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Cultivated Pasture and Rangeland Forages

The first portion of the section will discuss a few of the management issues for cultivated or seeded pastures. Regarding forage species, in general, for cultivated pastures, grass-legumes mixtures are recommended.

Cultivated pastures require provision of adequate moisture to the forage. Often, adequate moisture is provided via irrigation of the pastures. Management of irrigation systems requires consideration for factors such as the method and frequency of irrigation, amount of moisture per application, and removal of excess moisture (i.e. field drainage).

In addition to irrigation management, irrigated pastures require a higher level of fertility to maximize yield and nutritional value. The type and amount of fertilizer applied is dependent upon plant species and production objectives. In general, the three main nutrients to consider are nitrogen, phosphorus, and potassium. In grass-legume pastures, nitrogen will promote grass growth and phosphorus will promote legume growth. In addition, as forage mineral composition is influenced by the composition of the soils, consideration should be given to minerals deficient in the specific soils.

To maximize profitability from a pasture with a high yield and nutritional value, it is recommended to graze the pasture with high-producing animals. Examples of high producing animals include lactating and growing cattle and sheep. Supplementation of the forage may also be required to maximize the nutritional value of the forage and improve animal production. Pastures maintained in a vegetative state, especially grass-legume mixtures and legumes, have a high crude protein content. In addition, the energy content of the forages is low relative to the protein. As described earlier, efficient synthesis of microbial crude protein requires a synchronization of a nitrogen and an energy source. Therefore, to improve microbial crude protein synthesis and animal production, animals consuming forages with a high protein content are often supplemented with an energy source.

Rangelands are large, naturally vegetated land areas.

Figure 8.14 illustrates sheep on a rangeland.

The range is managed with a rotation grazing system.

Figure 8.15 illustrates cattle grazing a rangeland.

In general, the vegetation consists of relatively low densities of grasses, legumes, forbes, and browse. Rangeland vegetation includes a combination of native and introduced species. In the U.S., the majority of rangelands are west of the Mississippi River. In addition, the majority of rangelands in the west are owned and administered by the United States Federal Government. In comparison to cultivated pastures, in general, rangelands are less productive regarding yield and nutritional value of forage and are more difficult to manage. In addition, rangelands are often used for multiple purposes such as wildlife production. The yield and nutritional value is less due, in part, to the inherent properties of the vegetation and the rangeland ecosystem such as forage species, topography, soil and environmental conditions, and previous use of the rangeland. In comparison to cultivated pasture forages, antinutritional factors are a more valid concern for rangeland forages. The specific antinutritional factor(s) varies across plant species and the concentration of the antinutritional factor varies with factors such as soil and environmental conditions. As a forage manager, it is important to know the potential species, the species’ antinutritional factors, factors influencing the concentration of the antinutritional factor, and to manage to reduce the opportunity for toxicity such as by providing adequate forage. In general, the economic losses are greater for decreases in production versus death of animals.

Management of the rangeland requires management of the interrelated factors of forage, animal, and rangeland systems. Management includes consideration for factors such as forage species, yield, nutritional value, and season available, appropriate stocking rate, distribution, and supplementation of animals, improvement of the resource, etc. Selection of animal species is dependent upon economic factors and range factors such as vegetation, water, topography, and predators. An effective management scheme may include common or dual use of the rangeland; the use of more than one species in the grazing system. As a result of the different preferences for forage species, portions of the forage, terrain, temperature, and distance from water between animal species, to achieve maximum forage utilization rangelands and cultivated pastures may be grazed by more than one species. Preferences for forage species vary with season and stage of maturity of the plant. In general, cattle are classified as nonselective grazers and prefer grasses and forage legumes. In contrast, sheep and goats are classified as selective grazers and will consume greater amounts of forbes and browse. To determine the appropriate extent of defoliation, the 50-50 rule is a good rule of thumb. According to the 50-50 rule, in the heavily grazed areas, graze 50% of the weight of the forage and leave 50% of the weight of the forage. Application of the rule will promote future forage production. The 50-50 rule can also be applied to cultivated pastures. Grazing according to season of use is also important for animal and future forage production. Season of use is determined by factors such as vegetation, topography, and climate. To describe season of use, rangelands are classified into spring-fall, winter, spring-fall-winter, and summer categories.

Improvement on rangelands is more complex than improvement on cultivated pastures. Indicators of rangeland degradation include a decrease in favorable forage species, an increase in unfavorable forage species, and an increase in erosion. Animal management practices to improve the rangeland include practices such as conservative stocking rates, appropriate seasonal use, and proper distribution of animals on the rangeland. Methods to improve animal distribution on the rangeland include use of a rotational system, use of fencing, herding, provision of additional water sources, appropriate location of supplemental feeds, controlling pests, and building trails to inaccessible portions of the rangeland. Additional rangeland improvement practices include reseeding and brush and weed control.

The principles of the grazing systems for rangelands are similar to the grazing systems for cultivated or seeded pastures. The following discussion will focus on a few of the features of range grazing systems. On ranges, the most common grazing system is the continuous grazing system. For a continuous system, grazing management is achieved via controlling stocking rate and animal distribution on the range. The advantages of a continuous grazing system are: 1) more efficient on less productive ranges; and 2) more practical for seasonal ranges. The disadvantages of a continuous grazing system are: 1) lower animal stocking rate; 2) lower animal production per unit area; 3) poorer animal distribution; and 4) less opportunity to use range improvement techniques. In general, forage and animal productivity are maximized, as well as the wildlife habitat and water resources are more effectively preserved, with a rotational system. For ranges, the two primary types of rotational grazing systems are deferred rotational and short duration grazing systems. For the deferred rotational systems, the season of grazing and resting periods for each pasture will vary from year to year.

Figure 8.16 illustrates a deferred rotational grazing system.

The figure also illustrates placement of supplement and water to improve animal distribution. Short duration rotational grazing systems involve frequent movement of animals between small pastures. The frequency of animal movement is dependent upon the availability of the forage; the more forage available, the more frequent the animal movement. Two short duration rotational grazing systems are the rectangular and the cell grazing systems.

Generally, the nutrients provided in the rangeland forage do not fulfill the nutrient requirements of the animal and therefore supplementation is required. The type and level of supplementation varies depending on the specific animal requirements and nutritional value of the forage. Supplementation will also vary by season and by year. In general, the nutrient(s) provided in a supplement are energy, protein, minerals (especially phosphorus), and vitamins (especially vitamin A). Energy supplementation may be required when the availability of forage is low, digestibility of the forage is low, opportunity for nitrate toxicity is high, or energy to protein ratio is low. In general, energy supplementation should be on a daily basis. In general, protein supplements are the largest supplement cost for producers. In addition to provision of protein, protein supplementation also improves utilization of additional nutrients. Protein supplementation can be provided every other day or twice per week. Additional feedstuffs may be added to the supplement to limit consumption. Typically, supplementation of macrominerals, microminerals, and vitamins is accomplished with the use of a carrier.

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