Records of theweights at birth, weaning and monthly from 8 to 19 months of age from threegenetic groups: ½Canchim-Nellore (CN), ½Angus-Nellore (AN) e ½Simmental-Nellore(SN), born in 1998 and 1999 in Southeast Brazil, were used to fit a Logisticnonlinear model that included the fixed effects of the contemporary group andgenotype of the genes kappa-casein-HinfI (CSN3): AA and AB, growth hormone-AluI(GH): LL and LV, and b-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 differencesstarted at 12-13 months of age. The value of the maturing rate (k) ofthe 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 estimateof the asymptotic value (A) for the AA and AB genotypes in CN and SNgenetic groups. For the GH polymorphism there were inferior values of the parametersA and k to LL genotype in relation to LV genotype for the AN geneticgroup, however for the SN genetic group there was inferior value of the parameterA and superior value of the parameter k to LV genotype in relationto LL genotype. The same was observed for the LGB, there were superior valuesof the parameter k of the AA and AB genotypes in relation to the BB forthe AN genetic group, however, there was inferior value of the parameter kof the AB genotype in relation to the BB, for the SN genetic group.
