Heritability of metabolic traits associated with equine metabolic syndrome in Welsh ponies and Morgan horses.
Authors: Norton E M, Schultz N E, Rendahl A K, Mcfarlane D, Geor R J, Mickelson J R, McCue M E
Journal: Equine veterinary journal
Summary
# Equine Metabolic Syndrome: A Heritable Problem Worth Selecting Against Welsh ponies and Morgan horses are particularly predisposed to equine metabolic syndrome (EMS), a multifactorial disorder combining insulin dysregulation, obesity and endocrine dysfunction, yet the relative contribution of genetics versus environment to this condition remains poorly characterised. Researchers used high-density SNP genotyping in 264 Welsh ponies and 286 Morgan horses to estimate heritability (h² SNP) of nine metabolic traits, including fasting insulin, glucose, NEFA, triglycerides, leptin, adiponectin and ACTH, plus glucose and insulin responses to an oral sugar challenge. Remarkably strong heritability estimates emerged in both breeds: basal insulin showed exceptionally high heritability in Welsh ponies (h² = 0.808), whilst adiponectin in Morgans reached 0.913, and six to seven of the nine traits demonstrated moderate-to-high heritability (h² >0.20) in each breed. These findings provide robust genetic evidence for the first time that EMS-associated metabolic traits are substantially heritable, meaning selective breeding decisions could meaningfully reduce disease incidence in predisposed populations. For practitioners advising on breeding, nutrition and management, this work validates the importance of considering metabolic phenotyping as part of selection criteria, particularly given that traits like hyperinsulinaemia and dysregulated adipokine profiles appear substantially under genetic control.
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Practical Takeaways
- •Metabolic traits associated with EMS have substantial genetic components, suggesting selective breeding strategies could reduce disease prevalence in high-risk breeds like Welsh ponies and Morgans
- •Insulin and adiponectin show particularly high heritability, making them potential genetic markers for identifying at-risk animals before clinical signs develop
- •Genetic testing and familial screening may help identify predisposed horses earlier, enabling preventive dietary and management interventions
Key Findings
- •In Welsh ponies, 7 of 9 metabolic traits showed moderate to high heritability (h² >0.20), with insulin showing the highest heritability at 0.808
- •In Morgan horses, 6 of 9 traits were moderately to highly heritable, with adiponectin showing the highest heritability at 0.913
- •Eight of nine EMS-associated metabolic traits demonstrated significant genetic contribution across both breeds
- •ACTH, glucose and triglycerides in Morgans, and GLU-OST in Welsh ponies had insufficient statistical power to determine heritability