Pastures: Pasture Systems
Developing a pasture system that uses your land resources and fits in with your total animal, forage, and crop program is an important first step in pasture management. A major goal in pasture management is to provide quality pasture for the grazing animals throughout the grazing season. By using the various growth patterns of the many pasture species grown in Pennsylvania, the grazing season can last from April to December (Figure 1.8-1).
Permanent Cool-Season Pasture
In most cases, permanent cool-season pasture is land not suitable for crop production because of poor soil characteristics or topography. These sites often are overgrazed and underfertilized. With proper management, these pastures can provide significant amounts of forage for many dairy and livestock farms. Kentucky bluegrass, the species most tolerant of close grazing, is the cool-season grass commonly found in permanent pasture.
In addition, more productive forage species such as tall fescue or reed canarygrass can be grown on permanent pasture sites, often with a legume. Other grasses also may be found in permanent pastures, but they do not persist as well.
Semipermanent Cool-Season Pasture
When properly managed, most perennial cool-season legumes and grasses grown for hay and silage also can be used for pasture. Often these pastures are incorporated into the crop rotation and, when grown on good soils and properly managed, can be very productive.
Warm-season perennial grasses, including switchgrass, big bluestem, and Indiangrass, grow well from mid-June through September, can provide adequate pasture when cool-season pastures are inadequate, and are especially suited for beef cattle.
Grown in rotation with other crops, annual pastures containing brassicas, small grains, or summer-annual grasses can provide supplemental spring, summer, or fall grazing.
Deferred or Stockpiled Pasture
This practice leaves paddocks or pastures ungrazed during certain seasons, to accumulate forage for grazing needed when pasture production is not sufficient to maintain the herd or flock. For example, some forages, such as birdsfoot trefoil or crownvetch, can be “stockpiled” in the spring to be grazed during the summer slump in pasture production. Other forages, such as birdsfoot trefoil or tall fescue, may be stockpiled in late summer for late fall and winter grazing. In this way, grazing is made available during seasons when low productivity of pastures might force the producer to sell cattle or feed hay. For more information about stockpiling forages, refer to Agronomy Facts 41: Strategies for Extending the Grazing Season, available from your local extension office.
Designing a Pasture System
After considering which species to grow and which pasture components to use, calculate the forage requirements of your herd or flock. Dry matter forage intake varies by animal species and class and is often influenced by what forage is offered and how much. To determine stocking rate and carrying capacity, animal units often are used; these figures provide a much better measure of pasture required than do actual animal numbers.
One animal unit is based on the daily forage intake of one 1,000-pound dry cow (about 25 pounds of dry forage per day). Table 1.8-7 gives some typical animal unit values for various species and classes of livestock. For information about pasturing horses, refer to Agronomy Facts 32: Pasture and Hay for Horses, available from your local extension office.
Estimating the acreage required to pasture a herd or flock depends not only on the animals’ feed requirements, but also on available forage produced. Pasture growth depends on plant species, soil characteristics, topography, fertilization, temperature, and soil moisture. Because of the variability in pasture growth, we can only estimate the amount of pasture required for grazing animals. Table 1.8-8 lists estimated acreages required for grazing animals on various types of pasture.
To estimate how much pasture a herd or flock will need, use Table 1.8-7 to calculate the total animal units of the herd. For example, if a beef herd contains 25 dry cows weighing 1,300 pounds each and 15 heifers at 550 pounds each, there are 47.5 animal units (AU) in this herd.
25 cows x 1.3 AU per cow = 32.5 AU + 15 heifers x 1.0 AU per heifer = 15.0 AU
Total AU for herd = 47.5 AU
Second, use Table 1.8-8 to estimate how many acres the herd will need during each month of the grazing season. If the herd will be grazing low-producing Kentucky bluegrass and white clover pasture in May, approximately 57 acres is needed to support the herd.
47.5 AU x 1.2 acres per AU = 57 acres
The same herd grazing high-producing Kentucky bluegrass and white clover pasture would need only approximately 19 acres during May.
For more information about designing a pasture system, refer to Agronomy Facts 43: Four Steps to Rotational Grazing, available from your county Penn State Cooperative Extension office.