本试验旨在研究饲粮不同添加水平谷氨酰胺(Gln)对热应激肉鸡小肠组织结构和吸收能力的影响。选用1日龄科宝-500肉鸡240只,随机分为6个处理,每个处理4个重复,每个重复10只。Ⅰ组为对照组,饲喂玉米-豆粕型基础饲粮,Ⅱ、Ⅲ、Ⅳ、Ⅴ和Ⅵ组为试验组,分别饲喂在基础饲粮中添加0.4%、0.8%、1.2%、1.6%和2.0%谷氨酰胺的试验饲粮,试验时间为15~42日龄,共28 d。试验期间每天从09:00到17:00温度维持在(35±2) ℃,17:00至次日09:00温度维持在(30±2) ℃ ,鸡舍相对湿度控制在70%~80%。结果表明:1)饲粮中添加谷氨酰胺对29~42日龄肉鸡生长性能有显著影响(P<0.05),其中以1.2%谷氨酰胺的促生长效果最佳,但对15~28日龄肉鸡生长性能的影响不显著(P>0.05)。2)28日龄时,饲粮中添加0.8%~2.0%谷氨酰胺极显著提高了十二指肠和空肠绒毛高度(P<0.01),且2.0%谷氨酰胺组极显著高于其他组(P<0.01);添加0.4%、1.2%、2.0%谷氨酰胺显著或极显著提高了回肠绒毛高度(P<0.05或P<0.01),1.2%谷氨酰胺组极显著高于其他组(P<0.01)。42日龄时,饲粮中添加谷氨酰胺显著或极显著降低了十二指肠绒毛宽度和隐窝深度(P<0.05或P<0.01),但仅添加1.2%谷氨酰胺极显著提高了十二指肠绒毛高度(P<0.01);添加1.2%~2.0%谷氨酰胺显著或极显著提高了空肠和回肠绒毛高度、降低了绒毛宽度(P<0.05或P<0.01),且添加1.2%谷氨酰胺显著或极显著降低了空肠和回肠固有层厚度(P<0.05或P<0.01)。3)28日龄时,2.0%谷氨酰胺组小肠吸收能力极显著高于对照组(P<0.01),42日龄时,1.2%谷氨酰胺组小肠吸收能力显著高于对照组(P<0.05)。由此可见,饲粮中添加谷氨酰胺可改善热应激肉鸡小肠组织结构,并提高小肠吸收能力,综合考虑可知前期(15~28日龄)添加2.0%较好,后期(29~42日龄)添加1.2%较好。
The experiment was conducted to study the effects of dietary glutamine (Gln) on small intestinal structure and absorption in broilers suffered from heat stress. Two hundred and forty Cobb-500 one-day-old broilers were randomly selected and divided into 6 treatments with 4 replicates in each treatment and 10 chicks in each replicate. The broilers in group Ⅰ(control group) were fed a basal diet, and those in groups Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ were fed the basal diet supplemented with 0.4%, 0.8%, 1.2%, 1.6% and 2.0% glutamine, respectively. The experiment lasted for four weeks (days 15 to 42). During the experimental period, the temperature was maintained at (35±2) ℃ from 09:00 to 17:00, and was maintained at (30±2) ℃ from 17:00 to 09:00 of the next day. The relative humidity of the chicken house was controlled between 70% and 80%. The results showed as follows: 1) the supplementation of Gln in diets significantly influenced growth performance of broilers aged from 29 to 42 days (P<0.05), in which the supplementation of 1.2% Gln was the best, but there was no significant difference among all groups during 15 to 28 days (P>0.05). 2) At 28 days of age, the supplementation of Gln from 0.8% to 2.0% in diets significantly increased the villus height of duodenum and jejunum of broilers (P<0.05 or P<0.01), and 2.0% Gln group was significantly higher than the other groups (P<0.01). The supplementation of 0.4%, 1.2% and 2.0% Gln in diets significantly increased the villus height of ileum of broilers (P<0.05 or P<0.01), and 1.2% Gln group was significantly higher than the other groups (P<0.01). At 42 days of age, the supplementation of Gln in diets significantly decreased the villus width and crypt depth of duodenum of broilers (P<0.05 or P<0.01); the supplementation of 1.2% Gln in diets significantly increased the villus height of duodenum (P<0.01); the supplementation of 1.2%, 1.6% and 2.0% Gln in diets significantly increased the villus height and decreased the villus width (P<0.05 or P<0.01); and the supplementation of 1.2% Gln in diets significantly decreased the thickness of lamina propria of jejunum and ileum (P<0.05 or P<0.01). 3) The small intestinal absorption was significantly increased when the supplemental level of Gln was 2.0% at 28 days of age (P<0.01) and 1.2% at 42 days of age (P<0.05). In conclusion, dietary glutamine can improve the small intestinal structure and absorption in broilers suffered from heat stress, and the suitable level in diets is 2.0% from 15 to 28 days of age and 1.2% from 29 to 42 days of age.
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