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Registro Completo |
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Biblioteca(s): |
Embrapa Caprinos e Ovinos. |
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Data corrente: |
07/04/2005 |
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Data da última atualização: |
13/04/2022 |
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Autoria: |
LEWIS, R. M.; EMMANS, G. C.; DINGWALL, W. S.; SIMM, G. |
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Título: |
A description of the growth of sheep and its genetic analysis. |
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Ano de publicação: |
2002 |
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Fonte/Imprenta: |
Animal Science, v. 74, pt 1, p. 51-62, 2002. |
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Idioma: |
Inglês |
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Conteúdo: |
The Gompertz is one of a family of growth functions that, when the environment (e.g.food, housing) is non- limiting, provides a useful description of growth as a comparatively simple, single equation. lt has three parameters of which the important ones are mature size, A, and the rate parameter, B. Estimates of A and B, however, are highly correlated and defining their separate values for individual animals is problematic. This problem was explored using five methods for estimating the parameters, or transformations of them, to describe the growth of two genotypes of Suffolk sheep kept under non-limiting conditions. One genotype was under selection for high lean growth rate and the other was its control. Live weights that were collected at least fortnightly from near birth to 150 days of age over a 9-year period on 1934 lambs were used. The Gompertz form adequately described the growth of the great majority of the lambs evaluated. When considering A and B as a lumped parameter, Z = A.B, and fitting Z, B and an initial condition (a transformed birth weight) as the parameters, the problems in estimation were substantially overcome as shown by a low correlation of Z with estimates of B both within and across animais. Usefully Z has a biological interpretation in that Z\e is the maximum daily growth rate. Since the Gompertz form adequately described growth in these sheep, the extent of genetic co-variation for the growth parameters values (A, B, Z) was estimated to determine if they were amenable to selection. A weighted univariate animal model was fitted. Mature size, A, and the rate parameter, B, were moderately heritable (0.37 (s.e. 0.04) and 0.38 (s.e. 0.05), respectively) as was live weight at 150 days of age (0.31 (s.e.0.06)). However there was a substantial negative genetic relationship between A and B (-0.48). Z was highly heritable (0.72 (s.e. 0.05)). After 9 years of selection, the genotype selected for high lean growth rate was heavier (P < 0.001) at 150 days of age (5.2 kg) and at maturity (6.6kg), with a maximum growth raie (Z\e) that was 1.12 times that of the control. Our lumped parameter Z, in effect a rate parameter scaled for mature size, avoided problems in estimating A and B and, in so doing, offers a general and robust description of lamb growth amenable to selection. MenosThe Gompertz is one of a family of growth functions that, when the environment (e.g.food, housing) is non- limiting, provides a useful description of growth as a comparatively simple, single equation. lt has three parameters of which the important ones are mature size, A, and the rate parameter, B. Estimates of A and B, however, are highly correlated and defining their separate values for individual animals is problematic. This problem was explored using five methods for estimating the parameters, or transformations of them, to describe the growth of two genotypes of Suffolk sheep kept under non-limiting conditions. One genotype was under selection for high lean growth rate and the other was its control. Live weights that were collected at least fortnightly from near birth to 150 days of age over a 9-year period on 1934 lambs were used. The Gompertz form adequately described the growth of the great majority of the lambs evaluated. When considering A and B as a lumped parameter, Z = A.B, and fitting Z, B and an initial condition (a transformed birth weight) as the parameters, the problems in estimation were substantially overcome as shown by a low correlation of Z with estimates of B both within and across animais. Usefully Z has a biological interpretation in that Z\e is the maximum daily growth rate. Since the Gompertz form adequately described growth in these sheep, the extent of genetic co-variation for the growth parameters values (A, B, Z) was estimated to determine if ... Mostrar Tudo |
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Palavras-Chave: |
Função Gompeets; Genetic parameters; Gompertz function; Melhoramento genético. |
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Thesagro: |
Crescimento; Genética Animal; Ovino; Parâmetro Genético. |
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Thesaurus Nal: |
Animal genetics; Growth factors; Sheep. |
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Categoria do assunto: |
L Ciência Animal e Produtos de Origem Animal |
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Marc: |
LEADER 03090naa a2200289 a 4500
001 1531092
005 2022-04-13
008 2002 bl uuuu u00u1 u #d
100 1 $aLEWIS, R. M.
245 $aA description of the growth of sheep and its genetic analysis.
260 $c2002
520 $aThe Gompertz is one of a family of growth functions that, when the environment (e.g.food, housing) is non- limiting, provides a useful description of growth as a comparatively simple, single equation. lt has three parameters of which the important ones are mature size, A, and the rate parameter, B. Estimates of A and B, however, are highly correlated and defining their separate values for individual animals is problematic. This problem was explored using five methods for estimating the parameters, or transformations of them, to describe the growth of two genotypes of Suffolk sheep kept under non-limiting conditions. One genotype was under selection for high lean growth rate and the other was its control. Live weights that were collected at least fortnightly from near birth to 150 days of age over a 9-year period on 1934 lambs were used. The Gompertz form adequately described the growth of the great majority of the lambs evaluated. When considering A and B as a lumped parameter, Z = A.B, and fitting Z, B and an initial condition (a transformed birth weight) as the parameters, the problems in estimation were substantially overcome as shown by a low correlation of Z with estimates of B both within and across animais. Usefully Z has a biological interpretation in that Z\e is the maximum daily growth rate. Since the Gompertz form adequately described growth in these sheep, the extent of genetic co-variation for the growth parameters values (A, B, Z) was estimated to determine if they were amenable to selection. A weighted univariate animal model was fitted. Mature size, A, and the rate parameter, B, were moderately heritable (0.37 (s.e. 0.04) and 0.38 (s.e. 0.05), respectively) as was live weight at 150 days of age (0.31 (s.e.0.06)). However there was a substantial negative genetic relationship between A and B (-0.48). Z was highly heritable (0.72 (s.e. 0.05)). After 9 years of selection, the genotype selected for high lean growth rate was heavier (P < 0.001) at 150 days of age (5.2 kg) and at maturity (6.6kg), with a maximum growth raie (Z\e) that was 1.12 times that of the control. Our lumped parameter Z, in effect a rate parameter scaled for mature size, avoided problems in estimating A and B and, in so doing, offers a general and robust description of lamb growth amenable to selection.
650 $aAnimal genetics
650 $aGrowth factors
650 $aSheep
650 $aCrescimento
650 $aGenética Animal
650 $aOvino
650 $aParâmetro Genético
653 $aFunção Gompeets
653 $aGenetic parameters
653 $aGompertz function
653 $aMelhoramento genético
700 1 $aEMMANS, G. C.
700 1 $aDINGWALL, W. S.
700 1 $aSIMM, G.
773 $tAnimal Science$gv. 74, pt 1, p. 51-62, 2002.
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Embrapa Caprinos e Ovinos (CNPC) |
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