Grazing

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"Graze" redirects here. For the Live song, see Secret Samadhi.
Red Kangaroo grazing
A Masaai herdsman grazing his cattle inside the Ngorongoro crater

Grazing has two distinct meanings. First, grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae. Many small selective herbivores follow larger grazers, who skim off the highest, tough growth of plants, exposing tender shoots. For terrestrial animals, grazing is normally distinguished from browsing in that grazing is eating grass or forbs, and browsing is eating woody twigs and leaves from trees and shrubs.[1] Grazing differs from true predation because the organism being grazed upon is not generally killed. Grazing differs from parasitism as the two organisms do not live together, nor is the grazer necessarily so limited in what it can eat (see generalist and specialist species). Water animals that feed for example on algae found on stones are called grazers-scrapers. Grazers-scrapers feed also on microorganisms and dead organic matter on various substrates.[2]

Second, grazing is a method of agriculture in which domestic livestock are used to convert grass and other forage into meat, milk and other products.

In animal behaviour[edit]

Green sea turtle grazing seagrass.

Grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae.

In zoology, "graminivory" is a form of grazing. A graminivore is an herbivorous animal that feeds primarily on grass[3] (specifically "true" grasses; plants of the family Poaceae). The word is derived from Latin graminis, meaning "grass", and vorare, meaning "to eat." Horses, cattle, capybara, hippopotamuses, grasshoppers, geese, and giant pandas are examples of graminivores. Some carnivores, such as dogs and cats, are known to eat grass occasionally.

Giant panda[edit]

Giant pandas (Ailuropoda melanoleuca) have evolved to be obligate bamboo grazers, and 99% of their diet consists of sub-alpine bamboo species.[4]

Rabbit[edit]

Rabbits are herbivores that feed by grazing on grass, forbs, and leafy weeds. They graze heavily and rapidly for about the first half hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding. If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours, grazing at intervals. Their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem by using a form of hindgut fermentation. They pass two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are immediately eaten (a behaviour known as coprophagy). Rabbits reingest their own droppings (rather than chewing the cud as do cows and many other grazer) to digest their food further and extract sufficient nutrients.[5]

Capybara[edit]

Grazing capybara

Capybara are herbivores that graze mainly on grasses and aquatic plants,[6][7] as well as fruit and tree bark.[8] As with other grazers, they can be very selective[9] and will feed on the leaves of one species and disregard other species surrounding it. They eat a greater variety of plants during the dry season, as fewer plants are available. While they eat grass during the wet season, they have to switch to more abundant reeds during the dry season.[10] The capybara's jaw hinge is not perpendicular and therefore they chew food by grinding back-and-forth rather than side-to-side.[11] Capybara are coprophagous, as a source of bacterial gut flora, to help digest the cellulose in the grass that forms their normal diet, and to extract the maximum protein and vitamins from their food. They may also regurgitate food to masticate again, similar to cud-chewing by a cow.[12] As with other rodents, the front teeth of capybara grow continually to compensate for the constant wear from eating grasses;[13] their cheek teeth also grow continuously.[11]

Hippopotamus[edit]

The hippopotamus is a large, semia-quatic, mammal inhabiting rivers, lakes and mangrove swamps. During the day, they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grasses. While hippopotamuses rest near each other in the water, grazing is a solitary activity. Their incisors can be as long as 40 cm and the canines up to 50 cm,[14] however, the canines and incisors are used for combat and play no role in feeding. Hippos rely on their broad, horny lips to grasp and pull grasses which are then ground by the molars.[15] The hippo is considered to be a pseudoruminant, it has a complex three- or four-chambered stomach but does not "chew cud".[16]

Non-grass grazing[edit]

Although grazing is typically associated with mammals feeding on grasslands, or more specifically livestock in a pasture, ecologists sometimes use the word in a broader sense, to include any organism that feeds on any other species without ending the life of the prey organism.[17]

Use of the term varies even more than this, for example a marine biologist may describe herbivorous sea urchins that feed on kelp as grazers, even when they kill the organism by cutting the plant at the base. Malacologists sometimes will apply the word to aquatic snails that feed by consuming the microscopic film of algae, diatoms and detritus, a biofilm, that covers the substrate and other surfaces underwater.

