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Pasture Forages

In the U.S., pasture forages are a significant feedstuff in animal production. In the U.S., pastures provide approximately 36% of the feedstuffs consumed by animals.

Figure 8.11 illustrates the percentage of land per county as being pasture or rangeland as recorded in the 1987 Census of Agriculture. (Click on photo for larger image)

Effectiveness of pasture management is monitored via forage and animal production per unit of land. In the U.S., pastures are economically significant to the beef cattle, dairy cattle, sheep, and horse industries. In the U.S. beef industry, pastures are primarily used in cow-calf and stocker operations. In the U.S. dairy industry, pasture use is limited for lactating cows as a result of high nutrient requirements for milk production and limited land area of the operation. More often, pastures are used for dry-cows and heifers; given land area is available. In the U.S. sheep industry, pastures are a significant source of feed.

A pasture is simply defined as an area of land with forage grown for animal consumption via grazing. In general, pastures can be classified as either cultivated pasture or native pasture. Figure 7-4 on page 132 of the text illustrates the cultivated or introduced and the native pasture regions of the U.S. Cultivated or seeded pastures are defined as either receiving greater than 20 inches of rainfall per year or are irrigated. Examples of cultivated pastures include cultivated pastures of the Midwest, South, East, and irrigated in higher rainfall areas of the West.

Figure 8.12 illustrates sheep grazing a cultivated pasture.

Native pastures are defined as pastures receiving less than 20 inches of rainfall per year. Native species on native pastures are species that were not introduced and have existed for a period of time. In general, as a result of forages species and forage management, the nutritional value and yield of cultivated pastures is higher than the nutritional value and yield of native pastures. Further, pastures may be classified as permanent, semi-permanent, or temporary and supplemental. Permanent pastures are pastures used for many years. For permanent pastures, in general, pasture is the most profitable use of the land. The majority of rangelands are classified as permanent pastures. Semi-permanent pastures are used for a number of years and are a component of a crop rotation program. Temporary or supplemental pastures are pastures used for a short period of time. Temporary or supplemental pastures often include annual species.

The decision to include pasture and range forages in the forage system requires the consideration of a number of factors. A number of the advantages of pasture and range forages include: 1) reduced feed cost; 2) reduced cost of facilities, especially housing facilities; 3) given effective management, the forages may provide a relatively consistent feedstuff of high nutritional value; 5) improved animal health; and 6) pastures provide a productive means to use the land. A number of disadvantages of pasture and range forages include: 1) for some land, loss in revenue compared to alternative crops grown on the land; 2) animal management may be labor intensive in some grazing systems; and 3) the nutritional value of the forages depends, in part, on environmental and soil conditions.

Yield and nutritional value of pastures are influenced by a number of factors including plant species, environmental and soil conditions, stage of maturity, and grazing management. As a number of these factors were discussed earlier, the discussion in the next section, in general, will focus on the factors specific to pasture systems.

Grazing management controls the timing and amount of forage grazed to prevent: 1) a decrease in the number of, yield, and nutritional value of favorable species; 2) an increase in the number of unfavorable species; and 3) an increase in soil erosion. Broadly, grazing management systems are classified as either continuous or intermittent (i.e. rotation).

Continuous grazing is uninterrupted grazing of the pasture throughout the grazing season. In comparison to rotation grazing, continuous grazing requires a lower stocking rate, a variable stocking rate throughout the season, and larger pastures. During periods of adequate forage yield and nutritional value, continuous grazing may be as productive as rotation systems. Advantages of continuous grazing are: 1) lower fencing and watering costs; 2) lower labor costs; and 3) less knowledge of forage management. The disadvantages of continuous grazing are: 1) variable stocking rate may be an issue; 2) difficult to manage favorable and unfavorable forage species; 3) more difficult to harvest and store excess forage; and 4) supplementation required to compensate for forage deficits.

Rotation grazing is a system where two or more pastures are grazed and rested in a planned sequence. The primary factor to consider is time; time of grazing and time of rest for the pasture. Time of grazing and time of rest are determined by forage growth and animal consumption. Forage growth is influenced by factors such as soil and environmental conditions. Rotation grazing systems promote nutritional value and yield of the forage over time. During less productive time periods, rotation grazing systems are more productive compared to continuous grazing systems. The advantages of rotation grazing are: 1) increased yield and nutritional value of forage; 2) improved stand persistence; 3) facilitates removal of excess forage as silage or hay; 4) increased carrying capacity of the land; 5) promotes equal defoliation; and 6) reduced incidence of animal disease. Disadvantages of rotation grazing are: 1) higher capital costs; 2) higher labor costs; and 3) more knowledge of forage management. One example of a rotation grazing system for cultivated pastures is intensive rotation grazing.

In addition to the primary forage species discussed, there are a number of additional forages used as pasture forages. Rape and kale are grazed by sheep. Beets and turnips are grazed by cattle and sheep. As winter pastures, cereal grains may be grown for forage. As supplemental summer pastures, annuals may be grown for forage. Crop residues may be grazed by animals following harvest. Crop residues include stover, chaff, straw, stalkage, and huskage.

Figure 8.13 illustrates cattle grazing corn crop residue.

In general, the forage residues are grazed by animals with lower nutrient requirements and the animals require supplementation with protein and the various micronutrients.

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