Grazing Management PDF
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PREFACE TO SECOND EDITION gnizarG tnemeganaM attempts to integrate the concepts, principles, and man- agement techniques that apply to all grazing lands and to all grazing animals. The kinds of grazing lands grazed by these ungulate herbivores range from native and seeded rangelands through several kinds of perennial pasture to temporary and crop aftermath pasture. An attempt has been made to cover big game herbivores with an intensity equivalent to domestic livestock, but only in some areas was this fully accomplished. Many academic disciplines for over half a century have focused attention on grazing management, and it is readily apparent that the subject must remain high- ly interdisciplinary. Although it seemed proper to compile a book about it, and now a second edition, the unknowns surrounding grazing management are readily ac- knowledged. It also is readily apparent that grazing management must remain dyn- mamic to accommodate and build upon new principles and applicatations as they become more fuly substantiated and documented. To accomodate the new infor- mation, concepts, and application during the past 10 years alone (since publica- tion of the first edition), this second edition has been increased in size and cover- age by about 50%. New insights into grazing management may require grazing managers and sci- entists to modify substantially their present as well as future concepts and prac- tices. New emphasis on grazing management in this second edition has included: (1) the role of post-ingestive feedback in diet selection, (2) spatial foraging deci- sions made by grazing animals, (3) the utility of the grazing animal as both an en- vironmental enhancement tool as well as a forage harvester and converter, and (4) an expansion of the concept of grazing as a natural ecosystem component. Recent research, evaluation, and use experience probably justify (5) the current XI X| I PREFACE TO SECOND EDITION trend away from a universal application of complex grazing systems while re- serving their use for special situations, (6) greater attention to differentiating be- tween complex grazing systems and simpler grazing methods and a greater appli- cation of the latter, and (7) a general return to the basics of grazing management. These new recent developments in grazing management have required (8) the fur- ther refinement of grazing management terminology and (9) the development of decision support systems to aid the grazing manager (the latter acknowledged but included only minimally in this second edition of gnizarG .)tnemeganaM The principles and practices emphasized in gnizarG tnemeganaM should apply throughout the world, even though social customs, agricultural policy, and land ownership may restrict their unlimited application. Even in North America cul- turN, social, and political philosophies and agendas continually invade and even detour the application of grazing management science and technology. A majori- ty of the examples of grazing management provided and much of the literature cited herein are of North American origin. Since grazing management is a rapid- ly developing science, extensive documentation seemed justified and has been pro- vided. Figure legends have also been utilized to summarize some of the salient points made in each chapter. gnizarG tnemeganaM is recommended both as a textbook and as a reference manual. As a textbook, its prime audience is expected to be university students in upper division and graduate levels with a major in range science, animal science, big game management, or agronomy. However, it should also serve as a compre- hensive reference manual for extension and research personnel, grazing land man- agers, innovative ranchers and farmers, agribusiness personnel, and conservation- ists generally. Although this book is not primarily designed as a field manual, the concepts and principles of grazing management have been tied to their application throughout. As this second edition of gnizarG tnemeganaM is a synthesis of the concepts, research data, and application experiences contributed directly and indirectly by many people, it is sincerely hoped that it will properly represent their conclusions. John E Vallentine Springfield, Utah 1 INTRODUCTION TO GRAZING I. The Role of Grazing Management A. Grazing Management Objectives B. Grazing Management Principles .C Grazing Management Decisions D. Terminology of Forages II. Kinds of Grazing Lands A. Long-Term Grazing Lands B. Medium-Term Grazing Lands .C Short-Term Grazing Lands (Cropland Pasture) III. Grazing Management Applications A. Management Intensity and Flexibility B. Pastoral Systems .C Range .sv Pasture .VI Grazing as an Ecosystem Component A. Plant Evolution under Herbivory B. Sustainability of Livestock Grazing .C