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Equine veterinary journal2022; 55(4); 672-680; doi: 10.1111/evj.13873

The effect of season, management and endocrinopathies on vitamin D status in horses.

Abstract: 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. Objective: To determine the relationship between management, season and endocrine disease and vitamin D status in horses. Methods: 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). Conclusions: 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. Unassigned: Vitamin-D-Mangel ist beim Menschen weit verbreitet und wird zunehmend mit der Entstehung einer Vielzahl von Krankheiten in Verbindung gebracht, darunter Fettleibigkeit und das metabolische Syndrom. Die Biologie von Vitamin D bei Pferden ist nur unzureichend beschrieben; der relative Beitrag der Ernährung und der Hautsynthese zu den zirkulierenden Konzentrationen ist unklar, und Zusammenhänge mit endokrinen Erkrankungen sind nicht untersucht worden. Unassigned: Ermittlung des Zusammenhangs zwischen Management, Jahreszeit und endokriner Erkrankung mit dem Vitamin-D-Status bei Pferden. Methods: Querschnittskohortenstudie. Methods: Die Plasmakonzentrationen von 25-Hydroxyvitamin D2 (25(OH)D2 ) und D3 (25(OH)D3 ) wurden mittels LC-MS/MS bei 34 gesunden, nicht mit Vitamin D3 gefütterten, grasenden Ponys und 22 Vollblütern im Stall, die zusätzlich Vitamin D3 im Futter erhielten, gemessen. Eine verschachtelte Gruppe von 18 weidenden Ponys wurde an langen und kurzen Tagen (>12 und <12 Stunden Licht/Tag) beprobt, um die Auswirkungen der Sonnenlichtexposition zu bestimmen. Darüber hinaus wurden die Beziehungen zwischen Alter, Geschlecht, Adipositas, Seruminsulin, adrenocorticotropem Hormon und Vitamin-D-Status in einer gemischten Gruppe von 107 Pferden mit Hilfe eines linearen Regressionsmodells bewertet. Unassigned: Alle Tiere wiesen messbare 25(OH)D2 -Spiegel auf (Median 10.7 nmol/L), während 25(OH)D3 nur bei Vollblütern nachgewiesen wurde, die eine D3-Supplementierung erhielten. Vollblüter wiesen niedrigere Konzentrationen von 25(OH)D2 auf als Ponys (7.4 nmol/L vs. 12.6 nmol/L p < 0.01). Bei grasenden Ponys waren die 25(OH)D2 -Konzentrationen an langen Tagen signifikant höher als an kurzen Tagen (14.4 nmol/L vs. 8.7 nmol/L, p < 0.01), während 25(OH)D3 nicht nachweisbar war. Messungen der erhöhten Adipositas, aber nicht des Grundinsulins, wurden mit höheren 25(OH)D2 -Konzentrationen in Verbindung gebracht, im Gegensatz zum Menschen. Steigendes ACTH war mit einem niedrigeren 25(OH)D2 -Wert verbunden (p < 0.01). Unassigned: Die Vitamin-D2 -Konzentration im Gras oder Futter wurde nicht gemessen. Unassigned: Bei Pferden ist 25(OH)D2 der vorherrschende Vitamin-D-Metabolit, und es gibt offensichtlich einen Mangel an endogener Vitamin-D3 -Produktion. Der Zusammenhang zwischen Vitamin D und endokrinen Störungen bei Pferden spiegelt nicht die Verhältnisse bei anderen Tierarten wider und bedarf weiterer Untersuchungen.
© 2022 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2022-09-02 PubMed ID: 36054781DOI: 10.1111/evj.13873Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research aimed to understand the relationship between season, management, endocrine disease and vitamin D status in horses. The findings indicate that vitamin D levels in horses are predominantly derived from 25(OH)D metabolite and seemed to lack endogenous production. Its relationship with endocrine disorders in horses differs from other species, demanding further investigations.

