Factors Affecting Glycaemic Index of Feds for Horses

Introduction The glycaemic response to foods has been of concern in humans for many years, especially in the management of obesity, diabetes mellitus and cardiovascular diseases. The glycaemic index (GI) is a ranking of starchy foods based on the postprandial blood glucose response compared with the response to a 50-g glucose test load (Jenkins et al. 1981). The GI was originally introduced to classify different sources of carbohydrate-rich foods, usually those with an energy content of > 80% from the available carbohydrates, as to their effect on post-meal glycaemia. By definition, the GI compares equal quantities of carbohydrate and provides a measure of carbohydrate quality but not quantity. Thus, low-GI carbohydrates were classified as those that are digested and absorbed slowly and lead to a low glycaemic response, while high-GI carbohydrates are digested and absorbed rapidly and lead to a high glycaemic response (Foster-Powell and Brand Miller 1995). In 1997 the concept of glycaemic load (GL) was introduced to quantify the overall glycaemic effect of a meal as both, the quality and quantity of carbohydrate determines an individual ́s glycaemic response to a meal (Foster-Powell et al. 2002). As defined, the GL is the product of a food ́s GI and its total available carbohydrate content (GL = [GI x carbohydrate (g)] / 100). There are convenient international tables of glycaemic indexes and loads for more than 700 foods containing all published data on the GIs of individual foods (Foster-Powell and Brand Miller 1995, Foster-Powell et al. 2002). There is interest in the glycaemic response in horses for conditions such as exercise performance, obesity, insulin resistance, laminitis and osteochondrosis (Kronfeld et al. 2005). There is information available on the influence of different grain sources on glucose and insulin responses in the horse, but little is known about the influence of different grain processing techniques and the effect of mixed meals (compound feeds or grain-roughage mixtures) on glucose and insulin control. Furthermore, no standardised glycaemic or insulinaemic index has yet been formulated for horses such as that for humans.