Effects of dietary energy level on the performance and carcass characteristics of lambs

The objective of this study was to evaluate the influence of ration energy levels on the performance and carcass characteristics of confined lambs. Four energy levels were evaluated: 2.00; 2.28; 2.54, and 2.80 Mcal of ME kg-1DM, with the last content being recommended by the National Research Council [NRC] (2007) for daily weight gains of 300 g. Twenty-four crossbred Ile de France ram lambs (six per treatment) at 240.0 ± 9.6 days of age and 26.6 ± 3.8 kg body weight, fed with isoprotein diets (158 g kg-1, CP) were used. The confinement lasted 57 days. Final body weight, cold carcass weight, and cold carcass yield were linearly and positively influenced by diet energy content. Food intake, average daily weight gain, and feed conversion were quadratically influenced by energy level, where the highest averages were observed under diets containing between 2.54 and 2.80 Mcal. In percentage terms, the main carcass cuts (leg and shoulder) were not influenced by diet energy level. In terms of the shoulder tissue composition, it was observed that bone content decreased linearly, fat content increased quadratically, and muscle content was not affected by the energy content of the diet. It was concluded that diets with higher energy densities lead to the production of heavier carcasses with higher yields, as well as increased weight gains. Optimal diets should therefore contain between 2.54 and 2.80 Mcal of ME kg-1DM.