Biological and economic performance of feedlot lambs feeding on diets with different energy densities

The objective of this study was to evaluate performance, carcass dressing and gross profit margin of lambs of different genotypes finished in feedlot with diets containing two levels of energy (2.40 Mcal/kg dry matter - DM or 2.90 Mcal/kg DM). Fifty-four non-castrated lambs of the following genotypes were used: Santa Ines, F1 Dorper x Santa Ines and F1 Santa Ines x undefined breed at approximately 150 d of age averaging 22.6 kg of live body weight. Lambs subjected to the diet containing 2.90 Mcal/kg DM stayed in feedlot for a shorter period of time. Moreover, they showed lower intake of dry matter and water in addition to greater daily weight gain and corporal score. There was interaction of feed conversion, carcass dressing yield and gross profit margin. The Dorper x Santa Ines lambs showed similar feed conversion in the two diets. However, Santa Ines lambs and Santa Ines x undefined breed lambs showed better feed conversion with the diet containing 2.90 Mcal/kg DM. The carcass dressings of the Santa Ines x undefined breed lambs were similar for both diets. Furthermore, the carcass dressing values were higher for the Santa Ines and Dorper x Santa Ines which received the diet with higher energy density. The gross profit margin is higher for Dorper x Santa Ines lambs in relation to genotype Santa Ines x undefined breed lambs when subjected to the diet with 2.40 Mcal/kg DM.