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The effect of season, management and endocrinopathies on vitamin D status in horses.
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.
Affiliation
  • Dosi MCMC; Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • McGorum BC; Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • Kirton RD; Redwings Horse Sanctuary, Norwich, UK.
  • Cillán-García E; Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • Mellanby RJ; Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • Keen JA; The Roslin Institute, University of Edinburgh Roslin, Midlothian, UK.
  • Hurst EA; Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • Morgan RA; The Roslin Institute, University of Edinburgh Roslin, Midlothian, UK.
Equine Vet J ; 55(4): 672-680, 2023 Jul.
Article in En | MEDLINE | ID: mdl-36054781
BACKGROUND: Vitamin D deficiency is common in humans and is increasingly linked to the pathogenesis of a multitude of diseases including obesity and metabolic syndrome. The biology of vitamin D in horses is poorly described; the relative contribution of the diet and skin synthesis to circulating concentrations is unclear and associations with the endocrine disease have not been explored. OBJECTIVES: To determine the relationship between management, season and endocrine disease and vitamin D status in horses. STUDY DESIGN: Cross-sectional cohort study. METHODS: Plasma concentrations of 25-hydroxyvitamin D2 (25(OH)D2 ) and D3 (25(OH)D3 ) were measured by liquid chromatography-tandem mass spectrometry in 34 healthy unsupplemented grazing ponies and 22 stabled Thoroughbreds receiving supplementary vitamin D3 in feed. A nested group of 18 grazing ponies were sampled on long and short days (>12 and <12 h of light/day) to determine the effect of sunlight exposure. In addition, the relationships between age, sex, adiposity, serum insulin, adrenocorticotropic hormone and vitamin D status were assessed in a mixed group of 107 horses using a linear regression model. RESULTS: All animals had a measurable level of 25(OH)D2 (median 10.7 nmol/L) whilst 25(OH)D3 was only detected in Thoroughbreds receiving D3 supplementation. Thoroughbreds had lower concentrations of 25(OH)D2 than ponies (7.4 vs. 12.6 nmol/L, p < 0.01). In grazing ponies, 25(OH)D2 concentrations were significantly higher on long days compared to short days (14.4 vs. 8.7 nmol/L, p < 0.01), whilst 25(OH)D3 was undetectable. Measures of increased adiposity, but not basal insulin, were associated with higher 25(OH)D2 concentrations, conversely to humans. Increasing ACTH was associated with lower 25(OH)D2 (p < 0.01). MAIN LIMITATIONS: Vitamin D2 concentrations were not measured in grass or forage. CONCLUSIONS: In horses 25(OH)D2 is the predominant vitamin D metabolite, and there is an apparent lack of endogenous vitamin D3 production. The relationship between vitamin D and endocrine disorders in horses does not reflect that of other species and warrants further investigation.
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Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Endocrine System Diseases / Insulins / Horse Diseases Type of study: Observational_studies / Risk_factors_studies Limits: Animals / Humans Language: En Journal: Equine Vet J Year: 2023 Document type: Article Country of publication: United States

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Endocrine System Diseases / Insulins / Horse Diseases Type of study: Observational_studies / Risk_factors_studies Limits: Animals / Humans Language: En Journal: Equine Vet J Year: 2023 Document type: Article Country of publication: United States