The objective of this study was to evaluate the environmental effects (age of dam, type of birth, sex of the lamb and year of birth) and genetic groups on the weight and morphometric measurements of lamb at birth and at weaning; test regressions for predicting weight of lambs by the measurements and describe the type of growth of the measures. Lambs of young ewes (2 teeth) had lower average for all characteristics except height at weaning. The average birth weight ranged from 3.34 ± 0.14kg in the offspring of two teeth ewes to 3.94 ± 0.09kg in the lambs of eight teeth ewes, and for weaning weight ranged from 12.19 ± 0.72kg in the offspring of two teeth ewes, and 14.79 ± 0.62 in the lambs of six teeth ewes. The single birth lambs had highter averages than the twins. Means for birth weight ranged from 3.24 ± 0.11kg to 4.08 ± 0.06kg and for weaning weight from 11.18 ± 0.59kg to 15.81 ± 0.35kg, the averages were lower for twins and greater for single lambs. The genetic group affected the weight and the length and height at birth, where purebred Santa Inês lambs presented greater averages than ½ Santa Inês lambs. The year of birth influenced all traits. All correlations between weights and measures were significant. It is possible to predict the weight on the basis of measures.
allometric growth; body morphometry; body weight; sheep