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Resumo -O objetivo deste trabalho foi estabelecer a influência do reprodutor e da alimentação sobre o desempenho de cordeiros em confinamento. O delineamento experimental foi o inteiramente casualizado, com arranjo fatorial 2x4, costituído de dois grupos genéticos (Santa Inês x sem raça definida (SRD) e Somalis x SRD) e concentrado de milho em gão, farelo de soja e sal mineral a 15%, 30%, 45% e 60%. Trinta e dois animais foram confinados em baias individuais e cada um constituiu uma repetição. As dietas eram compostas de feno de leucena (Leucaena leucocephala) e concentrado, na forma de ração completa. O aumento de concentrado na dieta dos animais causou incrementos lineares (P<0,05) no peso de abate e melhoria na conversão alimentar. Houve efeito quadrático no consumo de matéria seca e de matéria orgânica, com máximos estimados em 35,29% e 35,36% de concentrado, respectivamente. Todas as margens brutas de lucro estimadas foram positivas. Não houve diferença (P>0,05) entre os concentrados, porém o grupo genético Somalis x SRD mostrou-se superior (P<0,05) ao Santa Inês x SRD.Termos para indexação: Leucaena leucocephala, feno, ingestão de alimento, eficácia alimentar, ganho de peso, ovino. Influence of genetic group and feeding on performance of lambs in confinementAbstract -The objective of this work was to establish the influence of breeding ram and feeding on performance of lambs in confinement. The experimental design was completely randomized, in a 2x4 factorial arrangement. The treatments were two genetic groups (Santa Inês x not defined breed (NDB) and Somalis x NDB) and concentrate (corn, soybean meal plus mineral salt) at 15%, 30%, 45% and 60%. Thirty two animals were confined in individual stalls and each was one repetition. The diets were composed by concentrate and roughage, leucaena hay (Leucaena leucocephala), as a complete ration. The slaughter weight increased and the feed efficiency improved (P<0.05) as concentrate in diet was increased. A quadratic effect on dry matter intake and organic matter intake with maximum values of 35.29% and 35.36%, respectively, was observed. All estimated gross margin were positive. There was no difference (P>0.05) among concentrates; however, the genetic group Somalis x NDB was superior (P<0.05) to Santa Inês x NDB.

This study compares both versions of the nutritional requirement system determined by the National Research Council (NRC) version 1985 (NRC85) and NRC version 2007 (NRC07), for finishing lambs in feedlots. Nineteen crossbred lambs were divided in four groups representing four experimental treatments: one diet according to NRC85 and three diets according to NRC07. The diets recommended by NRC07 considers crude protein intake relative to ruminal undegradable protein at 20, 40, and 60 % levels (NRC07/20, NRC07/40, and NRC07/60). Diets were composed of Brazilian semi-arid native grass silage, soybean meal, corn, annatto byproduct, and limestone. Purchases and sales of lambs were done according to average market prices in Brazil. The economic indicators considered pointed that all treatments were viable but NRC07/20 and NRC07/60 were more profitable with similar net present values (NPVs) and internal return rates (IRRs). NRC07/20 was the best option showing an IRR of 17.20 % and a payback period (PP) of 5.07 considering a fixed annual interest rate of 6 %. Sensitivity analysis considering a 10 % raise in variable costs showed negative NPVs, IRRs inferior to the opportunity cost rates adopted and PPs that exceeded the planning horizon of 7 years for both NRC85 and NRC07/40.