In agriculture[edit]

History[edit]

United States[edit]

Sheep grazing on public (BLM) land, Snake Valley, Utah

The use of livestock grazing can be dated back to the Civil War. During this time, land ownership was not common, and ranchers grazed their cattle on the surrounding, often federal, land. Not having a permanent home, these cowboys would frequently graze an area down, and then continue on their way. More commonly, however, cattle were rotated between summer and winter ranges. Soon, the public saw how profitable cattle could be and many tried to get into the cattle business. With the appearance of free, unlimited grass and feed, the land became overcrowded and the forage rapidly depleted. Ranchers tried to put a stop to this by using barbed wire fences to barricade their land, water sources, and cattle. After failed attempts, the Taylor Grazing Act was enacted in 1934. This act was put into place to help regulate the use of public land for grazing purposes and allotted ranchers certain paddocks of land. Additionally, “fees collected for grazing livestock on public lands was returned to the appropriate grazing district to be used for range improvements”.[18] The Taylor Grazing Act helped to stabilize rancher’s operations and allow them to continue raising their livestock.

Grazing systems[edit]

In the 19th century, grazing techniques were virtually non-existent. Pastures would be grazed for long periods of time, with no rest in between. This led to overgrazing and it was detrimental to the land, wildlife, and livestock producers. Today, ranchers have developed grazing systems to help improve the forage production for livestock, while still being beneficial to the land.

Seasonal[edit]

Free range grazing, goats in the Philippines

Seasonal grazing incorporates “grazing animals on a particular area for only part of the year”.[19] This allows the land that is not being grazed to rest and allow for new forage to grow.

Rotational[edit]

Rotational grazing “involves dividing the range into several pastures and then grazing each in sequence throughout the grazing period”.[19] Utilizing rotational grazing can improve livestock distribution while incorporating rest period for new forage.

Rest rotation[edit]

Rest rotation grazing "divides the range into at least four pastures. One pasture remains rested throughout the year and grazing is rotated amongst the residual pastures."[19] This grazing system can be especially beneficial when using sensitive grass that requires time for rest and regrowth.

Deferred rotation[edit]

Deferred rotation “involves at least two pastures with one not grazed until after seed-set”.[19] By using deferred rotation, grasses can achieve maximum growth during the period when no grazing occurs.

Patch-burn grazing[edit]

Patch-burn grazing burns a third of a pasture each year, no matter the size of the pasture. This burned patch attracts the grazers (cattle or bison) which graze the area heavily because of the fresh grasses that grow in. The other patches receive little to no grazing. During the next two years the next two patches burn consecutively and then the cycle begins anew. In this way, patches receive two years of rest and recovery from the heavy grazing. All this results in a diversity of habitats that different prairie plants and birds can utilize, mimicking the effects of the pre-historical bison/fire relationship where bison heavily graze one area and other areas have opportunity to rest.[20]

The Tallgrass Prairie Preserve in Northeast Oklahoma is within the Flint Hills ecosystem, and they have been patch-burn grazing with bison herds for over ten years now. Their efforts have effectively restored the bison/fire relationship on a large landscape scale of 30,000 acres (12,000 ha).[21]

Riparian area grazing management[edit]

Riparian area grazing is used more towards improving wildlife and their habitats. It uses fencing to keep livestock off ranges near streams or water areas until after wildlife or waterfowl periods, or limiting the amount of grazing to a short period of time.

Ecological effects[edit]

Old Norwegian Sheep grazing at an island on the coast of Norway. This is a vulnerable habitat where the sheep take part in a delicate ecological balance.

A number of ecological effects derive from grazing, and these may be either positive or negative. Negative effects of grazing (or more usually over-grazing) include increased soil erosion, adverse water quality impacts from increased runoff and loss of biodiversity. For example historical grazing, along with other land conversion, in Northern and Central California has reduced native chaparral and forest lands by approximately 70 percent. Ongoing grazing expansion {and land conversion} driven by human population growth in this region threatens the remaining integrity of California chaparral and woodlands habitat in this region.[22]

In some habitats, appropriate levels of grazing may be effective in restoring or maintaining native grass and herb diversity in rangeland that has been disturbed by overgrazing, lack of grazing (such as by the removal of wild grazing animals), or by other human disturbance. Conservation grazing is the use of domestic livestock to manage such habitats, often to replicate the ecological effects of the wild relatives of livestock, or those of other species now absent or extinct. For example, heathland in Europe requires grazing by cattle, sheep or other grazers to maintain its structure and diversity.

Much grazing land has resulted from a process of clearance or drainage of other habitats such as woodland or wetland.[23]

Benefits[edit]

Production[edit]

By utilizing grazing systems, livestock production has the potential to be maximized. “Approximately 85 percent of U.S. grazing lands are unsuitable for producing crops. Grazing animals on this land more than doubles the area that can be used to produce food. Cattle serve a valuable role in the ecosystem by converting the forages humans cannot consume into a nutrient-dense food”.[24] Some[who?] could say ranchers themselves are conservationists. They work to use natural resources and often perform tests on their land to analyze soils, control weeds, and utilize smart grazing practices. Through this, they benefit themselves by using profitable land to maximize their livestock production in turn for a profit.

