Enteroinsular axis response to carbohydrates and fasting in healthy newborn foals
Authors: Rings Lindsey M., Swink Jacob M., Dunbar Laura K., Burns Teresa A., Toribio Ramiro E.
Journal: Journal of Veterinary Internal Medicine
Summary
# Enteroinsular Axis Response in Neonatal Foals The enteroinsular axis—the coordinated release of gut hormones (GIP and GLP-1) that stimulate insulin secretion following oral nutrient intake—remains poorly characterised in newborn foals despite its potential relevance to both healthy neonatal metabolism and disease management in compromised individuals. Rings and colleagues conducted a prospective investigation of 36 healthy Standardbred foals ≤4 days old, administering oral and intravenous glucose challenges at three dose levels (300, 500, 1000 mg/kg), an oral lactose test, and fasting periods whilst measuring plasma glucose, insulin, GIP, and GLP-1 responses over 210 minutes. Remarkably, only oral lactose provoked a significant rise in blood glucose; by contrast, all intravenous glucose doses caused hyperglycemia and hyperinsulinemia, yet incretin hormone concentrations (GIP and GLP-1) actually decreased during fasting and glucose challenges—until foals nursed, whereupon rapid simultaneous increases in all four parameters occurred. These findings indicate that healthy neonatal foals possess a functional enteroinsular axis substantially more responsive to milk and lactose than to glucose alone, suggesting non-carbohydrate milk constituents drive incretin secretion, and that foals tolerate 4-hour fasts without hypoglycaemia. For practitioners, this work implies that frequent milk access maintains appropriate gut hormone signalling and metabolic homeostasis in neonates, potentially informing supportive care strategies in sick foals where enteroinsular dysregulation is common.
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Practical Takeaways
- •Newborn foals require frequent access to mare's milk (not just glucose supplementation) to maintain proper metabolic hormone function and intestinal health
- •Short periods of fasting (up to 4 hours) are physiologically safe in healthy neonates, but prolonged fasting may impair the enteroinsular axis
- •Non-carbohydrate factors in mare's milk are critical for normal metabolic development—recognize that IV glucose alone does not replicate the metabolic response to nursing
Key Findings
- •Healthy newborn foals have a functional enteroinsular axis more responsive to milk and lactose than glucose alone
- •All IV glucose doses induced hyperglycemia and hyperinsulinemia, whereas only PO lactose caused significant blood glucose increases
- •GIP and GLP-1 concentrations decreased during fasting but increased rapidly when foals nursed
- •Foals can be safely fasted for 4 hours without developing hypoglycemia