Genotypic parameters for egg production in pure breed hens by using random regression model

portuguesObjetivou-se testar diferentes estruturas de matrizes de (co)variâncias genotipicas e residuais em modelos de regressao aleatoria para modelar a producao de ovos do 5o ao 12o mes de idade de poedeiras das racas Plymouth Rock Barrada e Plymouth Rock Branca, bem como estimar a herdabilidade no sentido amplo e as correlacoes ambientais e genotipicas. Foram avaliados seis modelos de regressao aleatoria e, para todos os modelos, foram testadas 12 estruturas das matrizes genotipicas e residuais. O modelo de regressao aleatoria com intercepto linear com estrutura de (co)variância desestruturada (UN) para a matriz de efeitos aleatorios e correlacao desestruturada (UNR) para a matriz de residuos, modela adequadamente a curva de producao de ovos das aves das duas racas estudadas. As correlacoes genotipicas variaram de 0.15 (entre o 5o e o 12o mes) a 0.99 (entre o 10o e o 11o mes), aumentando conforme a proximidade entre os meses. As herdabilidades para a producao de ovos entre o 5o e o 12o mes de idade aumentam com o avanco da idade, variando de 0.15 a 0.51. A partir do nono mes de idade a herdabilidade e moderada com estimativas de correlacoes genotipicas superiores a 90% nos meses 10, 11 e 12. Sugere-se a selecao das poedeiras atraves de criterios fenotipicos a partir do 9o mes de idade das aves. Palavras-chave: Plymouth Rock Barrada; herdabilidade; taxa de postura; Plymouth Rock Branca EnglishThis study aimed to test different genotypic and residual covariance matrix structures in random regression models to model the egg production of Barred Plymouth Rock and White Plymouth Rock hens aged between 5 and 12 months. In addition, we estimated broad-sense heritability, and environmental and genotypic correlations. Six random regression models were evaluated, and for each model, 12 genotypic and residual matrix structures were tested. The random regression model with linear intercept and unstructured covariance (UN) for a matrix of random effects and unstructured correlation (UNR) for residual matrix adequately model the egg production curve of hens of the two study breeds. Genotypic correlations ranged from 0.15 (between age of 5 and 12 months) to 0.99 (between age of 10 and 11 months) and increased based on the time elapsed. Egg production heritability between 5- and 12-month-old hens increased with age, varying from 0.15 to 0.51. From the age of 9 months onward, heritability was moderate with estimates of genotypic correlations higher than 90% at the age of 10, 11, and 12 months. Results suggested that selection of hens to improve egg production should commence at the ninth month of age. Key words: Barred Plymouth Rock; heritability; laying rate; White Plymouth Rock