How Do Different Diets Affect Glycemic Response in Horses?

The purpose of this experiment was to determine glycemic response in horses fed six different feeds (sweet feed, whole oats, cracked corn, high fiber mix, sweet feed plus oil, alfalfa forage) at three different levels of intake (1.65, 3.31, or 5.51 lb).

Area under the curve indicated differences in glycemic response between low (1.65 lb) and high (5.51 lb) intake levels of all diets combined. Sweet feed and whole oats demonstrated the greatest glycemic response, while alfalfa and sweet feed plus corn oil provided the lowest response. Plotting the glycemic index by feed and level of intake revealed an appreciable drop in the index for whole oats fed at 5.51 lb compared to that at 1.65 lb and relative to glycemic indexes generated for other feeds. Mean glucose was highest for sweet feed, whole oats, and the low starch/high fiber mix and lowest for the alfalfa diet. Peak glucose was similar for all diets except alfalfa forage. Time to peak glucose was greatly increased in the sweet feed plus corn oil diet, while the remaining diets demonstrated similar responses. Increasing level of intake from 1.65 lb to 3.31 lb per feeding increased time to peak glucose by 45 ± 14.1 minutes.

Results of this study indicate that different grain diets demonstrate different glycemic responses and adding fat reduces both the area under the curve and peak glucose values, as measured within this experimental design. More research is required to determine the relevance of glycemic response in predicting the effects of different feed ingredients on a horse’s performance or behavior.

This report of KER’s 1999 research was published in Proceedings of the 16th Equine Nutrition and Physiology Society Symposium.

Read the entire research paper, titled Feed Type and Intake Affect Glycemic Response in Thoroughbred Horses.