Effect of micronization and meal size of corn grain on glycemic response and in vitro hindgut acidosis potential in horses.
Authors: Varasteh Fahimeh, Ebrahimi Seyed Hadi, Naserian Abbas Ali, Zerehdaran Saeid, Heidarian Miri Vahideh
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Micronized Corn and Glycaemic Response in Horses Micronization significantly enhances the digestibility of corn grain in horses, with in vitro studies demonstrating three-fold greater enzymatic disappearance and 38.6% faster hindgut fermentation compared to ground corn; however, these laboratory improvements translate to more modest increases in post-prandial plasma glucose in vivo. In this 2×3 factorial crossover trial involving six mature mares consuming ground versus micronized flaked corn at starch levels of 1–2 g/kg bodyweight per meal, both processing method and increased meal size independently elevated plasma glucose concentrations, with micronized corn producing significantly higher responses (p < 0.001) and the highest starch dose (2 g/kg BW) showing measurably greater glycaemic excursion than 1 g/kg BW (p = 0.005). Whilst micronization's enhanced small intestinal starch availability might theoretically increase hindgut acidosis risk through rapid fermentation of residual starch, the disconnect between in vitro fermentation rates and actual glycaemic outcomes suggests the clinical concern may be overstated, at least within the meal sizes tested. For practitioners, this work underscores that micronized corn grain does improve digestibility and blood glucose response compared to coarser processing, making it a viable option for performance horses or those requiring elevated caloric intake, provided meal size remains moderate (≤1.5 g starch/kg BW) to maintain metabolic stability.
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Practical Takeaways
- •Micronization of corn grain increases starch availability and glucose absorption, which may benefit performance horses but requires careful meal management to avoid metabolic disturbances
- •The discrepancy between rapid in vitro fermentation and moderate in vivo glucose responses suggests micronization may present lower hindgut acidosis risk than expected, making it a safer processing method for whole grain supplementation
- •Meal size matters: feeding larger starch loads (2 g/kg BW) increases glycemic response regardless of processing method; consider dividing grain into smaller frequent meals for metabolically sensitive horses
Key Findings
- •Micronized flaked corn showed three times greater in vitro enzymatic dry matter disappearance compared to ground corn (p < 0.001)
- •Micronized corn residues fermented 38.59% faster than ground corn during in vitro hindgut incubation
- •Horses consuming micronized flaked corn had significantly higher postprandial plasma glucose concentrations (p < 0.001)
- •Increasing starch levels from 1–2 g/kg BW per meal increased plasma glucose concentrations (P = 0.005), but in vivo responses did not match in vitro predictions