Estudo do valor adaptativo anual de fêmeas da raça Nelore utilizando modelos de regressão aleatória
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Data
2011-02-16
Autores
Pessoa, Matilde da Conceição [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O Objetivo deste trabalho foi avaliar o valor adaptativo anual para possível utilização como critério de seleção para a eficiência reprodutiva de fêmeas da raça Nelore. Foram estudadas medidas de valor adaptativo do 4º ao 13º ano de permanência no rebanho de 21.610 fêmeas. Os valores adaptativos anuais foram calculados com base na capacidade de sobrevivência e no número de crias deixado ano após ano. O modelo de melhor ajuste aos dados, segundo os critérios adotados, foi o de 5ª ordem para a tendência média da população, 5ª ordem para o efeito genético aditivo direto e 3ª ordem para efeito de ambiente permanente de animal. O modelo heterogêneo com 10 classes foi o mais adequado na modelagem da das variâncias residuais. As herdabilidades para valor adaptativo anual aumentaram com a idade dos animais (0,05 a 0,55). As correlações entre os valores adaptativos em diferentes idades foram baixas nas idades menores e altas entre as idades adultas. A tendência genética para valor adaptativo anual foi realizada com base nos valores genéticos preditos referentes às medidas adaptativas do 4º (Pti4), 8º(Pti8) e 13º(Pti13) ano de idade. Como critério de comparação foram utilizadas as características idade ao primeiro parto (Ipp) e stayability (Stay). As associações entre os valores genéticos preditos das características foram feitas utilizando a correlação de Pearson e porcentagem de touros coincidentes. Estimativas de herdabilidade para Ipp, Stay1 e Stay2 foram respectivamente 0,12, 0,33 e 0,40. As tendências genéticas indicaram que houve ganhos para Pti4 e Pti13 e, para Pti8 as médias dos valores genéticos se mantiveram quase que constantes com o passar dos anos. As associações entre os valores genéticos indicaram maior associação entre valores genéticos preditos para valor adaptativo medido no 4º ano e valores genéticos preditos para as características Ipp e Stay
The objective of this study was to evaluate the annual Fitness as selection criteria for reproductive performance of Nelore cows. We studied measures of fitness of the 4th to the 13th year of stayability of 21,610 females. The annual fitness was calculated based on survivability and the number of offspring left year after year. The most appropriate model, according to criteria adopted, was a 5th order for the average trend of the population, 5th order for the direct genetic effect and 3th order for the permanent environmental effect of animal. The heterogeneous model with 10 classes was the most appropriated in modeling of residual variances. Heritability estimates for annual fitness increased with age of animals (0.05 to 0.55). The correlations between fitness at ages different were lower in younger ages, and high among the adult ages. The genetic trend for annual fitness was based on predicted breeding values to adaptive measures relating to the 4th (Pti4), 8th (Pti8) and 13th (Pti13) years of age. As criterion for comparison were used the traits age at first calving (IPP) and stayability (Stay). The associations between predicted breeding values of traits were made using Pearson correlation and percentage of bulls coincide. Heritability estimates for Ipp, and Stay1 Stay2 were respectively 0.12, 0.33 and 0.40. The genetic trends indicated that there were gains for Pti4 and Pti13, however for Pti8, the average genetic values remained almost constant over the years. The associations between breeding values indicate greater association between breeding values for annual fitness measured in year 4th year and the breeding values for the traits Ipp and Stay
The objective of this study was to evaluate the annual Fitness as selection criteria for reproductive performance of Nelore cows. We studied measures of fitness of the 4th to the 13th year of stayability of 21,610 females. The annual fitness was calculated based on survivability and the number of offspring left year after year. The most appropriate model, according to criteria adopted, was a 5th order for the average trend of the population, 5th order for the direct genetic effect and 3th order for the permanent environmental effect of animal. The heterogeneous model with 10 classes was the most appropriated in modeling of residual variances. Heritability estimates for annual fitness increased with age of animals (0.05 to 0.55). The correlations between fitness at ages different were lower in younger ages, and high among the adult ages. The genetic trend for annual fitness was based on predicted breeding values to adaptive measures relating to the 4th (Pti4), 8th (Pti8) and 13th (Pti13) years of age. As criterion for comparison were used the traits age at first calving (IPP) and stayability (Stay). The associations between predicted breeding values of traits were made using Pearson correlation and percentage of bulls coincide. Heritability estimates for Ipp, and Stay1 Stay2 were respectively 0.12, 0.33 and 0.40. The genetic trends indicated that there were gains for Pti4 and Pti13, however for Pti8, the average genetic values remained almost constant over the years. The associations between breeding values indicate greater association between breeding values for annual fitness measured in year 4th year and the breeding values for the traits Ipp and Stay
Descrição
Palavras-chave
Bovino de corte - Melhoramento genetico, Reprodução animal, Evolução, Beef cattle, Longitudinal data, Evolution, Reproduction
Como citar
PESSOA, Matilde da Conceição. Estudo do valor adaptativo anual de fêmeas da raça Nelore utilizando modelos de regressão aleatória. 2011. vii, 52 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, 2011.