Glycemic Index of Ten Common Horse Feeds

Two 6 × 6 Latin-square designed experiments examined the glycemic responses to 10 common equine feeds in six Quarter Horse mares. At 8:00 am of the sampling days, horses were offered a meal of 1 of 10 common feeds. The amount of feed offered was calculated on an isocaloric basis at 4 Mcal digestible energy per meal. Jugular blood samples were collected for 300 minutes after feeding, and plasma was analyzed for glucose concentration. The results showed that plasma glucose values peaked approximately 90 to 120 minutes after eating, whereas glycemic index (GI) values ranged from 7 to 129 based on a standard of oats set at a GI of 100. The four feeds with the highest GI values (sweet feed, corn, jockey oats, and oats) were greater (P < .05) than the four feeds with the lowest GI values (beet pulp, alfalfa, rice bran, and soy hulls). Barley and wheat bran had intermediate GI (55–69) values, but were not significantly different from either the high or low group. Whereas large variations in the data were found, conservative utilization of the ranking or categories of GI values of the 10 common horse feeds examined may be useful for formulating rations with different glycemic objectives.