The Ecology of Grazing Discontinuation D. Climax as an Objective .V The Importance of Grazing VI. Grazing and Land Use Planning .1 THE ROLE OF GRAZING MANAGEMENT A. GRAZING MANAGEMENT OBJECTIVES Grazing management is the manipulation of animal grazing to achieve de- sired results based on animal, plant, land, or economic responses, but the contin- uing immediate goal is to supply the quantity and quality of forage needed by the grazing animal for it to achieve the production function intended. Grazing man- agement is important because this is where theory is put into practice (Walker, 1995). The grazier is the person who manages the grazing animals, i.e., the graz- ers (including browsers). These terms have a common stem in the verb graze, 2 1 INTRODUCTION TO GRAZING which specifies the consumption of standing forage by ungulate herbivores. Graz- ing of standing forage on range and pasture is the counterpart of mechanical (ma- chine) harvesting of harvested forage crops (Fig. 1.1), except that the grazing an- imal is both the consumer and the converter, as well as the harvester, of grazed forage. Ranch management is the manipulation of all ranch resources--including not only the grazing resources but also all the financial, personnel, and physical resources of the ranch--to accomplish the specific management objectives set for the ranch. In this regard, grazing management is only one aspect, albeit a very im- portant one, of total ranch management. Where animal grazing is a prominent component of a farm operation and involves substantial use of lands for grazing, grazing management will necessarily play a similar role in farm management. Em- phasis on grazing management is well deserved on both farm and ranch because of its relatively low cost and potentially great returns per unit of management in- put (Lewis and Volesky, 1988). Grazing land management--which principally integrates both range and pas- ture management--is the art and science of planning and directing the develop- ment, maintenance, and use of grazing lands to obtain optimum, sustained returns based on management objectives. The effective grazing planner/manager must in- ventory all sources of available grazing capacity and integrate them into the best animal production system. The management interrelationships of different kinds of grazing lands, when used in a single production system, are great and must not be overlooked or ignored. The use of rangeland is generally comingled with the use of other types of graz- ing land, and most range livestock and many big game animals use multiple sources of grazing capacity to meet their annual requirements (Vallentine, 1978). Grazing management is also a major component in the multiple-use management of public lands, whether the grazing is by domestic livestock or big game animals or a combination of both. The positive manipulation of the soil-forage plant-grazing animal complex is a noitcudorP gnitsevraH serovibreH dezarG egarof gnizarG LIq noitcudorp ~ tnemeganam "~ I segaroF 1~ I I L laminA noitcudorp I ,elttac( ,peehs ,staog / ,sesroh gib )emag tsevraH egarof lacinahceM noitcudorp gnitsevrah FIG U R E .1 I ehT laud gnitsevrah-noitcudorp seuneva of egarof noisrevnoc yb .serovibreh THE ROLE OF GRAZING MANAGEMENT 3 central role of the grazing manager. Opportunities to enhance the energy efficien- cy of the soil-forage-ruminant complex exist in three principal areas: .1 Increase conversion of radiant solar energy to usable form through photo- synthesis during growth of the forage plants, i.e., by enhancing the quanti- ty and quality of forage produced on the site. 2. Increase consumption of the energy fixed by forage plants by the grazing animal (i.e., livestock or big game) through optimal management of graz- ing and reducing forage waste and nonproductive consumption. 3. Increase conversion of the ingested energy by the grazing animal into products directly usable by humans through improved animal genetics, nutrition, and health. Savory (1987) has recognized two additional links for completing the grazing resource management and economics chain: (1) the market link, involving the ac- tive marketing of the "packaged product" and conversion into "solar" dollars of new wealth; and (2) the reinvest link, involving the return of "solar" dollars through reinvestment to strengthen the chain at its weakest link in a constant growth/stability process. B. GRAZING MANAGEMENT PRINCIPLES Managing and manipulating the grazing animal-forage plant-soil complex to obtain specific objectives are accomplished by blending ecological, economic, and animal management requirements. The principles of grazing management remain the same regardless of the kind of grazing land: (1) optimal stocking rate (i.e., num- ber of animals), (2) optimal season(s) of use (i.e., timing of grazing), (3) optimal kind