The objectivesof this study were to evaluate the environmental effects (age of dam at lambing,type of birth and sex of lamb) and genetic groups (Santa Inês and ½Santa Inês) on weight and morphometric measurements (heart girth, bodylength and height) of lambs; to test linear and allometric regressions to predictthe weight through the measurements; and to describe the type of growth of themeasurements from weight. Weight and morphometric measurements were sampledfrom birth to 154 days of age, at every 14 days. For the evaluation of the environmentalfactors and to predict the regressions the data of birth, weaning and 154 daysof age were used; and to determine the type of growth all the data collectedwere used. The lambs derived from younger (two-tooth) ewes recorded lower averagesthan the ones from eight-tooth ewes for weight, heart girth and body lengthat birth and length at weaning. The animals born from single births presentedhigher average weight from birth to weaning, as well as of all the measurementsfrom birth to 154 days of age than those from twin births. There was no differencebetween the genetic groups Santa Inês and ½ Santa Inês. Thecorrelations between the weight and measurements were significant, and it waspossible to predict the weight from the morphometric measurements through regressions.The type of weight gain with heart girth was isometric, while with length itwas positive allometric, and with height it was negative allometric. Thereby,in the absence of a scale it is possible to predict the weight from the morphometricmeasurements, and the type of birth is the most important factor that affectsthe development of lambs from birth to weaning.
