Deconditioning reduces mineral content of the third metacarpal bone in horses.

This research investigates how detraining or “deconditioning” affects the density and calcium status of a horse’s metacarpal bone, concluding that lack of exercise led to notable decrease in bone density irrespective of the dietary calcium concentration.

Study Overview

• This research involved eleven well-conditioned Arabian horses taken out of regular training and confined within stalls for twelve weeks.
• Despite the confinement, horses were walked on a mechanical walker for two thirty-minute sessions, seven days a week.
• Two types of diets were provided to the horses: one containing normal Calcium concentration (.36% Ca, referred as CC) and the other with high Calcium concentration (.62% Ca, referred as HC).
• Data, including bone mineral content (BMC) along with other blood and serum samples, were collected every twenty-one days to monitor the effects of deconditioning and dietary calcium on bone density.

Methodology

• The BMC of the horse’s third metacarpal bone was estimated by using radiographic photometry. An aluminum step wedge was used as a reference standard for image analysis in each radiograph.
• Also, blood samples were analyzed for various mineral levels including total and ionized Calcium, parathyroid hormone, osteocalcin, hydroxyproline, electrolytes, and blood gases.

Results and Conclusion

• The results of the study showed that during deconditioning, the bone mineral content decreased by approximately 1.1g/2cm, or by .45% every week.
• This decrease was consistent irrespective of the dietary calcium concentration in their diet, showing that high dietary calcium levels did not prevent the loss of bone density.
• Serum Calcium concentration was found to increase with deconditioning.
• The study concluded that loss of bone mineral content due to the limitation of physical exertion over twelve weeks can potentially weaken bones, which may in turn raise the odds of skeletal injuries when the horses resume training.
• Interestingly, an elevated dietary calcium intake—up to twice the recommended level—couldn’t offset the deconditioning-induced drop in bone mineral content.