or mix of large herbivore species, and (4) optimal grazing distribution. Never- theless, their application and the relative emphasis on cultural treatments may vary considerably depending upon the kind of grazing land, the management objectives, and the economic implications. And, finally, after these four principles have been made operative, it is appropriate to select and implement special management tech- niques referred to as grazing methods and grazing systems (Hart et al., 1993). Common to the management of all grazing lands must be forage plant consid- erations such as plant growth requirements, providing for plant vigor and repro- duction, defoliation and other animal impacts, seasonality and fluctuations in for- age production, and ecological status of the plants. But equally high in priority are animal considerations including animal performance, animal behavior, nutrient re- quirements and intake levels, forage quality relative to specific animal needs, and forage palatability and animal preference. Opportunities exist to manipulate the forage resource to better fit the specific kind or class of grazing animal. Still an- other approach is the manipulation of the grazing animal (species of animal, stage of production, and calendar events in the animal production cycle) to better fit the forage resource, or an even better alternative will generally be the integration and simultaneous application of both approaches. 4 1 INTRODUCTION TO GRAZING • Heady (1974) has listed nine ways in which the grazing animal influences its habitat: (1) intensity of defoliation, (2) frequency of defoliation, (3) selectivity of defoliation, (4) seasonality of defoliation, (5) distribution of animals, (6) distribu- tion of plants, (7) distribution of minerals, (8) physical effects, and (9) cycling of minerals. Each of these factors, in turn, affects the productivity and welfare of the grazing animal. Grazing management has the challenge of recognizing and bene- ficially enhancing the positive impacts of these factors or reducing any negative impacts on the plant-animal-soil complex. These factors will receive detailed attention in subsequent chapters. C. GRAZING MANAGEMENT DECISIONS Grazing management, since it is both a science and an art, should be based on both the knowledge of science and the wisdom of practical experience and appli- cation. Because of the intricacies and variability of the animal-forage-land bio- logical system, the management of grazing animals on grazing lands may require as much art as science to make continual adjustments as needed. The concept of grazing management implies decision making (Fig. 1.2). Profitable decision mak- ing requires knowledge about forage plant species, animal responses desired rel- ative to the market, and the forage plant-animal-land interactions (Matches and Bums, 1985). FIG 2 E R . U 1 Grazing tnemeganam noisiced seriuqer gnikam no desab htob eht egdelwonk of ecneics dna modsiw eht of lacitcarp .ecneirepxe ytisrevmU( of ).otohp anozirA THE ROLE OF GRAZING MANAGEMENT 5 The grazing land manager is frequently called upon to solve complex plant- animal problems associated with the management of grazed ecosystems, and the rancher additionally must meet the challenge of adding financial and personnel re- sources into the solution. "Decision support systems (DSS)... bring an integrat- ed approach to bear on complex problems .... Decision support systems can en- compass methodologies as diverse as hard-core computer models, expert systems, geographic information systems, discussion groups, and (even) structured thought processes" (Stuth and Smith, 1993). DSS can appear as computer programs but also on paper or videos or can emanate from human beings themselves in speech or writing. Of the numerous computer models now being used or developed as decision support systems, only two are mentioned here: (1) the Grazingland Alternative Analysis Tool (GAAT) and the Grazing Lands Application (GLA). GAAT was de- veloped at Texas A&M University to estimate the economic efficiency of a wide range of grazing land production systems. Systems that can be analyzed, either in- dividually or in combination, include livestock, wildlife, leased grazing, grain and forage crops, nonforage crops, and even investment in grazing land development (Kreuter et al., 1996). GLA is a computer planning tool for use on grazing lands that is based on an initial model developed by Texas A&M and is now used by USDA's Natural Resources Conservation Service in ranch and farm planning (Stine, 1998). Nevertheless, there are caveats that must be considered in using computerized decision support systems to make grazing management and related decisions. Computerized grazing models must include not only a biological but also a man- agerial counterpart (Christian, 1981). Grazing lands cannot be