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Registro Completo |
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Biblioteca(s): |
Embrapa Suínos e Aves. |
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Data corrente: |
22/05/1998 |
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Data da última atualização: |
11/07/2007 |
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Autoria: |
LEDUR, M. C. |
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Título: |
Genetic effects of aging in laying hens. |
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Ano de publicação: |
1997 |
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Fonte/Imprenta: |
Guelph: University of Guelph, 1997. |
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Páginas: |
145p. |
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Idioma: |
Inglês |
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Notas: |
Tese Doutorado |
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Conteúdo: |
This study reports on the effects of aging on fitness and non-fitness traits of laying hens during the first laying cycle. Age-related changes in mean heterosis, reciprocal effects, strain additive, Z-choromosome and heterotic effects, and their variances were estimated for hens housed one and three per cage. The expression of heterosis depended onage, trait, cross and environment. Mean heterosis increased in magnitude with age, except for specific gravity (SG), and albumen height (AH)with one bird per cage. Mean heterosis for egg number including mortality and morbidity (EPMM) decreased at the end of the cycle with three birds per cage, suggesting possible heterosis x environment interaction. Reciprocal effects were influenced by age, trait, cross and environment. Reciprocal effects were larger for egg number of survivors (EP) with three than with one bird per cage. Age-related in additive, Z-chromosome and effects varied among strains, showing that strains differ in their genetic response to aging. The pattern of change varied by environment suggesting possible genotype x environment interaction. Heterotic, environmental and phenotypic increased with age, except for AH with one bird per cage. Trends in additive and Z-chromosome variances varied depending on the traid and environment. For fitness traits, additive variance increased with age, except for hatchability, and EPMM with three birds per cage. The Z-chromosome variance decreased with age for fertility and hatchability and did not show any consistent trendfor EP nor EPMM. For non-fitness traits these variances increased withage, except for SG, and for AH with one bird per caage. Heritabilities, however, tended to decrease with age for most of the traits. Geneticvariance increased with age for all traits. Improvement of lifetime performance my be obtained by selecting animals at older ages, which would possibly favour individuals with better DNA repair or those who hadmore genes switched on or off during the course of aging. As the relative increased with age in additive variance was larger for fitness than for non-fitness traits, selection for egg quality traits should be performed at early stages. MenosThis study reports on the effects of aging on fitness and non-fitness traits of laying hens during the first laying cycle. Age-related changes in mean heterosis, reciprocal effects, strain additive, Z-choromosome and heterotic effects, and their variances were estimated for hens housed one and three per cage. The expression of heterosis depended onage, trait, cross and environment. Mean heterosis increased in magnitude with age, except for specific gravity (SG), and albumen height (AH)with one bird per cage. Mean heterosis for egg number including mortality and morbidity (EPMM) decreased at the end of the cycle with three birds per cage, suggesting possible heterosis x environment interaction. Reciprocal effects were influenced by age, trait, cross and environment. Reciprocal effects were larger for egg number of survivors (EP) with three than with one bird per cage. Age-related in additive, Z-chromosome and effects varied among strains, showing that strains differ in their genetic response to aging. The pattern of change varied by environment suggesting possible genotype x environment interaction. Heterotic, environmental and phenotypic increased with age, except for AH with one bird per cage. Trends in additive and Z-chromosome variances varied depending on the traid and environment. For fitness traits, additive variance increased with age, except for hatchability, and EPMM with three birds per cage. The Z-chromosome variance decreased with age for fertility and hatchabil... Mostrar Tudo |
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Palavras-Chave: |
Laying hen; Melhoramento genetico; Poedeira. |
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Thesaurus Nal: |
breeding; genetics. |
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Categoria do assunto: |
-- |
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Marc: |
LEADER 02664nam a2200193 a 4500
001 1433129
005 2007-07-11
008 1997 bl uuuu m 00u1 u #d
100 1 $aLEDUR, M. C.
245 $aGenetic effects of aging in laying hens.
260 $aGuelph: University of Guelph$c1997
300 $a145p.
500 $aTese Doutorado
520 $aThis study reports on the effects of aging on fitness and non-fitness traits of laying hens during the first laying cycle. Age-related changes in mean heterosis, reciprocal effects, strain additive, Z-choromosome and heterotic effects, and their variances were estimated for hens housed one and three per cage. The expression of heterosis depended onage, trait, cross and environment. Mean heterosis increased in magnitude with age, except for specific gravity (SG), and albumen height (AH)with one bird per cage. Mean heterosis for egg number including mortality and morbidity (EPMM) decreased at the end of the cycle with three birds per cage, suggesting possible heterosis x environment interaction. Reciprocal effects were influenced by age, trait, cross and environment. Reciprocal effects were larger for egg number of survivors (EP) with three than with one bird per cage. Age-related in additive, Z-chromosome and effects varied among strains, showing that strains differ in their genetic response to aging. The pattern of change varied by environment suggesting possible genotype x environment interaction. Heterotic, environmental and phenotypic increased with age, except for AH with one bird per cage. Trends in additive and Z-chromosome variances varied depending on the traid and environment. For fitness traits, additive variance increased with age, except for hatchability, and EPMM with three birds per cage. The Z-chromosome variance decreased with age for fertility and hatchability and did not show any consistent trendfor EP nor EPMM. For non-fitness traits these variances increased withage, except for SG, and for AH with one bird per caage. Heritabilities, however, tended to decrease with age for most of the traits. Geneticvariance increased with age for all traits. Improvement of lifetime performance my be obtained by selecting animals at older ages, which would possibly favour individuals with better DNA repair or those who hadmore genes switched on or off during the course of aging. As the relative increased with age in additive variance was larger for fitness than for non-fitness traits, selection for egg quality traits should be performed at early stages.
650 $abreeding
650 $agenetics
653 $aLaying hen
653 $aMelhoramento genetico
653 $aPoedeira
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Embrapa Suínos e Aves (CNPSA) |
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