Effect of long-term overfeeding of a high-energy diet on glucose tolerance in Shetland pony mares.
Authors: d' Fonseca Nicky M M, Gibson Charlotte M E, van Doorn David A, de Ruijter-Villani Marta, Stout Tom A E, Roelfsema Ellen
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Chronic overfeeding is recognised as a pathway to equine metabolic syndrome, yet the temporal relationship between excessive energy intake, insulin dysregulation, and obesity remains poorly characterised. Researchers fed Shetland pony mares 200% of their net energy requirements for 24 weeks, followed by a hay-only recovery period of 17 weeks and a second overfeeding phase of 29 weeks, whilst performing oral glucose tolerance tests throughout; control animals received 100% net energy requirements across all phases. Body weight in the overfed group increased markedly by approximately 27% during each high-energy feeding period, accompanied by a paradoxical initial improvement in glucose clearance (decreased area under the curve for plasma glucose) within just five weeks—yet this was rapidly superseded by significant hyperinsulinaemia, indicating insulin dysregulation despite enhanced glucose metabolism. Notably, the hyperinsulinaemic status reversed completely during the hay-only feeding period regardless of whether body condition had normalised, but reappeared quickly upon dietary reintroduction, suggesting that insulin resistance in ponies may be reversible through dietary restriction alone. For practitioners, these findings underscore that even brief periods of overfeeding can trigger insulin dysregulation within weeks, that metabolic improvements follow dietary correction faster than weight loss alone would suggest, and critically, that ponies with a history of overfeeding remain metabolically vulnerable to rapid relapse, warranting sustained dietary vigilance in predisposed individuals.
Read the full abstract on PubMed
Practical Takeaways
- •Overfeeding energy to ponies rapidly causes insulin dysregulation and obesity within weeks; restrict concentrate intake and ensure diet matches maintenance requirements
- •Insulin dysfunction can develop in healthy, non-obese animals on high-energy diets—metabolic health requires dietary control independent of current body condition
- •While insulin abnormalities improve with hay-only feeding, susceptibility to rapid relapse means long-term dietary management is essential for metabolically predisposed animals
Key Findings
- •High-energy diet (200% NE requirements) caused 27% body weight increase per feeding period in Shetland pony mares
- •Plasma glucose AUC decreased within 5 weeks of high-energy feeding while insulin AUC increased significantly, indicating hyperinsulinemia despite improved glucose metabolism
- •Basal plasma glucose and peak insulin concentrations were significantly higher in high-energy group compared to controls
- •Hyperinsulinemic status reversed after 17 weeks of hay-only feeding but rapidly returned upon resuming high-energy diet regardless of body condition