Análise da curva de crescimento difásica de fêmeas Hereford por meio da função não linear de Gompertz

Abstract

This study had the objective to compare weight difasics Gompertz models applied in the study of Hereford females growth curves and to modeling the errors structure inherent to each model. The non-linear difasic Gompertz growth models were adjusted with three different errors structures: independent errors (IE), first-class auto-regressive (AR (1)) and second-class auto-regressive (AR (2)) to weight-age data of 55 Hereford females, evaluated since birth till 675 days old. The comparison between the models was carried out through on the biological interpretation basis of the parameters and in the adjustment of quality appraisers (adjusted determination coefficient, Durbin-Watson test, residual standard desviation, iterations number), beyond the Akaike information criteria (AIC) and the F test to model comparison. All studied functions, although showed good data adjustment, tend to sub estimate the adult animal weight.