Literature data indicate that feed intake is sensitive to the dietary Lys content particularly in fast-growing birds. From a conceptual and a practical viewpoint, an interaction between genotype (i.e., fast-growing vs. slow-growing birds) and dietary Lys content is of interest, but it needs confirmation owing to a dearth of studies addressing this issue. A study was conducted with 266 Cobb 500 birds and 266 Thai native crossbreed birds serving as models for fast-growing broilers ( FGB ) and slow-growing broilers ( SGB ), respectively. Within genotype, chicks were randomly allocated to diets containing either a high ( H-LYS = 1.36%), medium (1.17%), or low Lys (1.01%) content. Growth performance and the accretion of protein and selected amino acids were determined in birds from 1 to 21 d of age. Treatments were arranged in a factorial design with 6 replications/treatment. Low Lys vs. H-LYS caused a 42.1% lower feed intake in FGB ( P < 0.001), but not in SGB ( P = 0.596). The feed conversion ratio ( FCR (g feed/g BW gain)) was lowest in FGB ( P < 0.001) and increased with decreasing dietary Lys contents ( P < 0.001). The Lys induced increase in FCR, however, was more pronounced in SGB ( P = 0.025). The absolute protein gain (g/bird) was influenced by the Lys content of feed and decreased by ∼54% and ∼23% in FGB and SGB, respectively ( P < 0.001). The efficiency (% of intake) of protein accretion was found to be greater in FGB ( P ≤ 0.001) and decreased with decreasing dietary Lys ( P ≤ 0.001). The efficiency of Lys accretion was found to be negatively affected by the dietary Lys content in FGB ( P < 0.001) but not SGB ( P genotype × dietary Lys = 0.008). It can be concluded that a dietary Lys content of 1.01% does not safeguard both growth performance and body protein accretion efficiency in both FGB and SGB. The suboptimal growth performance in FGB, but not SGB, is partially counteracted by a Lys-induced reduction in feed intake.

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Objective: The present study was to investigate the extraction conditions of dietary fiber from dried cassava pulp (DCP) and cassava distiller's dried grains (CDG) under different NaOH concentrations, and the Fourier Transform Infrared (FTIR) was used to determine the dietary fiber components. Methods:The dried samples (DCP and CDG) were treated with various concentrations of NaOH at levels of 2, 4, 6, and 8% using a completely randomized design with 4 replications of each. After extraction, the residual DCP and CDG dietary fiber were dried in a hot air oven at 55-60 ºC. Finally, the oven dried extracted dietary fiber was powdered to a particle size of 1 mm. Both extracted dietary fibers were analyzed for their chemical composition and determined by FTIR. Results:The DCP and CDG treated with NaOH linearly or quadratically or cubically (p<0.05) increased the total dietary fiber (TDF) and insoluble fiber (IDF). The optimal conditions for extracting dietary fiber from DCP and CDG were under treatment with 6% and 4% NaOH, respectively, as these conditions yielded the highest TDF and IDF contents. These results were associated with the FTIR spectra integration for a semi-quantitative analysis, which obtained the highest cellulose content in dietary fiber extracted from DCP and CDG with 6% and 4% NaOH solution, respectively. The Principal Component Analysis (PCA) illustrated clear separation of spectral distribution in cassava pulp extracted dietary fiber (DFCP) and cassava distiller's dried grains extracted dietary fiber (DFCDG) when treated with 6% and 4% NaOH, respectively.