Hay

Horses are herbivores, animals made to live primarily on plants (forages). About 65 percent of the digestive capacity of the horse is in the lower gut, or the cecum and colon. The cecum and colon contain large microbial populations which allow for the digestion of fibrous feeds, much like the digestive tracts of cattle and sheep (ruminants). Evidenced by the size of the lower gut and the presence of bacteria, the horse is designed to digest primarily forages. Horses have fewer digestive upsets and behavioral vices, such as wood chewing and cribbing, when hay is the main portion of the ration. For proper digestive tract function, horses require a minimum of 1 percent of their body weight per day in long-stem dry matter. This can be done in any form that is convenient and economical. When the total ration particle size is below 1 inch in size, problems with rate of passage, digestibility, and behavioral vices occur. Forages are most healthfully offered as pasture during the growing season. Conditions such as limited acreage, low productive pastures, seasonal rainfall variations, and the need to house horses separately or indoors restricts the ability to utilize pasture and necessitates the feeding of hay as the primary forage. In order for pasture to provide the majority of the nutrients for a horse, at least two acres should be allocated per horse. Under most situations, rations are more economical when based primarily on hay rather than on concentrate mixtures to provide the bulk of the nutrients. The horse requires an absolute amount of specific nutrients per day, regardless of the feedstuff. The value of hay is determined by the composition of nutrients in the hay rather than the hay's appearance. The closer the nutrient composition of the hay matches the requirements of the horse being fed, the fewer supplements needed and the more economical the total ration. Traditional Selection Criteria Forage quality is an expression of the characteristics affecting consumption, nutritive value, and resulting horse health and performance. Even though many factors affect forage quality, no single factor, including color, can be used to make predictions. Maturity stage at harvest, forage species and variety, leafiness, harvest and storage conditions, and the presence of foreign objects, weeds, and pests are all important factors affecting quality. A closer examination helps the horse manager economically select the best hay for their situation. Color The vitamin A precursor in plants is greater when hay is green. A beige color is an indication of sub-bleaching and leaching of nutrients by rainfall that occurred after harvest. Color is a poor indicator of forage quality as bright green weeds may have lower nutrient composition than brown alfalfa. Maturity Plant maturity is visually determined by the amount of seed heads of grasses or the flowers of legumes present at the time of harvest. Forages in the vegetative stage will not have visible seedheads or flowers. As plants progress through seedhead and flower bud emergence, pollination, and seed formation, the concentration of structural carbohydrates and lignin increases and crude protein decreases. The structural carbohydrates, cellulose, and hemicellulose are partially digested by the bacteria in the horse's lower gut, but lignin, another component of plant fiber, is not digested at all. As lignin increases one percent, the digestibility of the forage dry matter decreases three to four percent. Forage digestibility is indirectly measured by determining the level of acid detergent fiber (ADF) in the hay. As the plant matures, ADF (cellulose and lignin) increases, and digestibility decreases. Neutral detergent fiber (NDF), a measure of cell wall content, increases as the plant matures and is an indirect measure of how readily a forage is consumed. Immature hay is more easily digested by the horse (lower ADF percent) and more readily consumed (lower NDF percent), thus it is worth more to the horse owner. The maturity of the plant is not related to a particular cutting, but rather to the stage of maturity of the plant when cut.