Selection for Weaning Weight and Postweaning Gain in Hereford Cattle. II. Response to Selection

Irgang, Renato; Eu, Dillard; Mw, Tess; Ow, Robison

doi:10.2527/jas1985.6051142x

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…Frahm 1975; Chevraux and Bailey 1977;Barlow 1978; Irgang et al 1985; Sharma et al 1985). In a seiection study in which Hereford and Angus cattle were selected for rapid postweaning gain on high-energy or lowenergy diets, performance of male progeny after 12 yr of selection was compared with that of contemporary progeny resulting from the use of frozen semen from foundation sires (Bailey and Lawson 1986).…”

mentioning

confidence: 99%

Rate and Efficiency of Gain in Hereford and Angus Bulls From Lines Selected for Rapid Growth on High-Energy and Low-Energy Diets

Bailey¹,

Lawson²

1989

Can. J. Anim. Sci.

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. 1989. Rate and efficiency of gain in Hereford and Angus bulls from lines selected for rapid growth on high-energy and low-energy diets. Can. J. Anim. Hereford and Angus bull calves were obtained from lines selected for an average of 18 yr for rapid growth on a high-energy diet (concentrate) or a low-energy diet (forage). They were given a typical feedlot diet(70% concentrate and30% forage) in amounts about equal to 95% of the ad libitum intake and were slaughtered at a liveweight of 500 kg. Effects ofbreed, or ofthe selection diet given to the antecedents ofthe bulls, on rate and efficiency of gain of empty body, carcass, fat, protein, and energy were measured. Selection diet had no effect on rate or energetic efficiency of gain of the empty body or any of its constituents, nor on the distribution of the constituents of the gain between the carcass and the noncarcass portions of the empty body. This suggests that both selection diets exerted the same selection pressure for improved growth rate and feed efficiency when offspring resulting from selection were provided with a common high-energy diet and that either type of diet would, therefore, be appropriate for selecting animals for production systems that use high-energy diets. It was suggested that the main effect of selection was to increase the mature weight of the offspring. Comparing breeds, it was noted that Hereford bulls were heavier at birth, grew more slowly to weaning but more efficiently thereafter, and their carcasses were a smaller proportion of empty live weight than were those of Angus bulls. Animals were weighed every 2 wk, at 16 h after the previous feeding, and the allotment of feed was adjusted at that time. The animals were bedded on wood shavings and were allowed trace-mineralized salt and water free choice.Both concentrate and alfalfa cubes were sampled every day throughout the 4 yr of the experiment and the samples were pooled into one large batch that was used for a digestion trial at the end of the experiment. Composition and digestibility data are given in Table2. Procedures used for carrying out the digestibility trials were as described in an earlier report Maintenance energy requirements were estimated from a subsidiary experiment in which 24 bulls ranging from 280 to 520 kg liveweight were provided enough of the present feed, (70% concentrate, 3O% hay) to satisry their maintenance requirements according to data compiled by van Es (1978Es ( , 1980, and allowing their weights to reach equilibrium. This approach was based on the finding that body weights of cattle on fixed energy intakes eventually stabilized and remained fairly constant over long periods of time (Taylor et al. 1981

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confidence: 99%

Rate and Efficiency of Gain in Hereford and Angus Bulls From Lines Selected for Rapid Growth on High-Energy and Low-Energy Diets

Bailey¹,

Lawson²

1989

Can. J. Anim. Sci.

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“…Estimativas obtidas por meio de análises de quadrados mínimos desta mesma população, i ncluindo os animais nascidos até 1995, além dos parâmetros populacionais, foram relatadas por Razook et al (1998) As diferenças nos valores genéticos do peso à seleção no decorrer do tempo refletem as diferentes tendências realizadas nos rebanhos (Parnell et al, 1997 (Irgang et al, 1985;Baker et al, 1991;Koch et al, 1994;Parnell et al, 1997, entre outros). Entretanto, a metodologia de modelos mistos, em particular a análise de máxima verossimilhança com um modelo animal, parece fornecer ferramentas que permitem um entendimento melhor dos resultados dos experimentos de seleção (Meyer & Hill, 1991;Baker et al, 1991;Martinez et al, 2000).…”

Section: Análise Dosunclassified

Análise de um experimento de seleção para crescimento em bovinos nelore: respostas direta no peso ao sobreano e correlacionadas no tamanho e reprodução das matrizes.

