The objective ofthis work was to calculate correction factors for the effects of age of thedam (AOD), age of the calf (AOC) and Julian birth date (DOB) on the averagedaily gain (ADG) from birth to weaning period of animals of Nellore breed. Thedata were analyzed by restricted maximum likelihood, using the animal model.The model included the fixed effects of contemporary group (CG), AOD, AOC andDOB, and the direct effects (animal), maternal, permanent environmental andresidue. The data were submitted to previous analysis for the definition ofsegmented polynomials to be used by means of SAS computing program where thecovariates sets were created. In the ADG study in function of AOD, was observeda quadractic-quadractic effect, and the dams reached the maturity between the5th and 7th years of age. The predicted ADG for the calvesincreased for the dams in the 4th and 6th years of age,as that the maximum gain was reached, decreasing from 6 up to 15 years of age,when the calves presented the lower gain rate. For AOC was observed a simplequadratic effect. The ADG presented an overall mean of .681 kg/day and decreasedas the animal age increased (from 156th to 308th day ofage). The Julian birth date showed a linear effect on the ADG, that decreasedin the period from 220th to 365th day of the Julian calendar.These two effects (AOC and DOB) were the most difficult to model: the "knots"and the segments of obtained polynomials at each step were dependent and, orinfluenced by the used modeling for the other effects, suggesting multicolinearityproblems and, or concentration of data in influent points. In function of theseproblems, a simplified modeling of the AOC and DOB effects was choose.
