The effects of diet on blood glucose, insulin, gastrin and the serum tryptophan: large neutral amino acid ratio in foals.
Authors: Wilson A Douglas, Badnell-Waters Amanda J, Bice Rachel, Kelland Ailison, Harris Pat A, Nicol Christine J
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Diet, Metabolism and Neurobiology in Growing Foals High-starch and high-sugar diets are known to influence both the physical and behavioural health of foals, yet the underlying physiological mechanisms remain incompletely characterised. Douglas and colleagues investigated these metabolic pathways by comparing two dietary approaches—a starch and sugar-rich concentrate versus a fat and fibre-rich alternative—fed to two groups of eight foals from 4 to 42 weeks of age alongside ad libitum forage. The starch and sugar group demonstrated significantly elevated total blood glucose and notably lower gastrin concentrations during the 6-hour post-feeding period at 40 weeks of age, though insulin responses did not differ meaningfully between groups; additionally, the tryptophan to large neutral amino acid ratio showed a trend towards diet-dependent variation over time, suggesting potential effects on serotonin synthesis and neurological function. Gastric health remained sound in both groups at endoscopic examination, indicating that diet composition did not compromise mucosal integrity under these conditions. These findings hint at mechanistic pathways—particularly relating to glucose metabolism and the neurotransmitter-regulating amino acid profile—through which concentrate composition might influence foal physiology and potentially behaviour, warranting further investigation into whether the metabolic profiles observed correlate with observable temperament or stress responses during this critical developmental window.
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Practical Takeaways
- •High carbohydrate diets produce marked differences in glucose metabolism and gastrin secretion in young foals; consider fat and fibre-based diets if managing metabolic or behavioural issues
- •Despite short-term physiological differences, both diet types maintained healthy gastric mucosa, suggesting neither diet caused acute gastric damage in this study period
- •The tryptophan:LNAA ratio trend suggests diet composition may influence serotonin precursor availability, which could have behavioural implications for foals—further investigation recommended before dietary recommendations
Key Findings
- •At 40 weeks of age, foals fed starch and sugar diets had significantly higher blood glucose and lower gastrin levels than foals fed fat and fibre diets during the 6-hour post-feeding period
- •Insulin levels did not differ significantly between diet groups despite differences in glucose and gastrin responses
- •Gastric mucosa remained healthy in both diet groups at 25 and 42 weeks of age with no significant differences in faecal pH
- •Serum tryptophan to large neutral amino acid ratio showed a trend towards diet-time interaction, suggesting potential effects on neurotransmitter precursor availability