Records of the weights at birth, weaning and monthly from 8 to 19 months of age from three genetic groups: ½Canchim-Nellore (CN), ½Angus-Nellore (AN) e ½Simmental-Nellore (SN), born in 1998 and 1999 in Southeast Brazil, were used to fit a Logistic nonlinear model that included the fixed effects of the contemporary group and genotype of the genes kappa-casein-HinfI (CSN3): AA and AB, growth hormone-AluI (GH): LL and LV, and beta-lactoglobulin-HaeIII (LGB): AA, AB and BB, to examine the effect of these markers on the growth curve. The Logistic model used to explain the growth of the CN, AN and SN genetic groups, was influenced by the genotypes of the CSN3, GH e LGB markers. The major differences started at 12-13 months of age. The value of the maturing rate (k) of the AA genotype for CSN3 was superior in relation to AB genotype in the CN, AN and SN genetic groups. However, there was observed small difference in estimate of the asymptotic value (A) for the AA and AB genotypes in CN and SN genetic groups. For the GH polymorphism there were inferior values of the parameters A and k to LL genotype in relation to LV genotype for the AN genetic group, however for the SN genetic group there was inferior value of the parameter A and superior value of the parameter k to LV genotype in relation to LL genotype. The same was observed for the LGB, there were superior values of the parameter k of the AA and AB genotypes in relation to the BB for the AN genetic group, however, there was inferior value of the parameter k of the AB genotype in relation to the BB, for the SN genetic group.
crossbred; candidate genes; genetic marker; Logistic model
