Practical use and common-sense judgment has shown that horses can survive and do well on forages alone. There are ranges of survival and ranges of just how well horses do on various forages. It has only been recently that research and demonstration work has set out to define these ranges and how they can fit into the nutritional needs of the horse, which vary enormously. The following comments are based primarily on winter forages and bermudagrass, with additional information on other forages.
Performance on Bermudagrass, Winter Pastures, Kliengrass and Alfalfa
The quantity of forage available influences gain of livestock, including horses. Grazing that allowed 60 to 100 pounds or more of dry matter pasture per 100 pounds of body weight resulted in maximum individual performance, according to Aiken et al. (1985) and Roquette (1985). In our experience, good thick bermudagrass for one 1,000-pound horse per acre meant only 4 to 6 inches of growth above the soil line. For our good small-grains-based winter pasture, we would need 6 to 12 inches for one 1,000-pound horse per acre for upper-level gain. If the pasture is shorter and the quantity lower, the horse must have more area to get 60 to 100 pounds of forage per 100 pounds of body weight and reach top gains. At least two more acres are required in some cases. If the forage is extremely short, that expanded acreage still will not allow convenient intake for upper-level gains.
In a 201-day trial, yearling horses produced 1.12 and 1.46 pounds of ADG from pasture only versus pasture and 8.3 pounds of 14 percent crude protein feed per head per day (Roquette, 1985). The pasture was sod-seeded winter pasture of rye-ryegrass-clovers in bermudagrass and then pure bermudagrass during summer. The winter pasture phase lasted two to three months in early spring, with the bermudagrass continuing to October. The horses on pasture and feed gained their advantage during the high-quality winter-pasture phase, with ADG the same on pasture only versus bermudagrass pasture and feed during the summer. Horses on winter pasture only may not have reached their forage gain potential because of the high moisture content of the winter forage, which is often 80 percent or higher. Horse growth, other than pounds of gain, was essentially the same in both treatments. Horses had body condition scores of 4.2 versus 5.9 from pasture only versus pasture and feed.
With advances in age and stage of bermudagrass growth, there was increased selective and spot grazing. This phenomenon is often seen in pastures, and although it was not quantitatively measured, forage managers understand that plant selection and spot grazing results in reduced quantity and quality intake and therefore lowered performance. Spot grazing can be defined as overgrazing and reduced quantity available per body weight unit. Stock, including horses, tend to try to get their fill on that short spot, cannot, and to an extent then go hungry. They will not eat the taller, less preferred areas. One reason for rotational grazing and management is to limit selective and spot grazing, thereby creating more uniform grazing, better forage quantity and quality control, and better stock performance.
Horses on pasture and feed tended to wait for feed and not graze actively, a common characteristic of forage and feed situations. Unfortunately, it likely limits performance from the pasture itself.
Aiken et al. (1985) compared horse performance from stocking rates on bermudagrass. The data showed that, in general, the heavier the stocking rate, the lower the horse gains. Daily gains ranged from a loss at heavy stocking rates to 0.95 pounds of ADG at light stocking rates. Frame growth was the same from all stocking rates. At a certain point, lighter stocking rates induced selective or spot grazing and then lower gains, apparently because of lower forage quality (figure 2). The greater the forage volume per acre, the greater the spot grazing.
Some related information by D. E. Johnson et al. (1982) and B. L. Koller et al. (1978) showed that digestibility of hay was 12 percent less in horses than cattle and that horses consumed 40 percent more dry matter per unit of body weight than cattle. This restresses that both quantity and quality have an important influence on horse performance from forages.
Webb et al. (n.d.) reported that yearling horses grazing bermudagrass gained 0.92 pounds per day, while those on kleingrass lost 1.56 pounds per day. The apparent reason for the negative performance was kleingrass's low palatability for horses, which resulted in an intake only 19 percent that of bermudagrass. Horses do not like mature switchgrass.
Evaluation of alfalfa for yearling horse pasture by the Noble Research Institute and Oklahoma State University illustrates some of its potential. In the twenty-five-day test, horses in continual grazing gained an average of 0.52 pound per day, whereas horses in a six-paddock rotational grazing unit gained 1.30 pounds per day (Freeman et al., 1987). Other growth characteristics were satisfactory, and there were not any forage-related horse problems.
Whether any of these gains and other performances are acceptable depends primarily on the goal for the young horse. Some goals may be met from pasture only, with adequate frame growth and an ADG of 1 pound per day, while other goals requiring a higher gain and condition performance mean some feeding is necessary.
Palatability in this case is how horses relish and consume various forages. Given a choice and time, all stock will choose one forage over others, and observations show that the order of palatability changes as plants are grazed down and stage of growth or season proceeds. Palatability is important in that grossly unpalatable forages may present a problem through insufficient forage intake. The reverse is that very palatable forages increase dry matter and nutrient intake and enhance horse maintenance or gain performance. To some extent, you should consider palatability when planning horse pastures.
It is common for medium- to low-palatability beef cattle forages to be consumed like more palatable forage if the pasture is a monoculture or close to it, or if good rotational grazing is practiced where stock densities are relatively high.
A key to managing forages with variable but acceptable palatability is to use rotational grazing methods because the animals are only briefly on a paddock whose stock density does not allow extensive picking and choosing. Therefore, in a relatively short time, they eat what is reasonably acceptable to them.
Beef cattle rotations have been managed on grass mixtures when graze-off of forage in a given paddock was accomplished in one-half to three days with no obvious signs of undesirable selective grazing caused by palatability differences. However, extremely short grazing periods of one-half to one day to use all forage may not be realistic for horses. The cattle didn't have time to sort out palatable plants. They ate what was there in a hurry. Also keep in mind that horses are not (1) intelligent enough or (2) intuitive enough to balance a diet on the basis of forage palatability. A cafeteria of forages may not be totally helpful in balancing horse forage rations.
Most horsemen and others who have observed pasturing horses know that small-grain pastures, ryegrass, lush bermudagrass, crabgrass, certain Old World bluestems, and other grasses are all well used by horses. Research illustrates the relative palatability of southern forages to horses (Ball, 1985; table 2).
Palatability will change with different horses, season, and stage of pasture growth. Arrowleaf clover rated low in palatability in this study, but it can be used some in a grass-clover mixture in rotational grazing situations. Palatability is important, but not the last word. Archer (1973) of the United Kingdom has researched horse forage palatability. Many of the forages he tested are not important here, but results for some forages we also have in the United States are presented in table 3.