Managing Grazing of Horses
David W. Freeman, Extension Equine Specialist
These are simple questions with not so simple answers. In order to maximize utilization of pastureland, you need to understand how horses utilize forage, factors affecting animal performance on pastures, and the grazing behavior of horses. Combining these "animal factors" with agronomic principles will allow you to set realistic goals and design pasture plans to help meet those goals. This fact sheet outlines several considerations for managing "animal factors" that will help ensure that horses get the most from forage. Additional information can be obtained from OSU Extension Facts F-3980 "Use of Forages for Horses" and OSU videotape VT-188 "Forage Use for Horses."
Intake Limits of Horses on Forage Diets
Information on expected intake of different types of forage assists in determining stocking rates and estimating animal performance. Mature horses on an all-hay diet can consume between 2 and 2.5 percent of their body weight daily in hay dry matter. Therefore, in situations where hay is full fed and highly palatable, a mature 1 200-pound horse can be expected to consume as much as 30 pounds of hay per day to maintain body weight and condition. When exercised or in states of production such as lactation, physiological needs can quickly overwhelm the ability of an all-hay diet to supply all the necessary nutrients. In such instances, it becomes necessary to supplement the diet with grain.
Determining a horse’s intake of forage when grazing on a pasture is more difficult. Limited information suggests that dry matter intake on pasture is similar to the dry mailer intake expected on all-hay diets. New Zealand researchers have reported dry matter intakes of pregnant mares on pastures to be about 1.7 percent of body weight per day. Dry matter intakes increased to 2.4 percent of body weight per day during lactation. While pasture quality allowed for adequate digestible protein intake during the study, energy intakes were 10 to 20 percent lower than the estimated requirements.
Generally, the average intake of horses grazing on pastures can be expected to resemble those of horses that are fed hay. However, average intake estimates mean little because many factors can affect them. These factors include a horse’s preference for a different species of forage, differences between monoculture pastures and multi-forage pastures, the stage of growth of available forage, and the availability of supplemental feed.
Another way of expressing a horse’s preference for different types of forage is the term "palatability." Small grains, annual and perennial ryegrass, bluestems, and bermuda grass are highly palatable for most horses. Recent research from Georgia suggests that ryegrass, wheat, oats, rye, and triticale are acceptable to horses, with ryegrass, wheat, and oats being most preferred. Palatability trials on clovers suggest that crimson, berseem, and subterranean clovers are readily acceptable, while arrow leaf clovers are less acceptable.
Your horses may prefer different types of forage than another farm’s horses because of the factors that affect palatability. Monoculture pastures to which horses have become accustomed may be highly palatable, while the same forage species in a multi-forage pasture may go ungrazed. Given a choice and time, horses will pick and choose one forage over another. The order of palatability can change as the pasture is grazed down and as the changes of season affect the growth of different types of forage. Also, horses raised on one forage may show a greater acceptance for that forage
than horses without previous exposure to the same forage. Forage preference is one reason for high incidences of spot grazing in horse pastures.
Forage Nutrient Utilization
As indicated by research and casual observation, all-forage diets can supply the nutrient needs of several classes of horses. Availability of sufficient amounts of high-quality forage i~ usually the limiting factor. The two nutrients of most concern are energy and protein.
Compared to cattle, horses have less ability to digest energy in high-quality forage. When consuming high-quality forage, horses will compensate for slightly lower digestion and faster passage rates by maintaining a higher voluntary intake of dry matter. However, high amounts of forage lignification (mature, stemmy forage) decreases digestibility dramatically. Energy digestibility coefficients for forage range from more than 50 percent to less than 30 percent as the quality of forage decreases. Similar ranges of forage quality may affect energy digestibility in cattle two or three percent, compared to 10 to 20 percent in horses.
Protein digestibility of hay typically ranges from 50 to 70 percent. Protein digestibility of forage in pastures would be expected to be similar to various varieties of hay of like maturity. As with energy, the digestibility of protein in forage can be expected to vary between species and within one species at different stages of growth. One research trial calculated the protein digestibility of bermuda grass at 57 percent, low-quality alfalfa at 66 percent, and high-quality alfalfa at 73 percent.
Of added significance is the site of protein digestion within a horse’s digestive tract. The protein in forage is more efficiently digested and more highly utilized when digested in the small intestine than in the large intestine. Even though estimates for total tract protein digestibility are similar for low- and high-quality alfalfa, protein in low-quality alfalfa is digested primarily in the large intestine. Comparably, almost one-third of the protein in high-quality alfalfa is digested in the small intestine. Maximizing digestion in the small intestine becomes of significant importance when meeting the needs of growing and producing horses.
Forage is also a good source of minerals and vitamins. As a general rule, the balance of calcium to phosphorus is appropriate, although absolute amounts of the two minerals may be deficient for some phases of horse production or growth. A commonly recommended practice for horses on pasture is to provide a mineral supplement with equal parts of calcium and phosphorus to guard against deficiencies. Mineral content of forage will vary between different forage species and in similar types of forage at different stages of growth and growing locations. Agronomic practices such as fertilization will alter mineral profiles of forage.
Estimating Correct Stocking Rates
Proper stocking rates (the number of horses per unit of land area) are affected by several factors, such as forage species, season of the year, environmental moisture, fertilization, and length of time that horses have access to the pasture. In one trial conducted with yearling horses on bermuda grass pasture, a forage allowance of 50 pounds of dry matter per 100 pounds of live weight provided maximum average daily gain. Denser stocking rates greatly reduced the average daily gain. Yearlings on properly stocked, high-quality, well-managed bermuda grass can be expected to gain 1 to 1.2 pounds of body weight per day, which is equal to moderate growth rate recommendations for yearlings. Expected gains on small grains are less for yearlings (.8 to 1 pound per day), possibly due to the intake of large amounts of water. If the amount of water consumed is large enough, water fill may reduce dry matter intake and hinder the rate of growth.