managed by com- puters alone; qualified, trained individuals make good grazing management deci- sions (Rittenhouse, 1984). Until the data pool on the focal subject becomes large enough to provide reliable numbers for computer input, a reasoned expert opinion may be more appropriate for many difficult management choices. A precise num- ber with insufficient or inadequate formulation is seldom better than an informed guess and may be even less reliable (Van Dyne et al., 1984a). Limitations of computer support systems have been pointed out by Stuth and Smith (1993): "Some decisions are clearly too trivial for DSS; others have so many sources of uncertainty that it is probably safer to leave them to the integrative pow- ers of the human brain rather than give results an unwarranted aura of reliability." While there are circumstances where personal decisions are likely to operate more reliably than decisions by computer, some decisions are technologically inappro- priate for answering by computer. Nevertheless, current computerized DSS repre- sent a major breakthrough in providing a useful tool to aid in making grazing man- agement decisions. Effective grazing management requires a comprehensive plan to secure the best feasible use of the forage resources. Such a plan must provide for the daily, sea- sonal, and annual grazing capacity needs of the livestock and/or big game; it must also seek to match the quantity and quality of grazing animal unit months (AUMs) 6 1 INTRODUCTION TO GRAZING produced on the ranch or grazing land unit with the AUM needs of the grazing an- imals associated with it. However, grazing management is much more complex than even this; the grazing management plan and subsequent operational decisions must include a wide variety of economic, managerial, and biological considera- tions along with their many interactions. The objectives of the grazing plan should include long-term stability as well as immediate profitability or other economic criteria of production (Morley, 1981). The planning time frame for individual grazing land units must be as long as the projected life of the forage stand, commonly a few weeks to several months for annual pasture, 25-50 years for some perennial pastures, or of unlimited contin- uation for native and seeded rangelands. For the longer term grazing lands, man- agement including stand maintenance must provide for a continuation of desired forage and animal production on a sustained yield basis. D. TERMINOLOGY OF FORAGES The terminology related to forages and other feedstuffs available for animal consumption must be consistently used. The following are suggested: Feed. Any noninjurious, edible material, including forage, having nutritive value for animals when ingested; synonym, feedstuff. Forage. Edible (i.e., acceptable for animal consumption) parts of plants, oth- er than separated grain, that can be consumed by grazing animals or me- chanically harvested for feeding; includes the edible portion of herbage, also browse and mast. Herbage. The biomass of herbaceous plants, generally above ground but may be specified to include edible roots and tubers; generally includes some plant material not edible or accessible to ungulate herbivores. Browse. Leaf and twig growth of shrubs, woody vines, and trees acceptable (edible) for animal consumption. Mast. Fruits and seed of shrubs, woody vines, trees, cacti, and other non- herbaceous plants acceptable (edible) for animal consumption. Grazed forage. Forage consumed directly by the grazing animal from the standing crop; synonym, pasturage. Harvested forage. Forage mechanically harvested before being fed to ani- mals in the form of hay, haylage, fodder, stover, silage, green chop, etc. Forage crop. A crop consisting entirely or mostly of cultivated plants or plant parts produced to be grazed (grazed forage) or mechanically har- vested for use as feed for animals (harvested forage). Roughage. Plant materials and other feedstuffs high in crude fiber (20% or more) and low in total digestible nutrients (TDN) (60% or less), usually bulky and coarse; synonymous with forage only in part. Concentrate feed. Grains or their products or other processed feeds that con- tain a high proportion of nutrients (over 60% TDN) relative to bulk and are low in crude fiber (under about 20%). KINDS OF GRAZING LANDS 7 .1I KINDS OF GRAZING LANDS Grazing lands include all lands vegetated by plants, either native or intro- duced, which are grazed or have the potential to be grazed by animals. An array of kinds of grazing lands results from a continuum of soil/site factors, vegetation/ forage stands, and management projections and applications. Use of the terms wild, tame, artificial, synthetic, and natural when applied to grazing lands is unreliable in projecting site adaptation, longevity, and even usefulness of forage plant