Effect of Weight Change on Markers of Bone Turnover and Phosphorus Excretion.
Authors: Fowler Ashley L, Pyles M B, Hayes S H, Crum A D, Harris P A, Krotky A, Lawrence L M
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Weight Change Effects on Equine Bone Metabolism Maintaining appropriate body condition in horses involves more than aesthetic considerations—evidence now suggests that the rate and direction of weight change directly influence bone turnover and mineral metabolism. Fowler and colleagues investigated this relationship by assigning 15 mature horses to three dietary treatments over approximately four weeks: caloric restriction (−1.16 kg/day weight loss), maintenance feeding (minimal weight change), and overfeeding (0.49 kg/day gain), whilst keeping protein and mineral content consistent across all groups. The weight-loss group demonstrated significantly elevated bone resorption markers (specifically C-terminal telopeptides of type-I collagen), a negative correlation between weight loss and resorption activity, and a tendency toward increased faecal phosphorus excretion compared to weight-gaining horses—suggesting that rapid weight loss mobilises bone mineral reserves. These findings carry practical implications for managing horses during conditioning programmes, rehabilitation periods, or seasonal weight fluctuations; aggressive caloric restriction may compromise skeletal integrity through accelerated bone turnover, potentially affecting performance horses and those recovering from injury. Further investigation into the timeline of these metabolic changes and longer-term consequences would help practitioners establish safer protocols for intentional weight management.
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Practical Takeaways
- •Rapid weight loss in horses may accelerate bone resorption and increase mineral losses; consider implications for horses undergoing planned weight reduction programs
- •Weight maintenance appears to optimize bone metabolism compared to extremes of gain or loss; horses requiring dietary changes should be monitored for bone health markers
- •Nutritional strategies that maintain stable body weight may better support skeletal integrity than programs involving rapid weight fluctuations
Key Findings
- •Weight loss of -1.16 kg/d increased bone resorption (CTX-I correlation r = -0.62, P = .014) compared to weight gain of 0.49 kg/d
- •Weight change tended to positively correlate with bone alkaline phosphatase (bone formation marker) at r = 0.48, P = .068
- •Fecal phosphorus output tended to be lower in weight-gaining horses than weight-losing horses (P = .085), suggesting increased mineral loss during weight loss
- •Weight change in horses influences both bone metabolism and mineral excretion over a 27-day period