This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin (mTOR) signaling pathway and intestinal development of broilers. A total of 384 one-day-old broilers were randomly assigned into 4 treatments with 6 replicates (16 broilers per replicate). Broilers in these treatment groups were offered the following diets with 1.37, 1.77, 2.17 and 2.57% of leucine. These diet treatments were named 1.37TM, 1.77TM, 2.17TM, and 2.57TM. The experiment lasted 21 days and all birds had free access to feed and water. Results indicated that there was no significant difference in body weight, average daily gain and average feed intake among all treatments (P > 0.05). The broiler duodenal villus height in 2.57TM was the lowest, but the highest occurred in 1.37TM on d 7 and 14 (P < 0.05). The villus height in the jejunum and ileum increased along with leucine level from 1.37 to 2.17%. The villus height of jejunum was significantly higher in 2.17TM than in 1.37TM on d 7 and 14, and the ratio of villus height to crypt depth (V:C) in the duodenum, jejunum and ileum increased significantly (P < 0.05) on d 21. The gene expression level of mTOR in the duodenum decreased with increasing leucine level and was higher in 1.37TM than in 2.57TM on d 7 and 14 (P < 0.05). On d 14 and 21 of the trial, the expression of S6K1 in the duodenum was higher in 1.37TM than in 2.57TM (P < 0.05), and the expression of mTOR, S6K1 in the jejunum and ileum increased with increasing leucine level form 1.37 to 2.17%, whereas a significant difference occurred between 1.37TM and 2.17TM (P < 0.05). In conclusion, the addition of leucine fails to enhance the growth performance of broilers. However, leucine can improve intestinal development by enhancing villus height and V:C ratio in the jejunum and ileum. Moreover, the expression of mTOR, S6K1 increased as the level of dietary leucine was elevated from 1.37 to 2.17%.

The AME and net energy (NE) values of 4 corn varieties, including 2 normal corn varieties (Zheng Dan 958 and Xian Yu 335), and one each of waxy corn and sweet corn, and 2 soybean meal samples including regular (RSBM) and dehulled soybean meal (DSBM), were determined in 2 experiments for broiler breeding cocks using the indirect calorimetry method. The 4 test diets in Experiment 1 consisted of each test corn, which replaced 40% of the corn-soybean meal basal diet, and the test diets in Experiment 2 contained 25% RSBM or DSBM, which was used to replace the corn basal diet. Thirty (Experiment 1) or 18 (Experiment 2) 50-week-old Arbor Acre (AA) broiler breeding cocks were used in a completely randomized design. After a 7 d dietary adaptation period, 6 birds as replicates from each treatment were assigned to individual respiration chambers for energy measurement via gaseous exchange and total excreta collection for 10 d. In Experiment 1, the AME, ME intake (MEI), retained energy (RE), NE, and NE:AME ratio values were higher (P < 0.001) in the test diets as compared with the corn-soybean meal basal diet. The AME and NE values in the sweet corn diet were higher (P < 0.05) than those values in the other 3 test diets. The heat production (HP), fasting heat production (FHP), and respiration quotient (RQ) were not influenced by the various experimental diets. The respective AME and NE values were 3,785, 3,775, 3,738, and 3,997 kcal/kg (DM basis), and 2,982, 3,006, 2,959, and 3,146 kcal/kg (DM basis) for Zheng Dan 958, Xian Yu 335, waxy corn, and sweet corn. Birds fed a corn basal diet in Experiment 2 had higher AME, MEI, RE, NE, and NE:AME ratio values (P < 0.001). Soybean meal substitution had no effect on HP, FHP, or RQ. The average AME and NE content was 2,492 and 1,581 kcal/kg (DM basis) for RSBM, and 2,580 and 1,654 kcal/kg (DM basis) for DSBM, respectively.

This study was to investigate the effect of oxidized wheat gluten (OG) on growth performance, gut morphology and its oxidative states of broilers. One hundred and eighty-day-old male broilers (10 chicks/pen) were randomly allocated into three dietary treatments: control diet (CON), diet with 8% wheat gluten (WG) and diet with 8% OG with six pens/treatment. Body weight (BW) (21 and 35 days) and average daily gain (ADG) (1-21 days and 22-35 days) decreased (p < .05) and feed conversion ratio (FCR) (1-21 days and 22-35 days) increased (p < .05) in OG treatment. Feed intake (FI) decreased (p < .05) in WG and OG treatments during 22-35 days. However, FI was not influenced by dietary treatments during 1-21 days (p > .05). The OG-fed broilers had a lower faecal pH value (p < .05) and higher faecal moisture content (p < 05) at 14, 21, 28 and 35 days. Villus height, crypt depth and V/C value were not different (p > .05) among treatments at 21 and 35 days. Lipid peroxidation (LPO) (21 and 35 days) and malondialdehyde (MDA) (35 days) content in crop of OG treatment increased (p < .05). Oxidized glutathione (GSSG) (21 days), LPO (21 and 35 days) and MDA (21 and 35 days) content in ileum of OG treatment increased (p < .05). The reduced glutathione/oxidized glutathione (GSH/GSSG) (21 days) and (GSH) (35 days) in ileum of OG treatment decreased (p < .05). The present findings indicate that OG might be a stressor for broiler gut, which could induce oxidative stress both in crop and in ileum, and the diarrhoea as well. The growth performance of broiler was consequently depressed.