The objective ofthis work was to study the effects of age of dam (AOD), age of calf (AOC) andJulian date of birth (DOB) on the average daily gain (ADG) from birth to weaningperiod of Nellore breed animals. The data were analyzed by restricted maximumlikelihood, using the animal model. The model included the direct effects ofcontemporary group (CG), AOD, AOC and DOB, and the direct effects (animal),maternal, permanent environmental and residue. The covariates were defined usingsegmented polynomials. In view of higher association between the AOC and DOBeffects and of the importance of these effects on ADG, estimates with thesetwo effects as a whole were selected. The correlation value between AOC andDOB of -0.60 was a poor indicator of the problems, being the three-dimensionalplot very useful. The AGD was significantly influenced by linear and quadraticeffects of calf age. The usual way to obtain adjusted weaning weights throughAGD can not be adequate for this data set. The julian birth date is an importanteffect on ADG and should be included in the model and a segmented polynomialfunction may be preferable to a discrete parameterization.
