Effects of age and diet on glucose and insulin dynamics in the horse.
Authors: Rapson J L, Schott H C, Nielsen B D, McCutcheon L J, Harris P A, Geor R J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Effects of age and diet on glucose and insulin dynamics in the horse Rapson et al. (2018) investigated how age and dietary composition influence insulin sensitivity and glucose metabolism in horses, addressing a gap in equine nutritional science where these relationships have been poorly characterised. Eight adult mares (5–12 years) and nine aged mares (>19 years) were fed three different diets for 6-week periods—forage only, forage with starch/sugar-rich concentrate, or forage with oil/fibre-rich concentrate—with insulin sensitivity assessed via intravenous glucose tolerance testing and glucose/insulin responses measured following a standardised meal challenge. Aged mares demonstrated consistently elevated acute insulin responses to glucose and reduced insulin sensitivity compared with adults regardless of diet, whilst both groups showed improved insulin dynamics when fed starch/sugar-rich concentrate relative to forage-only diets, though this effect was more pronounced in the older horses. These findings have significant implications for nutrition management: aged horses appear to require particular attention to dietary carbohydrate composition, as their heightened insulin responses to both intravenous and oral carbohydrate challenges may predispose them to metabolic disorders; practitioners should therefore consider feeding oil/fibre-rich concentrates or maintaining strict forage-based diets in older horses, particularly those with signs of insulin dysregulation, while recognising that carbohydrate restriction alone may not fully compensate for age-related changes in glucose metabolism.
Read the full abstract on PubMed
Practical Takeaways
- •Aged horses (>19 years) require closer monitoring of insulin and glucose responses; feed management may help improve insulin sensitivity in older animals
- •Starch/sugar-rich concentrate supplementation may paradoxically improve insulin sensitivity in aged horses compared to forage-only diets, contrary to common assumptions
- •Consider age-specific metabolic assessment when managing glucose tolerance and metabolic health in mature and senior horses
Key Findings
- •Aged horses (>19 years) showed greater acute insulin response to glucose (AIRg) and lower insulin sensitivity (SI) compared to adult horses (5-12 years), regardless of diet
- •Both AIRg and SI improved in aged mares after starch/sugar-rich diet adaptation compared to hay-only diet
- •Peak insulin concentration and area under insulin curve during standardized meal challenge were significantly greater in aged versus adult mares across all diets
- •Insulin responses to both intravenous and oral nonstructural carbohydrate challenge increase with age in healthy horses