species and the combinations or variety of forage stands they comprise. The development of improved cultivars of both native and introduced species seems to make such terms nearly redundant. Except where required for correlation of concepts, such terms have been avoided in this pub- lication. The terms "improved" and "unimproved," when applied to grazing land, can also be misleading unless precisely defined or described and consis- tently used thereafter. The case against using annual and perennial to describe grazing lands may also be misleading; annual forage species may be capable of reseeding themselves for a few years, and perennials can variously be used for a single year, limited to a specified number of years, or managed for unlimited continuation. The following classification (outlined in Fig. 1.3) has the objective of describ- ing and correlating the major categories of grazing lands for use in their planning and management. It arranges all grazing lands into broad categories by blending ecological site factors with intended land use and management objectives (Val- lentine, 1988). Since grazing lands differ greatly in the following characteristics, these have been used as the principal basis of classification: (1) projected grazing use longevity, (2) climax orientation of the vegetation and its management, (3) ara- bility of the land, (4) land capability and potential productivity, and (5) relative emphasis on cultural treatments. However, boundaries between the categories as discussed are artificially abrupt rather than being naturally gradual and transition- T T ! I .I Long-term grazing lands .A Native range ,> .B Seeded range (native )seiceps > ~ ,> E .C Seeded range decudortm( )setceps o -e ,-, ::I .II Medium-term grazing lands ~ )1(= "-- ~ ~' o ~ )1I .A Transitory erutsap / range .B Permanent pasture ~ ~ .III mret-trohS gnizarg sdnal 9.( ~ 1 .A noitator-porC erutsap I I .B yraropmeT erutsap .C porC eudiser/htamretfa erutsap FIGURE 1.3 Classification of grazing lands (arrows indicate increasing levels of emphasis). 8 1 INTRODUCTION TO GRAZING . al, additional local adaptation may be required, and the kind of grazing land may be altered over time. A. LONG-TERM GRAZING LANDS Long-term grazing lands (synonym range) are mostly nonarable lands on which the present forage stand is projected for unlimited continuation. Ecological principles provide the management basis, but grazing manipulation and cultural treatment inputs may be used to manipulate the forage stand. Cultural treatments may be limited by low site potential and/or cost-benefit considerations but are not excluded. Grazing management levels may vary from extensive to intermediate, but fencing and stockwater developments are generally given high priority. Long- term grazing lands, often environmentally severe, consist primarily of land capa- bility classes 1 IV through VIII but are not limited thereto (Fig. 1.4). 1. Native Range Native range consists of natural vegetation of predominantly grasses, grasslike plants, forbs, and shrubs; tree overstory may be present or absent. Climax vegetation or a high seral stage is often the objective of management. No substantive artificial re- seeding has occurred in the past, and useful, introduced species are minimal. Mainte- nance treatments will be provided when urgent but are currently planned as minimal. 2. Seeded Range (Native Species) Seeded range (native species) has been treated to enhance or reestablish the nat- ural vegetation by reseeding local strains or new cultivars of native species. Such grazing lands may include interseedings and/or marginal cropland or reclamation sites restored to long-term grazing. Minimal future cultural treatment is projected. 3. Seeded Range (Introduced Species) Seeded range (introduced species) has been fully or partially converted by seed- ing to long-lived, adapted, introduced species. Such grazing lands may include in- terseedings and/or marginal cropland or reclamation sites restored to long-term grazing. The duration of the newly established stand under grazing is projected to exceed 50 years. Minimum to moderate maintenance treatment is projected, but some treatment may be required periodically to prevent natural succession. B. MEDIUM-TERM GRAZING LANDS These include both arable and nonarable lands on which the projected long- term grazing tenure is extended but uncertain. The levels of past and projected fu- ture cultural treatment are highly variable, depending upon site potential and own- ILand capability classes I through IV are suited to cultivation, with I having few limitations and IV the most. Classes V through VIII are not suited to cultivation. Classes V through VII are generally suit- ed to livestock but VIII only to minimal wildlife use (Klingebiel and Montgomery, 1961).
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