upon it, continued research focused on housing and exercise requirements to prevent such bone loss. Only short sprints are needed to maintain or increase bone strength. Conversely, endurance exercise, without high-speed exercise, fails to cause bone to become stronger. Exercise can be either forced or voluntary but having free access to exercise does not guarantee that animals will perform it. Thus, horse behavior needs to be taken into consideration. While proper nutrition is critical for bone health, it does not guarantee it without appropriate exercise. Pharmaceuticals impact various factors associated with bone health. Many items influencing equine bone health can also be applied to humans. ABSTRACT: Much research has been conducted in an attempt to decrease skeletal injuries in athletic horses. The objective of this literature review is to compile the findings of over three decades of research in this area, make practical recommendations, and describe how research can develop over the years. An initial study investigating the role of bioavailable silicon in the diets of horses in race training produced the unexpected finding of decreased bone mineral content of the third metacarpus subsequent to the onset of training. Further studies revealed this decrease to be associated with stall housing eliminating high-speed exercise, leading to disuse osteopenia. Only relatively short sprints (between 50 and 82 m) were necessary to maintain bone strength and as few as one sprint per week provided the needed stimuli. Endurance exercise without speed fails to elicit the same benefits to bone. Proper nutrition is also required for optimal bone health, but without the right exercise, strong bone cannot be maintained. Several pharmaceuticals may have unintended consequences capable of impairing bone health. Many of the factors influencing bone health in horses also exist in humans including a sedentary lifestyle, improper nutrition, and pharmaceutical side-effects.