Alternative analyses of repeated weight measurements of beef cattle

Revista Brasileira de Zootecnia

Freitas, Alfredo Ribeiro de²  Toral, Fábio Luiz Buranelo¹  Presotti, Cátia Valéria³ 

[1] UFV;Embrapa Pecuária Sudeste, São Carlos;UFSCar, São Carlos

关键词: Akaike's Information Criterion;    beef cattle;    Box-Cox transformation;    covariance structures selection;    Schwarz's Bayesian Criterion    IntroduçãoNo estudo do desenvolvimento ponderal de bovinos de corte;    a análise das pesagens realizadas no indivíduo;    dentro de determinado período;    pode compreender três aplicações:1) produzir testes estatísticos para efeitos fixos em regressão e análises de variância (ANAVA);    univariada e multivariada e estimar variâncias e covariâncias de efeitos aleatórios;    o procedimento tradicionalmente adotado é o GLM do SAS (SAS;    1999-2001);    que utiliza o método de quadrados mínimos (Azzalini;    1994;    Littel et al;   

DOI  :  10.1590/S1516-35982005000700010

学科分类：兽医学

来源: Universidade Federal de Vicosa

【 摘 要 】

Data consisting of individual records of male and female animals of purebred Bos Indicus beef cattle (Nellore, Guzerá, Gir and Indubrasil) weighted every three months from birth to 24 months of age available from National Archive of Brazilian Zebu Breeders Association (ABCZ) were used to evaluate two alternatives (co)variance analyses for body weight. In the first analysis the Box-Cox family transformation yil = (yl-l)/l (l ¹ 0) or yi = log yi, for l=0 was effective in reducing the asymmetry of the coefficients and variance heterogeneity for all weights and breeds. In the second analysis a usual standard mixed model for repeated measures was used to evaluate covariance structures which accounted for the within-individual variances using the goodness of fit criteria provided by PROC MIXED: c² distribution for the null hypothesis, Akaike's Information Criterion and Schwarz's Bayesian Criterion. The best covariance structure for all breeds was the Unstructured followed by the Factor-Analytic for Nellore, Gir and Indubrasil breeds and the Heterogeneous Composed Symmetry for the Guzera breed.

【 授权许可】

CC BY-NC