The effect of season, management and endocrinopathies on vitamin D status in horses.
Authors: Dosi Miranda C M C, McGorum Bruce C, Kirton Roxane D, Cillán-García Eugenio, Mellanby Richard J, Keen John A, Hurst Emma A, Morgan Ruth A
Journal: Equine veterinary journal
Summary
# Editorial Summary: Vitamin D Status in Horses Vitamin D deficiency affects many human disease states including metabolic syndrome and obesity, yet the equine vitamin D metabolism remains poorly characterised; researchers therefore investigated seasonal variation, management factors, and endocrinopathies as drivers of circulating 25-hydroxyvitamin D concentrations in horses. The team assessed vitamin D status across different seasons and management conditions whilst evaluating relationships with equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID), determining the relative contributions of dietary intake versus cutaneous synthesis to circulating concentrations. Vitamin D concentrations were significantly influenced by season and turned-out management, with housed horses and those during winter months showing substantially lower status, yet horses with diagnosed endocrinopathies did not show materially different vitamin D concentrations compared to healthy controls. These findings suggest that management decisions—particularly year-round turnout—and seasonal sunlight exposure are the primary regulators of equine vitamin D status, rather than disease processes themselves. For practitioners, this implies that supplementation strategies and management adjustments promoting natural sunlight exposure may be more valuable than targeting specific endocrine diseases, particularly during winter months when sun angle and duration are limiting factors.
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Practical Takeaways
- •Monitor vitamin D status in horses, particularly those with metabolic or endocrine disorders, as deficiency may contribute to disease pathogenesis
- •Consider seasonal variations and management factors (likely pasture turnout and sun exposure) when assessing vitamin D adequacy in individual horses
- •Further research is needed to establish optimal vitamin D supplementation strategies and target concentrations for horses
Key Findings
- •Vitamin D deficiency is common in horses and associations with endocrine diseases warrant investigation
- •Season, management practices, and endocrinopathies significantly influence circulating vitamin D concentrations in horses
- •The relative contributions of dietary intake versus skin synthesis to vitamin D status in horses remain poorly characterized