Environmental[edit]

Grazing is beneficial to the ecosystem. It is advantageous towards the soil and grasses, promoting nutrient dense soil and stimulating the growth of plant varieties. Through grazing, livestock encourages plant growth, consequently increasing forage production. Furthermore, the animal’s urine and feces "recycle nitrogen, phosphorus, potassium and other plant nutrients and return them to the soil".[25] It also acts as rations for insects and organisms found within the soil. These organisms “aid in carbon sequestration and water filtration”.[25] Nutrients and organisms, all of which are necessary for soil to be prosperous and capable for production.

Grazing also helps to promote the growth of native plants and grasses. Often, these indigenous plants are not able to compete with the surrounding plants that utilize the majority of water and nutrients. By livestock grazing, the non-native grasses are controlled and the native plants can redevelop. As well as using grazing to increase plant growth, the actual hoof action of the livestock also promotes growth. The trampling helps to imbed the seeds into the soil so that the plants and grasses can continue to germinate. Additionally, management in many parks makes use of grazing to help lower fire hazards by reducing the amount of potential fuel, such as large buildups of forage. When the land is not grazed, dead grasses accumulate. These dead grasses are often a large fire hazard in the summer months. On the other hand, grazing can also allow for "accumulation of litter (horizontal residue)"[26] helping to eliminate soil erosion. Soil erosion is important to minimize because with the soil erosion comes a loss of nutrients and the topsoil. All of which are important in the regrowth of vegetation.

Biodiversity[edit]

Grazing may also promote biodiversity. Many species are dependent on ranch lands and grazing animals to maintain their habitat. The grasses that are stimulated through grazing provide a habitat for many species. When the land is left unattended or is not grazed, grasses will die with the seasons and accumulate as litter on the ground. For many birds, this is not attractive and they avoid making a nesting area of it. However, when the grass is grazed, the dead litter grass is reduced and allows for the birds to utilize it, while at the same time the livestock benefit.[27] Just as importantly, it increases species richness. When grazing is not used, many of the same grasses grow, for example, brome and bluegrass, consequently creating a monoculture.

In North American tallgrass prairies, diversity and productivity are controlled to a large extent by nitrogen availability…Nitrogen availability in prairies was driven by interactions between frequency of fires and grazing by large herbivores…Spring fires enhance growth of certain grasses, and herbivores such as bison preferentially graze these grasses, keeping a system of checks and balances working properly, and allowing many plant species to flourish.[28]

Grazing management[edit]

It is apparent that appropriate landuse and grazing management techniques need to balance maintaining forage and livestock production, while still maintaining biodiversity and ecosystem services.[29][30] Through the utilization of grazing systems and making sure to allow proper recovery periods for regrowth, both the livestock and ecosystem will benefit. Along with recovery periods, producers can keep a low density on a pasture, so as not to overgraze. Controlled burning of the land can be valuable in the regrowth of indigenous plants, and new lush growth. Additionally, producers can increase plant and species richness through grazing, by providing an adequate habitat. Although grazing can be problematic for the ecosystem at times, it is clear that well-managed grazing techniques can reverse damage and improve the land.

England and Wales[edit]

On most commons in England and Wales, rights of pasture and pannage for each commoner are tightly defined by number and type of animal, and by the time of year when certain rights could be exercised. For example the occupier of a particular cottage might be allowed to graze fifteen cattle, four horses, ponies or donkeys, and fifty geese, whilst the numbers allowed for their neighbours would probably be different. On some commons (such as the New Forest and adjoining commons), the rights are not limited by numbers, and instead a marking fee is paid each year for each animal turned out.[31] However, if excessive use was made of the common, for example, in overgrazing, a common would be stinted,[32] that is, a limit would be put on the number of animals each commoner was allowed to graze. These regulations were responsive to demographic and economic pressure. Thus rather than let a common become degraded, access was restricted even further.

See also[edit]

References[edit]

