-Four experiments were conducted to determine the effects of carbohydrase (CS) supplements in pig diets on ileal digestibility and ammonia emission. The CS used in this study is composed of the enzymes obtained from Aspergillus niger and Aspergillus oryzae during their fermentation process. The major active enzymes were α-1,6-galactosidase, β-1,4-mannanase, and β-1,4-mannosidase that target flatulence producing compounds in soybean meals. In experience 1 (Exp. 1), 8 cannulated barrows (93.9 ± 2.0 kg) were fed diets with CS supplementation (0.00, 0.05 and 0.10%) in order to measure ileal nutrient digestibility. Ileal digestibilities of lysine, threonine, and tryptophan were improved (P < 0.05) with CS supplements at 0.05% and 0.10%, whereas digestibility of methionine and branched-chain amino acids did not improve. Supplementing 0.05% CS increased (P < 0.05) apparent ileal energy digestibility. In experience 2 (Exp. 2), 100 pigs (24.1 ± 0.6 kg) were fed either a control diet (3 278 Mcal ME per kg diet) or a low-energy diet (3 109 Mcal ME per kg diet) with 0.05% CS for 4-wk. No differences (P > 0.05) were observed for ADG, feed intake, and gain:feed between the pigs fed a low-energy diet with CS and the control during the entire 4-wk. In experience 3 (Exp. 3), 100 pigs (64.1 ± 1.7 kg) were fed either a control diet (3 277 Mcal ME per kg diet) or a low-energy diet (3 168 Mcal ME per kg diet) with 0.05% CS for 4-wk. Barrows fed the diet with CS grew faster and had an increased gain:feed (P < 0.05) than the control, whereas growth rate and gain:feed of the gilts was not improved by CS. In experience 4 (Exp. 4), 60 pigs (23.1 ± 1.7 kg) were fed either a control diet or a 0.05% CS supplemented diet (3 replicates per treatment with 10 pigs per pen). The pigs in each pen were moved to an environmental chamber and aerial ammonia levels were measured for 66 h at 5 min intervals but the first 18-h was regarded as an acclimation period and the last 48-h was regarded as the data collection period. There was no difference (P = 0.436) in the average ammonia concentration between the treatments. However, the increase in ammonia concentration was slower (P < 0.05) from pigs fed 0.05% CS than from pigs fed the control diet. These experiments indicate that the CS supplementation improves nutrient digestibility and could reduce at least 3% of ME in swine diets without adverse effects on growth performance. Résumé -Utilisation des carbohydrases dans les régimes à base de farine de maïs-soja chez le porc en croissance-finition. Quatre expériences ont été conduites pour déterminer les effets de l'addition de carbohydrases (CS) dans l'alimentation des porcs sur la digestibilité iléale des nutriments et l'émission d'ammoniac. Les carbohydrases utilisées dans cette étude ont été des enzymes obtenues à partir d'Aspergillus niger et Aspergillus oryzae durant le processus de fermentation. Les principales enzymes actives étaient l'α-1,6-galactosidase, la β-1,4-mannanase, et la β-1,4-mannosidase qui visent les composés à l'origine de ...

Fixed fluidized bed reactor is widely used to evaluate the crackability of heavy oils and the activity of catalysts. To understand the hydrodynamics, reaction kinetics and thermodynamics in conventional and modified fixed fluidized bed reactors, the computational fluid dynamics method, energy-minimization multi-scale-based two-fluid model coupled with a six-lump kinetic model was used to investigate the gas–solid flow and cracking reactions. The gas mixing and particle volume fraction distributions, as well as product yields in the conventional and modified fixed fluidized bed reactors were analyzed. The residence time distribution model was utilized to obtain the parameters indicating the back-mixing degree, such as mean residence time and dimensionless variance of the gas. The results showed that the simulated product distribution is in reasonable agreement with the experimental data; the modified fixed fluidized bed reactor is closer to the ideal plug flow reactor, which can efficiently enhance the gas–solid mixing, reduce the gas back-mixing degree, and hence improve the reaction performance.