Effect of age and dietary carbohydrate profiles on glucose and insulin dynamics in horses.
Authors: Jacob S I, Geor R J, Weber P S D, Harris P A, McCue M E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Age and Dietary Carbohydrate Effects on Equine Glucose-Insulin Dynamics Aged horses demonstrate heightened acute insulin responses to intravenous glucose challenge compared with adults (582 vs 358 mIU/mL, P=0.03), suggesting age-related changes in pancreatic beta cell function that warrant consideration during metabolic assessment. Jacob and colleagues fed 16 healthy Thoroughbreds and Standardbreds (eight aged 20.6 years, eight aged 8.8 years) four isocaloric diets varying in carbohydrate composition—control, high-starch, high-fibre, and high-sugar—then evaluated insulin sensitivity, glucose effectiveness and postprandial responses using insulin-modified glucose tolerance tests and oral sugar challenges. Surprisingly, insulin sensitivity improved significantly when horses consumed starch or sugar-rich diets compared with the control (adult SI increased from 2.0 to 3.3–3.4; aged from 1.4 to 2.8–4.0), though both age groups developed marked postprandial hyperinsulinaemia after starch and sugar meals, with aged horses showing particularly elevated insulin area-under-curve values (35,205 vs 21,581 mIU·min/mL in adults on starch). For practitioners, these findings emphasise that standard glucose tolerance reference ranges may not apply across different age groups, and that even healthy horses without insulin resistance can mount exaggerated insulin responses to concentrated carbohydrates—information critical for managing metabolic health and preventing laminitis risk in both adult and geriatric populations.
Read the full abstract on PubMed
Practical Takeaways
- •Aged horses (>20 years) have different insulin responses than younger adults; dietary management strategies should be tailored by age group rather than applying one approach to all mature horses
- •High-starch and high-sugar meals cause significant insulin spikes in both young and aged horses; consider fiber-based alternatives when managing insulin sensitivity or metabolic concerns
- •Monitor postprandial glucose and insulin responses when changing diet composition, as improvements in insulin sensitivity don't necessarily translate to reduced hyperinsulinaemic responses to specific meal types
Key Findings
- •Aged horses (20.6 years) showed significantly higher acute insulin response to glucose (AIRg 582.0) compared to adult horses (8.8 years, AIRg 358.0; P=0.03)
- •Both adult and aged horses demonstrated improved insulin sensitivity (SI) when fed starch and sugar diets compared to control diet (P≤0.029)
- •Starch and sugar meals induced postprandial hyperinsulinaemia in both age groups, with aged horses on starch diet showing higher AUCi (35205.0) than adults (21581.0)
- •Age and dietary carbohydrate profile are independent factors affecting glucose-insulin dynamics and should both be considered in nutritional management