Equine nutrition

Equine nutrition is the feeding of horses, ponies, mules, donkeys, and other equines. Correct and balanced nutrition is a critical component of proper horse care. Horses are non-ruminant herbivores of a type known as a 'hindgut fermenter.' Horses have only one stomach, as do humans. However, unlike humans, they also need to digest plant fiber (largely cellulose) that comes from grass or hay. Ruminants like cattle are foregut fermenters, and digest fiber in plant matter by use of a multi-chambered stomach, whereas horses use microbial fermentation in a part of the digestive system known as the cecum (or caecum) to break down the cellulose. In practical terms, horses prefer to eat small amounts of food steadily throughout the day, as they do in nature when grazing on pasture lands. Although this is not always possible with modern stabling practices and human schedules that favor feeding horses twice a day, it is important to remember the underlying biology of the animal when determining what to feed, how often, and in what quantities. The digestive system of the horse is somewhat delicate. Horses are unable to regurgitate food, except from the esophagus. Thus, if they overeat or eat something poisonous, vomiting is not an option. They also have a long, complex large intestine and a balance of beneficial microbes in their cecum that can be upset by rapid changes in feed. Because of these factors, they are very susceptible to colic, which is a leading cause of death in horses. Therefore, horses require clean, high-quality feed, provided at regular intervals, plus water and may become ill if subjected to abrupt changes in their diets. Horses are also sensitive to molds and toxins. For this reason, they must never be fed contaminated fermentable materials such as lawn clippings. Fermented silage or 'haylage' is fed to horses in some places; however, contamination or failure of the fermentation process that allows any mold or spoilage may be toxic. Horses and other members of the genus Equus are adapted by evolutionary biology to eating small amounts of the same kind of food all day long. In the wild, horses ate prairie grasses in semi-arid regions and traveled significant distances each day in order to obtain adequate nutrition. Therefore, their digestive system was made to work best with a small but steady flow of food that does not change much from day to day. Digestion begins in the mouth. First, the animal selects pieces of forage and picks up finer foods, such as grain, with sensitive, prehensile, lips. The front teeth of the horse, called incisors, nip off forage, and food is ground up for swallowing by the premolars and molars. The esophagus carries food to the stomach. The esophagus enters the stomach at an acute angle, creating a one-way valve, with a powerful sphincter mechanism at the gastroesophageal junction, which is why horses cannot vomit. The esophagus is also the area of the digestive tract where horses may suffer from choke. (see Illnesses related to improper feeding below) Horses have a small stomach for their size, which limits the amount of feed that can be taken in at one time. The average sized horse has a stomach with a capacity of only 4 US gallons (15 l), and works best when it contains about 2 US gallons (7.6 l). One reason continuous foraging or several small feedings per day are better than one or two large meals is because the stomach begins to empty when it is two-thirds full, whether the food in the stomach is processed or not.