Methodology

  • The article describes a cross-sectional cohort study carried out on a sample of horses to measure distinct vitamin D metabolites.
  • Plasma concentrations of 25-hydroxyvitamin D (25(OH)D) were measured in 34 healthy unsupplemented grazing ponies and in 22 stabled Thoroughbreds receiving supplementary vitamin D in their feed.
  • Another smaller cohort of 18 grazing ponies was studied during different daylight durations to evaluate the impact of sunlight exposure on vitamin D levels.
  • The researchers assessed relationships between factors such as age, sex, adiposity, serum insulin, adrenocorticotropic hormone (ACTH), and vitamin D status in a mixed group of 107 horses using a linear regression model.

Results

  • All animals in the study showed measurable levels of 25(OH)D, while 25(OH)D was only found in Thoroughbreds receiving vitamin D supplements.
  • Thoroughbreds had lower 25(OH)D concentrations than ponies.
  • Grazing ponies exhibited significantly higher 25(OH)D concentrations on long days compared to short days.
  • Increased adiposity was found to be associated with higher 25(OH)D concentrations, contrary to human findings.
  • Higher ACTH levels were associated with lower 25(OH)D levels.

Conclusions

  • The study did not measure the concentration of vitamin D in the grass or forage that the horses consumed – a factor that may have otherwise contributed to assessing the overall vitamin D intake of the horses.
  • The results show that 25(OH)D is the dominant vitamin D metabolite in horses. However, there appears to be an overall lack of endogenous vitamin D production in the animals.
  • Based on the findings, the correlation between vitamin D and endocrine disorders in horses is noted to be dissimilar from other species.
  • The researchers suggest that this area requires further investigation to better understand the peculiarities in the vitamin D-endocrine relationship in horses.

Cite This Article

APA
Dosi MCMC, McGorum BC, Kirton RD, Cillán-García E, Mellanby RJ, Keen JA, Hurst EA, Morgan RA. (2022). The effect of season, management and endocrinopathies on vitamin D status in horses. Equine Vet J, 55(4), 672-680. https://doi.org/10.1111/evj.13873

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 55
Issue: 4
Pages: 672-680

Researcher Affiliations

Dosi, Miranda C M C
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
McGorum, Bruce C
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
Kirton, Roxane D
  • Redwings Horse Sanctuary, Norwich, UK.
Cillán-García, Eugenio
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
Mellanby, Richard J
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • The Roslin Institute, University of Edinburgh Roslin, Midlothian, UK.
Keen, John A
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
Hurst, Emma A
  • The Roslin Institute, University of Edinburgh Roslin, Midlothian, UK.
  • Mass Spectrometry Core, Edinburgh Clinical Research Facility, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
Morgan, Ruth A
  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • Queen's Medical Research Institute, The University of Edinburgh, Edinburgh, UK.
  • Scotland's Rural College, Edinburgh, UK.

MeSH Terms

  • Humans
  • Horses
  • Animals
  • Seasons
  • Cross-Sectional Studies
  • Vitamin D
  • Cholecalciferol
  • Endocrine System Diseases / veterinary
  • Insulins
  • Horse Diseases

Grant Funding

  • Fiona and Ian Russell Seed Corn Grant

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Citations

This article has been cited 4 times.
  1. Alemi M, Ahmadi Sheikhsarmast S, Mohri M. Serum 25(OH) Vitamin D Concentrations in Horses: Effects of Age, Gender, Breed, Skin Colour and Season. Vet Med Sci 2025 Jan;11(1):e70092.
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  2. Bruins-van Sonsbeek LGR, Corbee RJ. Serum 25(OH)D Analysis in Captive Pachyderms (Loxodonta africana, Elephas maximus, Diceros bicornis, Rhinoceros unicornis, Tapirus indicus) in Europe. Animals (Basel) 2024 Oct 2;14(19).
    doi: 10.3390/ani14192843pubmed: 39409792google scholar: lookup
  3. Mendoza FJ, Toribio RE, Perez-Ecija A. Metabolic and Endocrine Insights in Donkeys. Animals (Basel) 2024 Feb 10;14(4).
    doi: 10.3390/ani14040590pubmed: 38396558google scholar: lookup
  4. Dosi MCM, Riggs CM, May J, Lee A, Cillan-Garcia E, Pagan J, McGorum BC. Thoroughbred Racehorses in Hong Kong Require Vitamin D Supplementation to Mitigate the Risk of Low Vitamin D Status. Animals (Basel) 2023 Jun 29;13(13).
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