Why is forage so important? Forage is important because of the design and function of a horse’s digestive system (see page 19 for diagram). Horses are classified as post gastric fermentors or non-ruminant herbivores and their digestive systems differ greatly from that of a cow. The horse’s digestive tract is much smaller and consequently, it cannot eat as much forage as a cow. A horse is only able to break down about 30% of the cellulose in feed. The hindgut is the main site of microbial activity in the horse as compared to the rumen in cattle. The amount of bacterial synthesis and the efficiency of absorption of nutrients synthesized by the microorganisms are lower in the horse than in the cow.

Forages are the fiber portion of the horse’s diet and are fed either harvested as dried hay or  unharvested as pasture. One reason the fiber is necessary in a horse’s diet is for use as a source of energy for the microorganisms in the cecum and large intestine. The by-products of microbial fermentation provide a source of digestible energy for the horse. The indigestible portion of the fiber is needed by the horse for maintaining normal pH in the digestive tract and also for keeping the GI tract functioningas it should. The indigestible fiber also helps to fill the gut so that intake of carbohydrates is not too rapid. Rapid intake of cereal grains, which are high in carbohydrates, could cause colic, diarrhea, and acute laminitis. 

Feeding an inadequate amount of forage to horses that aren’t on pasture will not only increase the risk of diarrhea, colic and founder; it will also result in behavioral problems. Just like a bored child, horses with nothing to do are more likely to develop negative behaviors. They will chew on wood (crib), suck wind, head bob or weave, and chew on other horse’s manes and tails to name just a few annoying and destructive habits. Wood chewing can be an especially big problem for your horse and your barn. Not only can a wood chewing horse do some major damage to your barn and fences, it can also result in splinters in the mouth and throat, or cause intestinal obstructions that could be fatal. 

Harvested forages must be high quality and free from weeds, dust and mold. It should be green and leafy with fine stems and smell nice and fresh. Moldy or dusty hay is of no nutritional value and will cause more problems than it is worth. Dusty hay is often associated with respiratory problems such as heaves (Chronic obstructive pulmonary disease), an allergy to the fungal spores in hay or bedding.

Hay can be of either the grass or legume variety. Timothy, orchard, brome and Bermuda grasses make excellent grass hays. They are very palatable and less likely to be dusty or moldy than legumes although the nutrient content is lower. Legumes such as alfalfa are higher in nutritional value and generally contain 2-3 times more protein and calcium and more soluble and non-fiber carbohydrates then grass hays. Because of the increase in these nutrients legumes are the preferred hay during lactation, pregnancy and growth. If given free access most horses will consume more legume hay than grass hay, in part because legumes have nice green leaves and tender stems. No matter what kind of hay you are feeding, the amount the horse will consume is directly related to the hay quality.