Estimation of genetic parameters for milk yield in Murrah buffaloes by Bayesian inference
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Data
2010-02-01
Autores
Breda, F. C.
Albuquerque, Lucia Galvão de [UNESP]
Euclydes, R. F.
Bignardi, A. B. [UNESP]
Baldi, Fernando [UNESP]
Torres, R. A.
Barbosa, L.
Tonhati, Humberto [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Amer Dairy Science Assoc-adsa
Resumo
Random regression models were used to estimate genetic parameters for test-day milk yield in Murrah buffaloes using Bayesian inference. Data comprised 17,935 test-day milk records from 1,433 buffaloes. Twelve models were tested using different combinations of third-, fourth-, fifth-, sixth-, and seventh-order orthogonal polynomials of weeks of lactation for additive genetic and permanent environmental effects. All models included the fixed effects of contemporary group, number of daily milkings and age of cow at calving as covariate (linear and quadratic effect). In addition, residual variances were considered to be heterogeneous with 6 classes of variance. Models were selected based on the residual mean square error, weighted average of residual variance estimates, and estimates of variance components, heritabilities, correlations, eigenvalues, and eigenfunctions. Results indicated that changes in the order of fit for additive genetic and permanent environmental random effects influenced the estimation of genetic parameters. Heritability estimates ranged from 0.19 to 0.31. Genetic correlation estimates were close to unity between adjacent test-day records, but decreased gradually as the interval between test-days increased. Results from mean squared error and weighted averages of residual variance estimates suggested that a model considering sixth- and seventh-order Legendre polynomials for additive and permanent environmental effects, respectively, and 6 classes for residual variances, provided the best fit. Nevertheless, this model presented the largest degree of complexity. A more parsimonious model, with fourth- and sixth-order polynomials, respectively, for these same effects, yielded very similar genetic parameter estimates. Therefore, this last model is recommended for routine applications.
Descrição
Palavras-chave
covariance function, Genetic correlation, Heritability, test-day milk yield
Como citar
Journal of Dairy Science. Champaign: Amer Dairy Science Assoc-adsa, v. 93, n. 2, p. 784-791, 2010.