E-34

Planned Considerations

No grazing system can compensate for overstock-ing. Animal numbers must be balanced with forageproduction. Therefore, light continuous grazing mayimprove range but cause lower returns per acre thananother system. Deferred rotation systems tend toallow the animals to graze more selectively than dothe heavy continuous or extensive short durationsystems. This results in increased animal perfor-mance and a slower rate of range improvement. Ex-tensive short duration systems favor greaterperennial plant growth. Depending upon rancherobjectives, a short duration system may be imple-mented to promote more rapid range improvement.Later, after the desired level of improvement isreached, a deferred rotation system or continuousgrazing at moderate stocking rate may be substitutedto maintain range condition and maximize livestockproduction.

The specific type of grazing system to choose willdepend upon many factors:1. The system must satisfy the rancher’s objectives

and meet the needs of livestock and/or wildlifeand the grazing resources. Also, the size ofrange, number of grazing units, climate, rangesites and range condition are important.

2. Physical facilities such as fencing, working pensand water storage should be considered in termsof forage use, livestock distribution andcosts/benefits. Increased numbers of livestockper pasture will require additional water supplies.

3. Special provisions for prolonged drought or other

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unusual circumstances should be included.Sufficient forage reserves to facilitate operationssuch as breeding, lambing, kidding or calvingmust be planned for. The numbers and kinds oflivestock in grazed pastures can vary to fit theforage and livestock needs.Rest periods should be long enough and at theproper season to accomplish specific manage-ment objectives for key forage species, but main-tain high forage quality for good livestocknutrition. Grazing period should be short enoughto provide adequate animal nutrition but notlong enough for animals to graze regrowth beforeplants recover.All domestic livestock must be removed frompastures being rested.

7. Numbers of wildlife animals should be controlledto prevent overuse of desired plants, providehigher quality diets and improve the animals’performance.

8. The grazing system should be started when thereis sufficient forage in the pastures(s) to be grazed.

9. The number of grazing animals and the amountof forage must be kept in balance. Herd sizeshould be flexible.

10. Grazing periods must be alternated during thegrowing season of the desired plants so that thesame units are not used at the same time eachyear.

11. Stock water must be provided in each grazing unitas needed for the number of stock and the periodof grazing expected.

12. Variations from a planned grazing system mayberequired to meet the needs of plants, livestock orwildlife. Necessary changes should reflect soundforage and livestock management. A system mustbe flexible.

13. Records of livestock and wildlife performance andpasture use and condition must be kept.

Kinds of Systems

Planned use refers to how, when and where theanimals are to be grazed. Planned use is based uponthe needs and characteristics of the ranchingenterprises and is designed to give maximum andefficient use of the forage over the entire ranch. Whendesigned and executed properly, a planned systemcan improve range and sustain maximum produc-tion. Adjustments may be necessary for a particularsystem to work in a particular livestock and wildlifeoperation. The rancher is responsible for the successor failure of a planned system. Each system must beflexible enough to adjust to current and expectedconditions as well as to changes in ranch objectives.

All systems are based on the main principle ofgrazing management - controlling the frequency andseverity of defoliation of individual plants. The im-mediate response of an individual plant to grazingmay be:1. increased plant vigor, as evidenced by increased

size or reproduction;2. decreased plant vigor or death; or3. neither a positive nor a negative reaction.

The major factor controlling the frequency andseverity of defoliation, regardless of the type of graz-ing system, is grazing pressure (defined as the animalunit, or forage demand, to forage supply ratio).Severity and frequency of defoliation will alwaysincrease as grazing pressure increases.

Under continuous grazing schemes stocked witha single class of livestock, grazing pressure can onlybe manipulated by stocking rate (the number ofanimals that a given area of range actually supportsfor a period of 12 months). This is also the case in thedeferred rotation systems. However, in these sys-tems a period of rest is periodically scheduled toensure that the grazed plants have an opportunity toregain their vigor. Under any short duration grazingsystem there is much greater control of the frequencyand severity of defoliation because the stocking rate,stocking density and length of graze/rest periodscan be manipulated to benefit plants or animals.

Continuous Grazing

Since the number of desirable forage species islimited on poor or fair ranges, it is difficult for themto reproduce under year-long grazing pressure, evenwith very light stocking rates. This is becauseanimals are selective grazers and will graze thepalatable species first. With year-long grazing thedesirable species are grazed continuously. On rangesin good condition, continuous grazing withmoderate stocking rates generally does not harmanimal or forage production. Animal production isoften more erratic under continuous grazing, butthissystem generally returns more income/acre thanmost other grazing systems.

