Grass is the natural food of horses. It is provided for him without the interference of art. It is composed of a great number of plants, differing much or little from each other in structure, composition, and duration. Some of the natural grasses are to the horse mere weeds, destitute of nutriment, though not positively injurious. Several are rejected, or eaten only when there is nothing else to eat, and none are sufficiently rich to maintain the horse in condition for constant work, even though the work be moderate. At a gentle pace he may travel a few miles to-day, but he is unfit for a journey to-morrow. By cutting the grass and bringing it to the stable, the horse may be saved the labor of collecting it; but still he can render very little service.

Grass, however, or green herbage of some kind, is given to almost all horses during a part of the year. The young animals, from the time they are weaned till they are fit for work, receive grass as long as it can be had Hunting and racing colts excepted, they receive little else.

It is commonly believed that grass has some renovating and purifying properties, not possessed by hay nor by grain. It is true that all the kinds of green herbage, including clover, saintfoin, lucerne, tares, and ryegrass, produce a change upon the horse. But whether the change be for better or for worse, is another question. For the first two or three days, green food relaxes the bowels and increases the secretion of urine and of perspiration. Very often it produces an eruption on the skin, particularly when given along with a large allowance of grain. When the horse is permitted to eat what he pleases, the belly becomes large. These effects may be termed immediate. They are most apparent at the commencement, but are visible so long as the horse receives any considerable quantity of grass. Green food produces other effects not so easily traced. Wounds heal more kindly, inflammatory diseases are not so fatal, and chronic diseases frequently abate, or they entirely disappear under the use of grass. The horse, however, is always soft, when fed much on green food.

He sweats a great deal, and is soon exhausted by his work.