MODELOS DE REGRESSÃO ALEATÓRIA ATRAVÉS DO PESO CORPORAL EM CURVAS DE CRESCIMENTO DE AVES

Abstract

In modern genetic evaluations, random regression models have been used as a custom tool in order to analyze longitudinal traits such as the ones involved in animal growth. Such traits as body weight have an easy mensuration and an excellent response to selection, which is a suitable and important feature for animal breeding programs. The purpose of this review is to discuss about different random regression models that are involved in farm bird growth. The random regression models are recommended as an alternative to genetic evaluation of traits that are regularly measured during the animal life. These models allow the prediction of regression coefficients that represent the behavior of the additive genetic value for each animal in the specific evaluated trait in relation to time (age). Thus, interminable values for the independent variable are considered 340 Colloquium Agrariae, vol. 13, n. Especial, Jan–Jun, 2017, p. 321-347 ISSN: 1809-8215. DOI: 10.5747/ca.2017.v13.nesp.000238 within a defined interval, through deviations of each animal in relation to an estimated and fixed curve. The covariance component estimates assigned to random regression coefficients allow the covariance estimation between any values of the independent variable for a modeled random effect, which is accomplished by the covariance function. Therefore, random regression models improve the use of the weight information, when covariance structures between the studied ages are taken into account during the evaluation. They also allow the description of the estimated variance components that are involved in growth, besides granting presumptions for others in the curve inside the interval estimation.