Deferred Grazing

Removing grazinganimals for an adequate periodof time gives desirable plant species an opportunityto regain vigor and reproduce. Deferred grazing canbe of several types, any of which can be designed tomeet the requirements of both forage plants andgrazing animals.

Decision Deferment

Decision deferment is based on adapting the graz-ing system to specific needs or situations. The defer-ment usually is for the entire growing season, or fora part of it when moisture conditions are best. Suc-cess of this system depends upon the ability of themanager to make a correct decision. Decision defer-ment is recommended following range seedling andbrush control, or in situations where systematicdeferment cannot be applied economically.

Off an On

The off-and-on system is a method or rotatingdeferment based upon forage utilization. Theanimals are switched from one pasture to anotherwhen proper use of the key forage species has beenobtained. The duration of grazing is not specific be-cause the time required to obtain proper utilizationcan vary from year to year and from season to season.Also, the time of deferment is not specific because theanimals are not returned to a pasture until the keyforage species have regained their vigor and can begrazed without harm.

Systematic DefermentGrazing Programs

Four Pasture Deferred Rotation

This system was developed in 1949 by Dr. Leo B.Merrill at the Texas Agricultural Experiment Stationnear Sonora, and is known as the “Merrill” system.The four-pasture deferred rotation grazing programis rather simple in design (Fig.1). All four pasturesshould be about equal in grazing capacity. This isimportant because overgrazing will be detrimental

to the forage and cause the system to fail. The totalproper stocking rate of all four pastures is calculatedand stock are divided into three herds. Three pas-tures are then grazed while one is deferred. Thedeferment seasons should be based on climatic fac-tors, rainfall, growing season, nutritional needs ofthe livestock and requirements of the range plants.

Figure 1. It takes 4 years to complete the four-pasture deferred rotation grazing system.Each pasture is grazed 12 months then deferred for 4 months. There are three 16-monthgrazing cycles.

Pasture Deferred 1 Pasture Deferred 2July-October, first cycle November-February, first cycleNovember-February, second cycle March-June, second cycleMarch-June, third cycle July-October, third cycle

Pasture Deferred 3 Pasture Deferred 4March-June, first cycle March-June, first cycleJuly-October, second cycle July-October, second cycleNovember-February, third cycle November-February, third cycle

Two-Pasture Deferred Rotation

This system is sometimes called South AfricanSwitchback. The two-pasture system is generallysatisfactory, but may not give results as good as thefour-pasture deferred rotation system. However, thesystem is superior to year-long grazing.

Two pastures of nearly equal grazing capacity arenecessary. The total grazing capacity of both pas-tures is combined into one herd, so that the herd isrotated between the two pastures. The design of atwo-pasture system is given in Figure 2.

Figure 2. The two-pasture deferred rotation grazing system is completed in 2 years. Thereare 12-month grazing cycles with staggered grazing and deferment periods occurring inthe same year.

Pasture Deferred 1 Pasture Deferred 2June 16-November 15, first cycle March I5-June 15, first cycleNovember 16-February, second cycle June 16-November 15 second cycleMarch-June 15, third cycle November 16-February third cycle

The dates and periods of deferment should be selected for the specific area in which thesystem is to be used. The pasture being grazed should be observed often for signs ofexcessive overuse or deterioration.

Seasonal Grazing

Seasonal grazing is less common in the Southwestthan in the West and involves grazing in a specificseason only, such as spring, fall, summer or winter.Stocker operations may use a winter/spring grazingseason. This type is best used in the Southwest insituations involving both rangeland and tame pas-tures. The tame pastures should be grazed duringtheir most productive seasons, while the rangelandis deferred. Such a system can result in highly effi-cient livestock production at a low cost.

Short Duration Grazing

Short duration grazing (SDG) has relatively shorthistory in Texas. It is possible to improve range veryrapidly with long frequent rest periods. However,there may be reduced livestock production. There isa continuum in the deferment-grazing cycles of SDGthat ranges from short to long rests and short to longgrazing periods (Table 1). Extensive SDG is oftencalled “non-selective” grazing. The quality of the live-stock diet often declines after they have been in a