Grazing systems employ the basics of grazing management to help producers accomplish their operational goals. Depending on what grazing system you choose, you may improve pasture conditions, increase forage use, or enhance livestock production. Four of the most common grazing systems are described below.
Merrill (Three Herd, Four Pasture) Deferred Rotation
The Merrill grazing system, shown in figure 1, was developed in southwest Texas and is applicable to other rangeland environments where effective precipitation and plant growth can occur anytime. Under this grazing system, the ranch is divided into four grazing pastures with three herds. At any given time, three pastures are being grazed while the fourth pasture is allowed to recover. Three of the four pastures are grazed year-round. Each year one pasture has a four-month deferment period, which is rotational among the four pastures; by the end of a four-year grazing period, each pasture has been rested during each season of the year. In effect 100 percent of your livestock graze 75 percent of the land base each year. Carrying capacity needs to be within 10 percent among the four pastures for the system to work correctly.
This system favors individual animal performance through low stocking density and light to moderate grazing pressure, as well as relatively little movement of cattle through pastures.
The switchback grazing system takes relatively little management. It includes two pasture units and one herd. Grazing is alternated between units at one- to two-month intervals. Livestock are rotated to the deferred pasture when the forage in the pasture being grazed becomes limited.
A producer's major advantage is being able to determine forage shortfalls before needing to reduce stocking rate or beginning substitute feeding. The switchback method also allows the producer to confine livestock to a smaller area and monitor them more frequently. This system works well when the two pasture units are composed of two forage types (e.g., native and improved bermudagrass) because it allows the producer to manage them separately.
The switchback method favors individual animal performance resulting from low grazing pressure. It is easily adapted to a three- or four-pasture, single-herd, low intensity, rotational grazing system in which cattle are moved to the next best pasture available. Pastures are usually rested 60 to 75 percent of the time by using three or four pastures.
High Intensity, Low Frequency Grazing System
The high intensity, low frequency (HILF) grazing system, shown in figure 2, was initiated to improve pasture or range conditions of subhumid rangeland, rather than obtain high animal performance. The system requires multiple pasture units, more than five, with one combined herd. Grazing periods are moderate (more than fourteen days), and recovery time is beneficially long (more than ninety days). Throughout a given year, pastures are rested 70 to 90 percent of the time.
The HILF grazing system minimizes selective grazing and forces use of less preferred forage species by using high stocking densities and long grazing periods. Long deferment periods allow regrowth necessary for plant recovery. The long-term objective is pasture improvement relative to forage production and desirable species composition.
The HILF grazing systems do not favor individual livestock performance, but differences can be minimal with experience and the correct stocking rate.
Short Duration Grazing System (SDG) or Controlled Rotation Grazing System (CRG)
The SDG and CRG systems,figure 3, were developed and work best in areas that have at least three months of good weather for plant growth and over 25 inches of average annual precipitation. These conditions allow ample forage regrowth following the short, intensive grazing periods associated with SDG.
An SDG system involves numerous pastures (paddocks) with similar grazing capacities and uses a single combined grazing herd. The number of paddocks ranges from five to fifty per ranch, but the average is usually eight to twelve. Grazing periods are usually shorter than seven days, depending on the season, stocking rate of the paddock, desired recovery periods, and number of paddocks used in the grazing cycle. Rest periods for each paddock range from thirty to more than sixty days. Pastures are rested about 80 to 95 percent of the year. Herds should not be rotated on a calendar basis; proper grazing management has to remain flexible to account for conditions such as forage and changes in weather.
The principal factor influencing the length of the grazing period is the rate of forage growth. Generally, as forage grows more rapidly in the spring and early summer, grazing periods become shorter. As forage growth slows or ceases during the late summer, fall, and winter, rest periods become longer, since the forages cannot recover as quickly from grazing; thus, the grazing period length in the other paddocks increases.
When SDG systems are used correctly, forage is more efficiently harvested, forage quality is improved, and in some instances stocking rate can be increased. However, management has to realize this system requires a high level of skill and good understanding of pasture and livestock management to achieve good results. For successful implementation of an SDG system, producers should begin conservatively and advance toward a higher degree of complexity as experience allows. Other benefits of SDG include centralized cattle observation, accurate assessment of forage supply, greater livestock control, and ease of livestock management and handling. Successful implementation can mean improved livestock production on a per acre basis, often at the expense of individual livestock performance, which could change directly with skill and experience in using the grazing system.
Grazing systems combined with good grazing management skills have long enhanced overall production of livestock operations. Correct stocking rate is critical to the success of any grazing system. Before applying a grazing system to your operation, you must determine what system best fits your operation's goal and what level of management is available to operate it.
Larry spent two summers at the Noble Research Institute as a forage management intern while attending Oklahoma State University.