Influence of specific management practices on blood selenium, vitamin E, and beta-carotene concentrations in horses and risk of nutritional deficiency.
Authors: Pitel Mariya O, McKenzie Erica C, Johns Jennifer L, Stuart Robert L
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Selenium and vitamin E deficiencies pose genuine risks of neuromuscular disease in horses, yet this cross-sectional study of 349 equines revealed that despite widespread supplementation practices, over one-third of horses had suboptimal plasma alpha-tocopherol (35.5%) and one-sixth had low or marginal blood selenium concentrations (16.9% combined). Whilst nearly 88% of owners supplemented selenium, those relying solely on salt blocks faced a 20-fold increased risk of deficiency, and only half the supplemented horses received adequate daily vitamin E (≥500 IU/d), with pasture access exceeding 6 hours daily and higher supplemental vitamin E doses both strongly associated with improved alpha-tocopherol status. Beta-carotene concentrations doubled in horses with regular pasture access compared to those without (0.26 versus 0.12 µg/mL), underscoring that grazing cannot be overlooked as a nutritional strategy. For practitioners advising on equine nutrition, these findings suggest that supplement provision alone is insufficient; systematic assessment of actual intake levels, pasture availability, and a move away from mineral salt blocks towards more bioavailable selenium sources warrant serious consideration to reduce the prevalence of these potentially debilitating deficiencies.
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Practical Takeaways
- •Verify selenium supplementation dosing and form with owners—salt block reliance alone is inadequate; aim for consistent daily intake of appropriate supplements in feed
- •Maximize pasture access to at least 6 hours daily when possible, as this significantly improves both vitamin E and beta-carotene status in addition to formal supplementation
- •Target vitamin E supplementation at ≥500 IU/day minimum; over one-third of horses remain deficient or marginal despite owner supplementation efforts, indicating need for dosing review and compliance assessment
Key Findings
- •Despite 88% of horses receiving selenium supplementation, 3.3% had low blood selenium and 13.6% had marginal concentrations; non-supplemented horses were 20 times more likely to have deficiency
- •Suboptimal alpha-tocopherol occurred in 35.5% of horses despite 87.3% receiving supplementation; pasture access >6 hours/day and ≥500 IU/d vitamin E supplementation significantly improved concentrations
- •Horses with >6 hours/day pasture access had 2.2-fold higher plasma beta-carotene concentrations (0.26 vs 0.12 μg/mL) compared to those with limited grazing
- •Reliance on selenium-containing salt blocks was associated with selenium deficiency, suggesting inconsistent intake from voluntary consumption