Fitting of fixed regression curves with different residual variance structures for Nellore cattle growth modeling.
Fitting of fixed regression curves with different residual variance structures for Nellore cattle growth modeling.
Author(s): CAVALCANTE, D. H.; SOUSA JÚNIOR, S. C.; SILVA, L. P.; MALHADO, C. H. M.; MARTINS FILHO, R.; AZEVEDO, D. M. M. R.; CAMPELO, J. E. G.
Summary: Different polynomial functions were tested for mean trajectory modeling with different residual variance structures. A total of 15,148 weight records of 3,115 Nellore Mocho cattle with ages between 1 and 660 days, raised in northern Brazil. First, the mean trajectory of cattle growth curve was fitted by a fixed regression using orthogonal polynomials with orders ranging from two to seven. Analyses were performed using the least-squares method, disregarding animal and/ or maternal random effects. Then, the best model was evaluated using different residual variance structures and homogeneous and heterogeneous classes. We considered as fixed effects those of groups of contemporary and of dam age at birth (as linear and quadratic covariate). The random model part included animal and maternal effects (direct genetic and permanent environments). We concluded that the estimates of variance components and genetic parameters were affected by both fixed regression curve polynomial order and residual variance structure. Moreover, random regression model considering an order-four polynomial function with a fixed curve and six-class residual variance showed better fits.
Publication year: 2020
Types of publication: Journal article
Unit: Embrapa Mid-North
Observation
Some of Embrapa's publications are published as ePub files. To read them, use or download one of the following free software options to your computer or mobile device. Android: Google Play Books; IOS: iBooks; Windows and Linux: Calibre.
Access other publications
Access the Agricultural Research Database (BDPA) to consult Embrapa's full library collection and records.
Visit Embrapa Bookstore to purchase books and other publications sold by Embrapa.