Pasture may be in a small holding paddock, a run, or a large paddock. You must decide whether to use the area for exercise, forage, or both. Small, congested exercise areas and runs are not usually feasible to manage for forage production. Don't waste time or money on them, but do manage them to maintain a vegetation cover for soil conservation.
Horses require at least 2 acres per animal for a good exercise and forage area in good forage country. The stocking rate in southern Oklahoma probably varies from 2 to 5 acres per horse on improved pasture that is well managed.
A well-nourished horse will consume about 2 percent of its body weight per day on a dryweight basis. Thus, a 1,000-pound horse will require approximately 20 pounds of forage or feed per day, or almost 4 tons of dry matter yearly per horse.
A pasture can supply at least some of that forage, depending on the pasture and the horse needs. Bermudagrass and winter pasture in southern Oklahoma will produce 3,000 to 8,000 pounds of forage per acre with recommended minimum to moderate fertilization and adequate forage management. The 3,000-pound yield is enough bermudagrass for a 1,000-pound horse for the equivalent of 150 days. Therefore, about 2.5 acres would be needed to carry the horse on pasture and hay alone at a moderate level of agronomic management. The 8,000-pound yield could provide grazing for about 1.5 horses per acre for an eight-month equivalent, but the stocking rate is not even throughout the time.
Stocking density is the number and weight of the stock (horses) on a given paddock (pasture) while the herd is in that paddock. Stocking rate is the number and weight of stock (horses) on the whole pasture unit. Stock density rates vary extremely. One guide is that small groups of about ten mature horses in small rotational pastures tend to be better for pasture management than larger groups in larger pastures. Larger groups tend to divide into smaller groups and cause problems such as stampeding through fences. Sometimes the figure is much higher and the stocking rate still successful, especially in larger paddocks.
Direct cost of producing bermudagrass might be about fifty dollars per acre yearly. Thus, pasture cost per grazing day would be about thirty cents. This figure is highly variable. It represents a direct pasture cost for fertilizer and weed control of about twenty-five to thirty dollars per ton of forage produced.
The direct cost of producing an acre of good, small-grains-based, winter pasture ranges from about seventy-five to one hundred twenty-five dollars per acre. These forages, or mixtures, usually produce 2 to 3 tons of dry weight forage per acre yearly. Forage cost per ton varies from twenty-five to sixty dollars. The daily cost per 1,000-pound horse feed-day ranges from about twenty-five to sixty cents, which is economical compared with a fully hand-fed ration. These forages are very high quality.
Pasture quality is influenced by plant species and age, soil fertility, seasons, and drought, among other factors. Every forage we mention can be good quality. Soil fertility can be managed easily to enhance forage quality. An overabundance of forage can cause problems for many managers. The goal of pasture management should be to use fresh regrowth. Forage that has regrowth four to six weeks old and 4 to 10 inches tall is usually of excellent quality. Managing to graze at these stages is part of rotational grazing management discussed elsewhere.
These growth and recovery periods are worthy goals, but there will be much variation.
Remember, the better the quality, the better the cost offset from fully hand-fed rations. A so-called green pasture is not necessarily good. Horses can be malnourished in deep, green forage. Extremely lush pastures containing over 85 percent water can be too wet and too low in fiber for good nutritional intake or high dry-matter intake. The horse simply has to intake too much water to get needed nutrition. Plentiful low-quality pasture can result in hay gut and horse digestive tract impaction. Thus, supplemental feeding on pastures is sometimes needed.
It is helpful to have a basic knowledge of the horse digestive system when interpreting feeding, grazing, and animal health relationships of the horse. It may be helpful to compare horses with cattle in this regard. Horses are cecal fermenters. The majority of the digestion of roughage is accomplished in the cecum, or large intestine. Forage enters the stomach first, is broken down, and passes on to the small intestine, where most nutrients such as protein, simple sugars, and fats are absorbed. Then the forage passes into the large intestine, where specialized bacteria break down cellulose into a usable form of energy. Cattle are ruminants, meaning that forage enters the rumen, a pre-stomach, first. In the rumen, specialized bacteria break down most components of the forage into simpler molecules. The bacteria use some of these nutrients in the feed. The digestive system of the horse requires high-quality forages, whereas that of cattle uses very low-quality forage the best. Digestive anatomy is why horses are driven to eat small meals of high quality forage and are such notorious spot grazers. The long, folded large intestine is also the reason horses are so susceptible to impaction colic when fed low-quality roughage. In general, horses make efficient use of forage as long as it is high quality. If it isn't, horses cannot perform to their potential unless they receive supplemental feed. A different digestive system is required if efficient use of low-quality forage is desired. Freeman (1996) provides additional information.