A term borrowed from human medicine the GI is a number assigned to foods to indicate their ability to raise blood glucose level within two hours of consumption. Glucose is assigned the number 100 and foods with a GI below 55 are considered low GI in humans.
In horses the numbering system has not been adopted but feeds may be described as “low GI’’ to imply that their impact on raising blood glucose level is less than other feeds. High starch feeds like grains have a high GI whereas feeds with more fibre and fat and less starch and sugar content tend to be marketed as ‘low GI’’ to increase their appeal to target groups like stud farms and the owners of horses with insulin resistance.
Because of the difference in food types and digestive systems between humans and horses the GI system is not strictly transferable and should be regarded as a rough guide only.