| Technical note: a simple model to estimate changes in dietary composition of strip-grazed cattle during progressive pasture defoliations. | |
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MedLine Citation:
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PMID: 20630225 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Methodological problems occur in measuring herbage intake and diet quality during short-term (4-24h) progressive defoliations by grazing. Several models were developed to describe pasture component selection by grazing ruminants, particularly sheep. These models contain empirical coefficients to determine preferences that require laborious and data-demanding calibration. The objective was to develop a simple and practical model of changes in diet composition (green:dead) of pastures strip-grazed by dairy cows. The model was based on 3 premises when cows are strip-grazed in relatively homogeneous swards: 1) cows eat dead material only when green leaf and uncontaminated material have been removed; 2) dead material increases toward the bottom of the sward canopy; and 3) cows progressively defoliate pasture in layers. The main simplification in this model was assuming a linear decrease of green mass from the top to the bottom of the sward canopy. Thus, the proportion of green mass in the stratum eaten depended on the proportion of green in the entire sward canopy and its vertical profile. The model offers a simple solution to estimate changes in dietary compositions in pastures strip-grazed by dairy cattle during progressive pasture defoliations. It uses 2 inputs, the green mass proportion of the total herbage mass and the proportion of total herbage mass eaten during grazing. This can be optionally complemented with inputs of herbage chemical composition. The main outputs of the model are the proportions of green and dead herbage mass in the diet. For example, if the green proportion in the sward was 0.5 and the proportion of herbage mass eaten was 0.5, then the diet would be 0.75 green:0.25 dead; assuming 0.8 and 0.4 digestibility for green and dead material, respectively, the diet digestibility would be 0.7. |
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Authors:
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A J Romera; P Gregorini; P C Beukes |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of dairy science Volume: 93 ISSN: 1525-3198 ISO Abbreviation: J. Dairy Sci. Publication Date: 2010 Jul |
Date Detail:
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Created Date: 2010-07-15 Completed Date: 2010-12-14 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985126R Medline TA: J Dairy Sci Country: United States |
Other Details:
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Languages: eng Pagination: 3074-8 Citation Subset: IM |
Copyright Information:
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Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved. |
Affiliation:
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DairyNZ, Private Bag 3221, 3240 Hamilton, New Zealand. Alvaro.Romera@dairynz.co.nz |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animal Feed
/
analysis,
standards Animals Cattle / physiology* Diet / veterinary* Eating / physiology Female Models, Biological* Poaceae / metabolism |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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