Sheep & Goat Research Journal. Volume 10, No. 1: 1994
Special Edition: The Role of Sheep Grazing in Natural Resource Management

Contents

The Role of Grazing Sheep in Sustainable Agriculture
Author: D.G. Ely
Multispecies Grazing: The Ecological Advantage
Author: J.W. Walker
Sheep Grazing and Riparian and Watershed Management
Author: H.A. Glimp and S.R. Swanson
Sheep Grazing as a Range Improvement Tool
Author: K.M. Havstad
Prescribed Sheep Grazing to Enhance Wildlife Habitat on North American Rangelands
Author: J.C. Mosley
Sheep Grazing as a Brush and Fine Fire Fuel Management Tool
Author: C.A. Taylor, Jr.
Sheep as a Sulvicultural Management Tool in Temperate Conifer Forest
Author: S.H. Sharrowy
Sheep: A Method for Controlling Rangelands Weeds
Author: B.E. Olson and J.R. Lacey
The Role of Sheep and Sheep Products in Waste Management
Author: J.S. Glenn

Article Summaries

The Role of Grazing Sheep in Sustainable Agriculture

Author: D.G. Ely
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Introduction

The world has challenged agriculture to continue to produce an abundance of food and fiber for an ever­ expanding population. The furor, developed over improving the global environment, dictates this production occur in a "clean" environment considered "safe" for all living organisms.

The United States has developed an efficient, highly productive food and fiber system envied by the world because consumers spend a lower percentage (11.8) of their income for food than any country in the world (Hess, 1991). However, the technology used in this development did not, in many cases, anticipate the potential social, environmental and health costs. An outcome of this magnificent progression is sustainable agricultural systems, which advocate the use of fewer exogenous materials, in smaller amounts, to maintain land productivity. Sustainable systems may require reduced grain feeding to animals an increased use of crop residue; and waste feed materials, reduced use of chemical fertilizers and greater reliance on legumes, reduced use of pesticides and herbicides, more extensive use of soil and water conservation measures and careful attention to water quality. This dichotomy, to produce more with Jess, points to the birth of significantly altered agricultural production systems in the future. One alteration will be a greater reliance on forages for food and fiber production. One animal which can contribute to feeding and clothing the world population in the future, because of its characteristic efficient use of forages in a sustainable environment, is the sheep.

Multispecies Grazing: The Ecological Advantage

Author: J.W. Walker
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Summary

Grazing of several species of herbivores on the same area typically results in more efficient utilization of forage resources and increases sustainable production. These benefits are the result of different dietary habits of the animals because plants avoided by one kind of livestock may be relished by another. Differences in dietary ha bits are related to the physical limitation on the ability to select and the physiological limitation on the ability to detoxify forage phytochemicals. Compared to cattle, sheep diets usually have more forbs and less grass. Sheep can graze lower in the forage canopy, have a greater ability to select from a fine-scale mixture and have a more varied diet than cattle. As available forage decreases, dietary overlap between sheep and cattle tends to decrease because cattle shift their diet to lower quality but mo.re available forage while sheep can continue to select their preferred diet. Averaged across a wide range of studies, multispecies grazing increased meat production by 24% compared to cattle-only grazing and by 9% compared to sheep-only grazing. This advantage is usually caused by both increased individual animal performance and increased carrying capacity. Despite the potential increases in economic and biological efficiency, multispecies grazing is not widely practiced. This valuable management practice should be promoted based on its ability to meet societal goals for more environ mentally sound agricultural production practices. Compared to single species grazing, multiple species of animals use vegetation resources more uniformly, which can enhance ecosystem stability.

Key words: sheep, cattle, goats, diet selection, diet overlap, foraging behavior, sustainable agriculture.

Sheep Grazing and Riparian and Watershed Management

Author: H.A. Glimp and S.R. Swanson
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Summary

This study was conducted to evaluate the reproductive performance of two-yr-old, sexually na?ve rams of different genotypes. Eight rams of each Awassi (A), F1 Charollais- Awassi (CA) and F1 Romanov-Awassi (RA) genotypes were subjected to sexual performance tests by being individually exposed to two estrous Awassi ewes for five, 20-min periods. Body weight (BW), body condition score (BCS), scrotal circumference (SC) and semen characteristics were recorded every 2 wk for 2 mo prior to sexual performance testing. Awassi rams engaged in more leg-kicking bouts (P < 0.01) than RA rams. Mounting frequency, raising the fat tail of females, and ejaculation rate were greater (P < 0.05) in A than in CA and RA rams. No genotype x test day interactions were detected, however, test day influenced (P = 0.05) ejaculation rate. Rams of the CA genotype had greater BW (P < 0.01) than RA and A. The CA rams had greater SC (P < 0.01) than A rams and higher BCS (P < 0.01) than RA rams. The RA rams had greater (P < 0.05) semen mass motility than A and lower (P < 0.05) percentage of abnormal spermatozoa than A and CA rams. Additionally, semen concentration tended (P < 0.10) to be greater in RA than in A and CA rams. Results of the present study indicate that RA rams tend to have better semen characteristics, while Awassi rams had better sexual performance when mated with fat-tailed females than the CA and RA genotypes, which may necessitate the use of artificial insemination during crossbreeding programs.

