Author
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Aiken, Glen |
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Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/9/2015 Publication Date: 8/1/2016 Citation: Aiken, G.E. 2016. Grazing management options in meeting objectives of grazing experiments. Professional Animal Scientist. 32:1-9. Interpretive Summary: Grazing research has a long history of generating applicable information and technologies to livestock producers, as well as improving our understanding and knowledge of the biology and ecology of defoliated grasslands. Pasture measures using livestock productivity rather than mowing or other simulation means are essential in providing results that are applicable to farming practices, but variation in animals and pastures are major sources of error that can bias results if inappropriate experimental designs or sampling techniques are used. Two decisions are critical when planning any grazing experiment. First, should grazing be controlled to maintain an optimum grazing pressure by varying stocking rates over the grazing season as forage growth patterns change, or should stocking be fixed over a range of stocking rates to measure animal performance over under- and over-grazing scenarios. Second, should experimental pastures be continuously stocked, with grazing animals being kept in the same pasture for the duration of grazing, or should they be rotationally stocked, which rotates animals through subdivisions of pastures to facilitate pasture regrowth and recovery from grazing. A literature review will address the advantages and disadvantages of using each of these grazing management options. Technical Abstract: Decisions on which grazing management option to use in grazing experiments can be critical in meeting research objectives and generating information for the scientific community or technologies that meets the needs of forage-based enterprises. It is necessary to have an understanding of animal performance relationships with stocking rate, forage mass (FM), and forage allowance in order to make informed decisions on how to best manage forages and grazing in an experiment. Stocking rates can be varied using the put-and-take procedure to maintain the optimum grazing pressure as forage growth varies during the grazing season. The alternative to put-and-take stocking is to use a range of fixed stocking rates (SR) that generate light to heavy grazing pressure responses. Put-and-take controls grazing pressure in evaluating animal performance and stocking rate responses to treatments, while fixed stocking rates control SR to evaluate animal performance and grazing pressure responses treatments and treatment by SR interactions. Decisions to use either continuous or rotational stocking methods will be based on a need to complement existing grazing practices of the forage-based livestock industry or to determine best management practices. Relationships of animal performance with stocking rates, FM, and forage allowance will be presented and used to discuss the advantages and disadvantages of put-and-take and fixed stocking procedures, and the considerations in using either continuous or rotational stocking methods. |