The availability of supplemental grain has been shown to affect yearling growth both positively and negatively in several grazing trials. Yearling gains on properly stocked, well-managed bermuda grass pasture have been improved slightly when grain is supplemented at one percent (6 to 8 pounds) of body weight per day. However, it is interesting to note that yearling gain was decreased in one trial in which half of this amount was fed. The probable cause was that the behavior was altered because the yearlings spent more time waiting around feed troughs. The benefit of the grain did not offset the lower forage intake caused by spending less time grazing. Supplemental feeding of yearlings on small grain pastures appears to be of more value for increasing performance. While supplementation has been shown to increase gains only slightly in yearlings on well-managed bermuda grass, gain differences of similarly supplemented yearlings grazing small grains have been doubled (.8 as compared to more than 1.5 pounds per day).
Considerable forage management accompanied the previously mentioned research. Higher stocking densities, multi-species pastures, and seasons of the year when forage is not in an active state of growth are examples of factors that severely limit expected animal performance.
Usually, forage height is too short on horse farms because of overgrazing. This not only limits forage production, but also dramatically affects forage intake by the horse. Research in Texas suggests that average daily gain of yearlings is severely reduced any time the herbage height of bermuda grass decreases below three inches. This is related to the availability of leaf and stem portions of the plant. The top layer of a pasture has a higher leaf content. To maintain horse performance and forage growth, it is important to allow a pasture to
develop adequate leaf area before grazing, and then provide a periodic rest from grazing so that the pasture can recuperate.
As previously noted, nutrient content and digestibility can be expected to decrease as the forage becomes mature. Some species of forage, such as bermuda grass, have rapid growth rates when environmental conditions are optimal. As a result, grazing will need to be regulated in order to maintain acceptable heights in some pastures at certain of the year. The recommended height for bermuda grass is between two and six inches during grazing periods.
Stocking rate recommendations based on unit amounts of forage per unit amount of animal can be difficult to understand. Usually, requests are made for stocking rates based on the number of horses per land area. However, differences in horse weight and available forage make it difficult to give recommendations for specific situations. Under controlled circumstances, stocking rates as intense as one mature, non producing horse to ito 1 .5 acres of thick, productive bermuda grass at four to six inches of growth have been successful. The same stocking rates on small grains would require six to seven inches of plant growth. Pastures that have less dense or shorter forage or those that are not as intensively managed will require more acreage per horse. If horses are kept in unimproved, native grass pastures, it is common that they will require five to 10 acres per horse.
Grazing Behavior and Forage Utilization
Horses seem to do more damage to pastures than other types of livestock. Pastures grazed by cattle seem to be more uniformly grazed, are not overgrown with weeds, and are not overgrazed as quickly. Many of these observations are true because horse pastures tend to be overstocked.
These observations are also true because the management of horse pastures is more difficult and intensive than that of cattle. Horses clip plants off close to the ground, causing severe problems for plant regrowth. Also, horses will trample congregation areas to the extent of killing all forage and creating a sacrifice area. Some horses tend to defecate in localized areas which causes manure buildup and reduces the palatability of forage.
Probably the most difficult behavioral trait to overcome is a horse’s selective grazing instinct. Horses selectively graze because of the palatability of different types of forage and because of the different stages of maturity of a specific forage. Horses will also selectively graze immature forage. Selectivity results in spot grazing which reduces intake of quality forage. This is a vicious cycle because horses will overgraze areas with short, new growth, while mature forage continues to grow past the point of desired palatability. As
desirable species of forage are grazed out, weedy species tend to increase. Thus, horses can quickly turn a pasture into a weed patch or dry lot.
Use of controlled grazing
Many horse farms can benefit from some type of controlled grazing system. It is advisable to control spot grazing or overgrazing by dividing large areas into smaller grazing cells. Allowing for rest periods from grazing can increase total forage production and will help sustain higher stocking rates. Removing horses from pastures part of the day or rotating horses from one pasture to another are practices that will provide rest periods. Scheduled access to pastures can be implemented around other farm routines, such as morning and evening feedings. This would allow horses to graze for 10 to 12 hours between feedings. Shorter grazing periods would be required in times when forage supply and production are limiting factors.
Rotational grazing plans require the use of more than one pasture. Many farms using continuous grazing as the only grazing system can easily divide large pastures into two or more grazing cells by the use of temporary fencing. Typical fencing alternatives include multi-wire electric fencing or electrified poly-tape. Horses placed behind temporary fencing must be adapted to it. Use of temporary fencing in large areas will allow horses to become accustomed to it before being confined to smaller grazing cells. Improving visibility of temporary fencing by tying ribbons on wires and posts or by using such products as poly-tape will help ensure safety. It should be remembered that horses cannot be stocked as densely as other species of livestock because of their high level of aggressive behavior toward one another. Thus, the use of small grazing cells for large numbers of horses has its limitations.
Recommendations for Managing Grazing
This fact sheet focuses on grazing considerations. For more information on forage species selection, fertilization, weed control, and mowing, contact your Cooperative Extension office.
Several recommendations relative to managing grazing of horses are provided as a summary below.
It may not be feasible to implement many grazing management practices because of limited land area or other constraints. Regardless, few farms use grazing and forage management techniques to their potential.
Visit: Oklahoma State University for more information on the health of your horse.