ABSTRACT The objective of this study was to analyze the factors that influence the performance of lambs in pasture confinement, by substituting a concentrate with different levels of the aerial part of cassava in relation to hematocrit indices. The experiment was conducted at the Sheep Technology Center using 56 Pantaneira sheep, of which 28 were male and 28 were female. For female lambs, the globular volume showed a decreasing quadratic effect, with a minimum inclusion of 10.24% PAM in the diet for a hematocrit index of 32.28. A linear effect was observed for the mean crude protein intake in the male lambs based on the diet provided and was estimated to be equivalent to 87.4% of the lambs’ final weight. In conclusion, mean crude protein consumption is most strongly correlated with the final weight of male lambs, and NDF is most strongly correlated with the final weight of female lambs, with the level of cyanide consumption influencing the average daily weight gain in female lambs. The hematocrit level of the male lambs decreased with an increase in the inclusion of the aerial part of cassava in the ration of the animals.