Carcass characteristics and meat composition of lambs finished in feedlot with diets containing different levels of energy

The objective of this study was to evaluate the characteristics of the carcass, tissue composition in the section between 9(th) and 11(th) ribs, centesimal composition of Longissimus dorsi muscle and the proportion of the non-carcass components of non-castrated male lambs, fed in feedlot with diets containing 1.49, 1.55, 1.62 and 1.68 Mcal of net energy/kg of dry matter. Diets were composed by corn silage as the roughage and the concentrate was composed by a commercial ration and the energetic supplement Lacto Plus (R). It was used sixteen non-castrated male lambs, weaned at 74 +/- 18 days of age and slaughtered when they completed 84 days of feedlot. A completely ramdomized design was used, with four levels of energy, each one with four replicates. The percentage of leg linearly decreased while the percentage of rib linearly increased as the level of energy in the diet of the lambs improved. There was a linear decrease in the proportion of muscle and linear increase in the proportion of fat according to the level of energy in the diet. The centesimal composition of Longissimus dorsi muscle was not influenced by the level of energy of the diet. The percentages of blood and internal and kidney fat increased linearly while the percentages of full viscera and gastrointestinal content decreased linearly with the increase in energy level in the diets. Increasing levels of net energy in the diet of lambs in feedlot promotes reduction in the proportion of leg and increase the proportion of rib. Additionaly, it promotes an increase in proportion of fat and it reduces the proportion of muscle in the section between the 9(th) and 11(th) ribs.