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Registro Completo |
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Biblioteca(s): |
Embrapa Pantanal. |
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Data corrente: |
05/07/1996 |
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Data da última atualização: |
11/09/1996 |
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Autoria: |
LOEHLE, C.; RITTENHOUSE, L. R. |
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Título: |
An analysis of forage preference indices. |
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Ano de publicação: |
1982 |
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Fonte/Imprenta: |
Journal of Range Management, v.35, n.3, p.316-319, May, 1982. |
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Idioma: |
Inglês |
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Conteúdo: |
Of those models currently used to describe the preference of animals for various plants under given conditions, all have serious shortcomings for purposes of accurately explaining the data, in the regression sense. When five equations, based in various ways on preference abailability, were used to estimate diets of cattle and sheep, no clear advantage of one expression over another could be found. All models tested with the sheep data resulted in increased predicted sums of squares compared with total sums of squares. In contrast, models tested with the cattle data showed some reduction in unexplained variation in diet estimates during the entire year, spring, and summer, but not during fall. This improvements was probably because the cattle pastures were more homogeneous than the sheep pastures and species were aggregated. The best model was Ratio 4 (preference - availability) but it requires a complex and expensive parameters estimation techniques. It was concluded that sampling problems combine with inadequacies of the preference indexes to prevent accurate representation of the concept of diet preference. It was also concluded that sampling problems arise when the fecal, rumen fistula, or esophageal fistual techniques are used to estimate diets. A technique for adjusting these techniques to make them suitable for predicting diets was descrikbed. Further investigation into animal behavior are needed to determine variables which affect what the animal perceives as being desirable in relation to what is available. MenosOf those models currently used to describe the preference of animals for various plants under given conditions, all have serious shortcomings for purposes of accurately explaining the data, in the regression sense. When five equations, based in various ways on preference abailability, were used to estimate diets of cattle and sheep, no clear advantage of one expression over another could be found. All models tested with the sheep data resulted in increased predicted sums of squares compared with total sums of squares. In contrast, models tested with the cattle data showed some reduction in unexplained variation in diet estimates during the entire year, spring, and summer, but not during fall. This improvements was probably because the cattle pastures were more homogeneous than the sheep pastures and species were aggregated. The best model was Ratio 4 (preference - availability) but it requires a complex and expensive parameters estimation techniques. It was concluded that sampling problems combine with inadequacies of the preference indexes to prevent accurate representation of the concept of diet preference. It was also concluded that sampling problems arise when the fecal, rumen fistula, or esophageal fistual techniques are used to estimate diets. A technique for adjusting these techniques to make them suitable for predicting diets was descrikbed. Further investigation into animal behavior are needed to determine variables which affect what the animal perceives as being d... Mostrar Tudo |
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Palavras-Chave: |
Analise de forragem; Analise de indice; Analysis; Analysis of forage; Indice de preferencia; Preference indices; Preferencia. |
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Thesagro: |
Forragem. |
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Thesaurus Nal: |
forage. |
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Categoria do assunto: |
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Marc: |
LEADER 02178naa a2200241 a 4500
001 1789694
005 1996-09-11
008 1982 bl --- 0-- u #d
100 1 $aLOEHLE, C.
245 $aAn analysis of forage preference indices.
260 $c1982
520 $aOf those models currently used to describe the preference of animals for various plants under given conditions, all have serious shortcomings for purposes of accurately explaining the data, in the regression sense. When five equations, based in various ways on preference abailability, were used to estimate diets of cattle and sheep, no clear advantage of one expression over another could be found. All models tested with the sheep data resulted in increased predicted sums of squares compared with total sums of squares. In contrast, models tested with the cattle data showed some reduction in unexplained variation in diet estimates during the entire year, spring, and summer, but not during fall. This improvements was probably because the cattle pastures were more homogeneous than the sheep pastures and species were aggregated. The best model was Ratio 4 (preference - availability) but it requires a complex and expensive parameters estimation techniques. It was concluded that sampling problems combine with inadequacies of the preference indexes to prevent accurate representation of the concept of diet preference. It was also concluded that sampling problems arise when the fecal, rumen fistula, or esophageal fistual techniques are used to estimate diets. A technique for adjusting these techniques to make them suitable for predicting diets was descrikbed. Further investigation into animal behavior are needed to determine variables which affect what the animal perceives as being desirable in relation to what is available.
650 $aforage
650 $aForragem
653 $aAnalise de forragem
653 $aAnalise de indice
653 $aAnalysis
653 $aAnalysis of forage
653 $aIndice de preferencia
653 $aPreference indices
653 $aPreferencia
700 1 $aRITTENHOUSE, L. R.
773 $tJournal of Range Management$gv.35, n.3, p.316-319, May, 1982.
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Registro original: |
Embrapa Pantanal (CPAP) |
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