Análise genética de resistência ao Rhipicephalus (Boophilus) microplus em bovinos cruzados Hereford x Nelore
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Data
2012-07-02
Autores
Ayres, Denise Rocha [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Com o objetivo de investigar a variação genética para característica resistência a carrapato e encontrar o modelo mais adequado para avaliação genética desta característica, foram utilizados dados de contagem de carrapato (CC) por infestação natural em bovinos cruzados Hereford x Nelore. Primeiramente os dados de CC obtidos de rebanhos localizados nos estados de Rio Grande do Sul (RS), Paraná (PR), Mato Grosso do Sul (MS) e São Paulo (SP) foram transformados para log10(CC+1) e agrupados em duas regiões, definidas por análise de agrupamento. Cada grupo foi considerado como uma característica diferente e com a utilização de um modelo bi-característica foram estimados os componentes de (co)variância e ainda avaliada a ocorrência de interação genótipo x ambiente para a característica. As estimativas de herdabilidade observadas para resistência à infestação por carrapatos foram baixas sugerindo que exista a possibilidade de seleção para animais resistentes a carrapato, porém com um lento progresso genético. Foi observada alta correlação genética para a característica contagem de carrapatos entre os dois grupos e não foi observada interação genótipo x ambiente para esta característica na população de estudo. Posteriormente, foi realizado um estudo comparativo quanto à habilidade preditiva e o ajuste de diferentes modelos para avaliação da característica contagem de carrapatos. Para isso foram utilizados três diferentes modelos de avaliação: linear com a utilização da transformação logarítmica das observações (MLOG); linear sem a transformação das observações (MLIN) e o linear generalizado Poisson com adição de um termo residual (MPOI). Foi utilizada validação cruzada para comparar a habilidade preditiva dos modelos. Uma discreta superioridade quanto à qualidade de ajuste...
Aiming to investigate the genetic variation of tick resistance and to find the Best fitting model for this trait, data of tick counting (TC) by natural infestation in Hereford Nellore cattle were used. Firstly, the data of TC obtained from herds located in the states of Rio Grande do Sul (RS), Parana (PR), Mato Grosso do Sul (MS) e São Paulo (SP) were transformed into log10(CC+1) and grouped into two regions, defined by cluster analysis. Each group was considered as a different trait, and by using a two-trait model, the covariance components were estimated, and also, the occurrence of genotype x environment interaction was evaluated for the trait. Estimates of heritability observed for TC were low, suggesting that there is a possibility of selecting animal that are resistant to tick infestation, however, with a low genetic progress. High genetic correlation for TC between both groups was estimated, and no genotype x environment interaction was observed for this trait in this population. After, a comparative study was performed regarding the predictive ability and the fitting of different models for the evaluation of TC. For that, three different evaluation models were used: linear with the use of logarithmic transformation of the data (MLOG); linear without the use of logarithmic transformation of the data (MLIN), and linear generalized Poisson with the addition of a residual term (MPOI). Cross validation was performed to compare the predictive ability of the models. A discreet superiority regarding the adjustment quality and the predictive ability were showed by the model MPOI. Correlations between observed and predicted TC were almost equal in all models and the highest rank correlation between EBVs was observed between... (Complete abstract click electronic access below)
Aiming to investigate the genetic variation of tick resistance and to find the Best fitting model for this trait, data of tick counting (TC) by natural infestation in Hereford Nellore cattle were used. Firstly, the data of TC obtained from herds located in the states of Rio Grande do Sul (RS), Parana (PR), Mato Grosso do Sul (MS) e São Paulo (SP) were transformed into log10(CC+1) and grouped into two regions, defined by cluster analysis. Each group was considered as a different trait, and by using a two-trait model, the covariance components were estimated, and also, the occurrence of genotype x environment interaction was evaluated for the trait. Estimates of heritability observed for TC were low, suggesting that there is a possibility of selecting animal that are resistant to tick infestation, however, with a low genetic progress. High genetic correlation for TC between both groups was estimated, and no genotype x environment interaction was observed for this trait in this population. After, a comparative study was performed regarding the predictive ability and the fitting of different models for the evaluation of TC. For that, three different evaluation models were used: linear with the use of logarithmic transformation of the data (MLOG); linear without the use of logarithmic transformation of the data (MLIN), and linear generalized Poisson with the addition of a residual term (MPOI). Cross validation was performed to compare the predictive ability of the models. A discreet superiority regarding the adjustment quality and the predictive ability were showed by the model MPOI. Correlations between observed and predicted TC were almost equal in all models and the highest rank correlation between EBVs was observed between... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Bovino de corte, Bovino - Parasito, Carrapato, Genetica animal, Animal genetics
Como citar
AYRES, Denise Rocha. Análise genética de resistência ao Rhipicephalus (Boophilus) microplus em bovinos cruzados Hereford x Nelore. 2012. iii, 61 f. Tese (doutorado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, 2012.