Effects of corn processing on the glycaemic and insulinaemic responses in horses

This study was conducted to evaluate the effects of different corn processing techniques on the glycaemic and insulinaemic responses in horses. It was hypothesized that the changes in pre-caecal starch digestibility caused by various types of corn processing would alter the post-prandial glycaemic and/or insulinaemic response. Six horses were fed in random order: untreated, finely ground, steamed, micronized, steam-flaked and popped corn. The total corn intake was adjusted to 630 g starch/horse/day (1.2-1.5 g starch/kg BW/day). During a stabilization period of 10 days, horses also received 6 kg grass hay/horse/day. At blood collection day horses were fed their test diet (exclusively corn), and blood samples were taken at defined times. Corn feeding resulted in a significant increase in mean plasma glucose and insulin concentration, but glucose and insulin peaks as well as areas under the curve (AUC) were not clearly influenced by corn processing. The glycaemic index (in which each test diet's plasma glucose AUC was expressed relative to untreated corn) varied between 91.4 +/- 9.4% (steamed corn) and 108.4 +/- 11.8% (popped corn, treatment n.s.), the insulinaemic index (in which each test diet's plasma insulin AUC was expressed relative to untreated corn) ranged between 98.2 +/- 12.6% (steamed corn) and 121.0 +/- 29.9% (micronized corn, treatment n.s.). However, the well-established improvement in pre-caecal starch digestibility was not reflected by differences in the glucose or insulin responses.