Sugars in feeds are analyzed using several methods. The most common is referred to as “total sugar”, and measures simple sugars such as glucose, fructose and sucrose.
In regular hay, the sugar content is about 100 grams per kg, but with a considerable variation. In haylage, part of the original sugar is broken down during fermentation, and the sugar content is usually lower. In grains and concentrates, the sugar content is low (the normal sugar content of oats and barley is only about 18 to 20 grams per kg.). Rations containing added molasses will, however, have a higher content of sugar.
The amount of sugar found in hay and haylage seldom causes problems in horses. The uptake of roughage is spread over many hours of the day. Sugar absorption is therefore taking place over an extended period of time in the small intestine, and does not lead to large fluctuations in blood glucose concentrations.
Horses that have problems with blood sugar regulation or are insulin resistant may still benefit from forage that is low in sugar.
Fructanes are complex molecules (polysaccharides) which grasses store as an energy source. The horse lacks enzymes to digest fructanes in the small intestine, and these carbohydrates will therefore not be digested in the same way as starch and simple sugars. Fructanes are instead transported to the caecum, where they are broken down by microbes. If the ration contains large quantities of fructanes, it can cause, in the same way as too much starch, an imbalance in microbial fermentation and adverse conditions in the caecum. In the case of some horses, this may lead to laminitis. It is therefore important that horses are introduced gradually to a lush, rich pasture.
The level of fructanes in grasses varies with weather conditions and grass species. In cold periods, the fructane content can be higher than in warm periods. On hot sunny summer days, there is little to worry about. In the early summer and autumn, during periods of cold nights and mornings the fructane content of the grass can be very high. It is therefore wise to give extra attention to the horse's reactions to grazing in cool periods, especially early and late in the grazing season.
Since the fructane content of grasses varies so much, specific analyses of fructanes are not commonly used. However, since there are significant differences in the amount of fructanes amongst grass species and varieties, those who grow their own horse feeds also have the option to seed grasses selected for their moderate fructane content.