  1. ^ "Browsing is a specialized form of grazing. "Graze, verb: 2. Eat growing grass." "Browse, verb: 1. Feed on, crop, (leaves, twigs, scanty vegetation)."". Concise Oxford Dictionary (6 ed.). 1976. ISBN 0-19-861122-6. 
  2. ^ Begon M., Townsend C. and Harper J. (1990). Ecology (2 ed.). Blackwell Science, London. ISBN 0-86542-111-0. 
  3. ^ Graminivorous - Definition and More from the Free Merriam-Webster Dictionary
  4. ^ ZHOU, Shiqiang, et al. (2012). "Effects of wildness training giant pandas? Grazing and artificial harvesting on clone population biomass of umbrella bamboo (Fargesia robusta)". Chinese Journal of Applied & Environmental Biology 18 (1): 1–8. 
  5. ^ "Information for Rabbit Owners — Oak Tree Veterinary Centre". Oaktreevet.co.uk. Retrieved 2010-08-30. 
  6. ^ Capybara Facts. Smithsonian National Zoological Park. Retrieved on December 16, 2007.
  7. ^ Forero-Montana J, Betancur J and Cavelier J (2003). "Dieta del capibara Hydrochaeris hydrochaeris (cavia: Hydrochaeridae) en Caño Limón, Arauca, Colombia". Rev. Biol. Trop 51 (2): 571–578. PMID 15162749.  PDF
  8. ^ Capybara. Palm Beach Zoo. Retrieved on December 17, 2007.
  9. ^ Quintana, R.D., S. Monge, A.I. Malvárez (1998). "Feeding patterns of capybara Hydrochaeris hypdrochaeris (Rodentia, Hydrochaeridae) and cattle in the non-insular area of the Lower Delta of the Parana River, Argentina". Mammalia 62 (1): 37–52. doi:10.1515/mamm.1998.62.1.37. 
  10. ^ Barreto, Guillermo R.; Herrera, Emilio A. (1998). "Foraging patterns of capybaras in a seasonally flooded savanna of Venezuela". Journal of Tropical Ecology 14: 87. doi:10.1017/S0266467498000078. JSTOR 2559868. 
  11. ^ a b Capybara. Hydrochaeris hydrochaeris. San Francisco Zoo
  12. ^ Lord-Rexford, D. (1994). "A descriptive account of capybara behaviour". Studies on neotropical fauna and environment 29 (1): 11–22. doi:10.1080/01650529409360912. 
  13. ^ Bristol Zoo Gardens (UK) ''Capybara''. Bristolzoo.org.uk. Retrieved on 2011-12-07.
  14. ^ Estes, R. (1992). The Behavior Guide to African Mammals: Including Hoofed Mammals, Carnivores, Primates. University of California Press. pp. 222–26. ISBN 0-520-08085-8. 
  15. ^ Kingdon, J. (1988). East African Mammals: An Atlas of Evolution in Africa, Volume 3, Part B: Large Mammals. University Of Chicago Press. pp. 256–77. ISBN 0-226-43722-1. 
  16. ^ Eltringham, S.K. (1999). The Hippos. Poyser Natural History Series. Academic Press. ISBN 0-85661-131-X. 
  17. ^ Begon, M., Townsend, C. and Harper, J. (1996). Ecology (3 ed.). Blackwell Science, London. 
  18. ^ "History of Public Land Livestock Grazing". Retrieved 1 Dec 2008
  19. ^ a b c d "Grazing Systems". Grasslands Conservation Council of British Columbia. Retrieved 1 Dec 2008[dead link]
  20. ^ Fuhlendorf, S. D.; Engle, D. M. (2004). "Application of the fire–grazing interaction to restore a shifting mosaic on tallgrass prairie". Journal of Applied Ecology 41 (4): 604–614. doi:10.1111/j.0021-8901.2004.00937.x. 
  21. ^ The Nature Conservancy. (2010). Oklahoma: Tallgrass Prairie Preserve. Retrieved from http://www.nature.org/wherewework/northamerica/states/oklahoma/preserves/tallgrass.html
  22. ^ C.Michael Hogan (2008) Aesculus californica, Globaltwitcher.com, ed. N. Stromberg
  23. ^ (1999) A. Crofts and R.G. Jefferson eds. (1999) Lowland Grassland Management Handbook, chapter 2
  24. ^ "Fact Sheet: The Environment and Cattle Production". Cattlemen's Beefboard. Retrieved 8 Dec 2008
  25. ^ a b "Benefits of Grazing Cattle on the Prairie". Native Habitat Organization. Retrieved 1 Dec 2008
  26. ^ Dalrymple, R.L.. "Fringe Benefits of Rotational Stocking". Intensive Grazing Benefits. Noble Foundation. Retrieved 1 Dec 2008
  27. ^ "Waterfowl Area Grazing Benefits Birds, Cattle". 21 002 2008 1-4. Retrieved 1 Dec 2008
  28. ^ "Bison Grazing Increases Biodiversity in Grasslands". Bio-Medicine. Retrieved 1 Dec 2008
  29. ^ Semi-natural Grasslands, National Ecosystem Assessment; http://uknea.unep-wcmc.org/LinkClick.aspx?fileticket=Y4pLIpagaf0%3d&tabid=82
  30. ^ Mountains, Moorlands and Heahtlands, National Ecosystem Assessment; http://uknea.unep-wcmc.org/LinkClick.aspx?fileticket=3ef%2bGcq2VLw%3d&tabid=82
  31. ^ Forest rights.
  32. ^ Susan Jane Buck Cox - "No tragedy on the Commons" Journal of Environmental Ethics, Vol 7, Spring 1985 [1]

External links[edit]