Sheep Grazing as a Range Improvement Tool

Author: K.M. Havstad
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Summary

Grazing is an integral and natural process on rangelands. Long-term studies have concluded that grazing can be managed to manipulate the vegetative composition of rangelands. There are two principle criteria that must be implemented to achieve improvement. First, grazing must be managed by established goals and realistic specific objectives. Without achievable goals and clearly stated objectives grazing would be unmanaged and extensive experiences have illustrated that unmanaged grazing by domestic and wild herbivores can result in catastrophe. Basic principles for establishing these goals and objectives are well documented. Second, improvement should be defined as attaining desired objectives for the rangeland resource. In some instances, improvement will equate with increased forage available for grazing livestock. In other instances, improvement will be based on non-livestock forage criteria. In all cases the resource will be benefitted and livestock will maintain an integral role in the renewable use and sustained management of rangelands.

Key words: rangelands, sheep, range improvement, grazing management.

Prescribed Sheep Grazing to Enhance Wildlife Habitat on North American Rangelands

Author: J.C. Mosley
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Abstract

Prescribed sheep grazing is a promising tool for enhancing all four wildlife habitat essentials: 1) food, 2) water, 3) cover, and 4) space. Sheep grazing is a low-cost, low-energy input form of habitat manipulation that can be implemented on a landscape scale for many wild life species' in diverse types of habitat. Through the manipulation of sheep foraging behavior, rangeland sheep grazing can purposely and favorably alter the yield, accessibility and nutritive quality of forage; the abundance of prey; the availability of water; the availability of thermal cover and security cover; and the amount of space available to wildlife. It is important to note, however, that these habitat alterations will only enhance a fauna's population if the limiting habitat factor is improved. Trade-offs must also be considered because it is impossible to maximize the habitat of all wildlife at once. Any alteration to one or more of the habitat essentials requisitely improves the habitat of some fauna yet simultaneously and inevitably degrades the habitat of others. Biological diversity of many terrestrial ecosystems can be improved by using prescribed sheep grazing to create diverse arrays of the four habitat essentials.

Sheep Grazing as a Brush and Fine Fire Fuel Management Tool

Author: C.A. Taylor, Jr.
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Summary

Rangelands throughout the U.S., as wet as the rest of the world, play a major role in supplying human populations with animal and plan t products, recreation and water and habitat for wildlife. A pivotal element in determining the actual use for any particular rangeland resource is the vegetation composition (i.e., the structure and species composition of range vegetation is the primary driving force in land use and management). A vegetation shift from grassland to woodland has been documented in most rangelands of the U.S. Increases of woody plants reduces livestock production potential, greatly alters wildlife habitat, reduces water availability to both rural and urban uses, increases soil erosion potential and can lower the overall recreational desirability of a region. Although there is not unanimous agreement, most authors have attributed this woody plant increase to grazing disturbance (heavy stocking), which reduced both fire frequencies and the removal of competition from grasses. Even though excessive livestock grazing has contributed to the increase of woody plants on rangeland, proper management based on a knowledge of the foraging process can be used to direct plant succession towards an improved range condition. Using sheep to manipulate vegetation appears to be an important part of the grazing management needed to reach this goal.

Key words: biological, brush management, fire, grazing, sheep.

Sheep as a Sulvicultural Management Tool in Temperate Conifer Forest

Author: S.H. Sharrow
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Summary

Sheep grazing is a traditional use of temperate coniferous forest in the United States and Canada. Like any management tool, prescription sheep grazing can be misused. Unacceptable damage to conifer regeneration can occur when sheep are poorly controlled or plantations are overgrazed. Relative attractiveness of trees compared to other forage available to sheep changes seasonally. Trees are most likely to be browsed during the spring when lush new twig and needle growth is present or any time that other green feed becomes scarce. Sheep browsing of young trees has relatively little impact upon conifer growth unless the terminal leader or almost all of current year's lateral branches are consumed. Properly applied sheep grazing often reduces competition between trees and other ground vegetation, thus increasing tree growth. Although prescriptions have yet to be fully determined for many forest sites, results to date suggest that prescription grazing may provide a socially acceptable alternative to herbicides for conifer release in many areas.

Key words: biological control, integrated pest management, brush livestock grazing, agroforestry.

Sheep: A Method for Controlling Rangelands Weeks

Author: B.E. Olson and J.R. Lacey
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Summary

Noxious rangeland weeds are difficult to control. Where the use of many control treatments are limited by environmental and economic constraints, sheep grazing is a potential weed control method. Sheep possess many traits that enable them to be used to control noxious weeds and reduce poisonous plant infestations. Currently, sheep arc used to control leafy spurge, spotted knapweed, tall larkspur, tansy ragwort and other weeds. In some cases, landowners assess renters a lower fee when their sheep graze weed-infested rangelands. Federal land management agencies often do not charge any fee when sheep grazing is used to control noxious weeds. The value of sheep as a weed control method, and subsequently their use on rangelands, is expected to increase in the future.

The Role of Sheep and Sheep Products in Waste Management

Author: J.S. Glenn
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Summary

Our appreciation of the potential role and value of sheep and their products in the handling of waste materials is still in its infancy. A limited number of novel applications are currently in use. However, with the increased interest in biological solutions to environmental problems, additional roles for sheep products will undoubtedly emerge. Key words: biological control, integrated pest management, brush livestock grazing, agroforestry.