Effects of diets with high and low protein contents and two concentrate levels in Santa Ines×Texel lambs

Abstract

Two experiments were conducted to evaluate the effects of diets containing two levels of crude protein (CP) and concentrates on the intake, total nutrient digestibility, nitrogen balance (NB), microbial efficiency, and performance of lambs. The diets consisted of 10% or 14.25% CP and 40% or 60% concentrate, with corn silage as the forage. In the digestibility assay, four intact male F1 Santa Ines×Texel lambs, with an average body weight of 21.0±2.48 kg and rumen-cannulated, were used. The lambs were distributed in a 4×4 Latin square design with four treatments and four periods. There was no effect of the CP×concentrate interaction on the variables that were studied. There was an effect of CP levels on the intake and digestibility of CP, as well as on the amounts of N that were ingested, absorbed, and retained from urine (NB). There was also an effect of CP levels on uric acid excretion. In the performance assay, 32 intact F1 Santa Ines×Texel lambs with an average body weight of 19.0±2.02 kg were used. They were distributed in a 2×2 factorial arrangement of treatments in a randomized block design with eight replicates. There was a significant interaction between CP and concentrate levels on the ether extract (EE) intake. The CP level affected the intake of dry matter (DM), organic matter (OM), CP, neutral detergent fiber corrected for ash and protein (apNDF), non-fiber carbohydrates (NFC), total digestible nutrients (TDN), and rumen-degraded protein (RDP), as well as the carcass gain (CG) and the feed conversion (FC). Concentrate levels affected the intake of DM, OM, CP, NFC, TDN, and RDP, as well as the CG, the CG/average daily gain (ADG), and the FC. It was concluded that levels of CP and concentrate do not affect microbial efficiency or nutrient digestibility, except for CP digestibility. A high level of CP or concentrate in the diet results in greater nutrient intake and better animal performance.