Mercadante¹

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, com certeza o co-orientador não oficial deste trabalho, pelas longas discussões que muito contribuíram na condução das análises e na interpretação dos resultados. Aos amigos Joslaine Cyrillo, pesquisadora da Estação Experimental de Zootecnia de Sertãozinho e Cláudio de Mello, doutorando do Departamento de Produção Animal da ESALQ/USP, pela paciência de ler todo o texto e pelas valiosas sugestões. Aos Professores e Funcionários do Departamento de Produção Animal da ESALQ/USP, que me acolheram com muito carinho e atenção, em especial às secretárias Cláudia Chuahy e Vera Graciano. Aos amigos e colegas de curso, em especial à Ana Carolina Espasandin e Juliana Giannotti pelo apoio incondicional nos momentos fáceis e difíceis, e ao Eduardo Beserra e Odinete Murari pela companhia nas longas peixadas e cervejadas na Rua do Porto. À minha família, mãe e irmãs, pelos muitos feriados e finais de semana em que tomaram conta do Rodrigo. À Diretora e às Professoras do CCin, Centro de Convivência Infantil da ESALQ, pela seriedade e competência com que conduzem a educação dos filhos dos funcionários, professores e alunos, e à m inha secretária Maria D'Ajuda pelo carinho e dedicação dispensados ao Rodrigo. v Ao Instituto de Zootecnia, pelo afastamento concedido sem o qual não seria possível a obtenção desse título. Ao colega e chefe da Estação Experimental de Zootecnia de Sertãozinho, Leopoldo Andrade de Figueiredo, que me apoiou no pedido e manutenção do afastamento. Ao Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) pela bolsa concedida, um excelente estímulo para a obtenção do título de Doutor.

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“…While this is the most common approach used in the literature, by assuming the wrong residual error structure it significantly underestimates the standard error for the slope. Richardson et al (1968) and Irgang et al (1985) noted that when the number of individuals M t used to obtain the sample mean varies over generations, that those points based on more individuals contant more information and smaller residual errors. In this setting, the residual variances (roughly σ 2 z /M t ) are no longer homoscedastic, with these authors suggestion that a simple weighted least-squares method (e.g., LW Example 8.11) be used to correct for this.…”

Section: Cumulative Responsementioning

confidence: 99%

“…Hence, variance in the sample mean from r replicate lines with N * and M * is the same as the variance with a single line with N and M , provided that the number of individuals within each replicate line is sufficiently large to avoid significant inbreeding. Richardson et al (1968), Irgang et al (1985), and Muir (1986a,b) develope regression approaches correcting for between-generation environmental changes when replicate lines are used.…”

Section: Replicate Linesmentioning

confidence: 99%

Analysis of Short-term Selection Experiments: 1. Least-squares Approaches

Walsh¹,

Lynch²

2018

Oxford Scholarship Online

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This chapter examines short-term (a few generations) selection response in the mean of a trait. Traditionally, such experiments are analyzed using least-squares (LS) approaches. While ordinary LS (OLS) is often used, genetic drift causes the residual to be both correlated and heteroscedastic, resulting in the sampling variances given by OLS being too small. This chapter details the appropriate general LS (GLS) approaches to properly account for this residual error structure. It also reviews some of the common features observed in short-term selection experiments and examines experimental designs, such as the use of a control population versus a divergence-selection approach. It concludes by discussing another linear model used mainly by plant breeders, generation-means analysis (GMA), wherein remnant seed for several generations of response are crossed and then grown in a common garden. Such an analysis can provide insight into the genetic nature of any response.

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Selection for Weaning Weight and Postweaning Gain in Hereford Cattle. II. Response to Selection

Cited by 11 publications

References 10 publications

Rate and Efficiency of Gain in Hereford and Angus Bulls From Lines Selected for Rapid Growth on High-Energy and Low-Energy Diets

Rate and Efficiency of Gain in Hereford and Angus Bulls From Lines Selected for Rapid Growth on High-Energy and Low-Energy Diets

Análise de um experimento de seleção para crescimento em bovinos nelore: respostas direta no peso ao sobreano e correlacionadas no tamanho e reprodução das matrizes.

Analysis of Short-term Selection Experiments: 1. Least-squares Approaches

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