Thoroughbred Racehorses in Hong Kong Require Vitamin D Supplementation to Mitigate the Risk of Low Vitamin D Status.
Authors: Dosi Miranda C M, Riggs Chris M, May Jessica, Lee Adele, Cillan-Garcia Eugenio, Pagan Joe, McGorum Bruce C
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Vitamin D Status in Hong Kong Racehorses Vitamin D deficiency remains largely uncharacterised in equine athletes, yet management practices in certain regions may substantially increase this risk. Miranda and colleagues measured circulating 25-hydroxyvitamin D metabolites in 79 non-grazing Hong Kong racehorses and compared them with published data from 22 UK grazing racehorses, finding that Hong Kong horses had significantly depressed total 25-hydroxyvitamin D and D2 concentrations, with D2 undetectable in 19% of animals. Longitudinal sampling of 41 Hong Kong horses revealed a progressive decline in D2 status with duration in the region, whilst D3 supplementation emerged as the critical determinant of adequate vitamin D status—a finding that mirrors previously documented inverse relationships between D2 and D3 metabolism in humans. For practitioners managing racehorses in sunny climates with limited pasture turnout and grazing opportunity, these results underscore the necessity of deliberate vitamin D3 supplementation rather than relying on sunlight exposure or forage intake alone; however, further investigation into optimal supplementation protocols, forms, and target serum concentrations in performance horses remains essential for evidence-based recommendations.
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Practical Takeaways
- •Non-grazing racehorses in Hong Kong require vitamin D3 supplementation to prevent deficiency; standard unsupplemented management is insufficient
- •Duration of time in Hong Kong directly impacts vitamin D status; consider baseline testing and supplementation protocols for imported or relocated horses
- •Vitamin D supplementation strategy should focus on D3 form, as D2 sources appear ineffective in non-grazing environments
Key Findings
- •Hong Kong racehorses had significantly lower serum total 25OHD and 25OHD2 concentrations compared to UK grazing racehorses
- •25OHD2 was undetectable in 15/79 HK horses and declined with duration of stay in HK
- •HK racehorses depend on D3 supplementation to maintain adequate vitamin D status
- •An inverse relationship between 25OHD2 and 25OHD3 serum concentrations was observed in horses for the first time