本试验旨在研究益生菌（PRO）和纤维寡糖（COS）对热应激肉鸡营养物质消化、肠黏膜氨基酸转运载体mRNA表达和氮排放的影响。将900羽21日龄罗斯（Ross）308肉鸡分为5个组：热中性（TN）组、热应激（HS）组、益生菌（HS+0.15%PRO）组、纤维寡糖（HS+0.15%COS）组、合生素（HS+SYN，SYN=0.15%PRO+0.15%COS）组。热中性组鸡舍温度22℃；其余各组鸡舍为循环热应激，温度08：00-18：00为33℃，18：00-次日08：00为22℃。饲养试验期为21 d。结果如下：1）与热中性组相比，热应激组肉鸡平均日增重和平均日采食量分别显著降低10.65%（P<0.05）和8.04%（P<0.05），单独添加益生素或者纤维寡糖对肉鸡平均日增重、平均日采食量和料重比均无显著影响（P>0.05）；热应激组粗蛋白质和粗纤维表观消化率显著下降（P<0.05）；热应激组氮摄入量和氮沉积量显著降低（P<0.05），氮排泄量和排泄率及排泄物氨态氮和尿酸含量显著提高（P<0.05）；热应激组排泄物脲酶活性和鸡舍氨气浓度显著提高（P<0.05）；热应激组肠黏膜基础氨基酸运载体（rBAT）、y⁺L氨基酸运载体-2（y⁺LAT2）、阳离子氨基酸运载体-1（CAT1）和阳离子氨基酸运载体-4（CAT4）mRNA表达量显著降低（P<0.05）。2）与热应激组相比，益生菌组和纤维寡糖组粗蛋白质表观消化率显著升高（P<0.05），氮排泄量和氮排泄率显著降低（P<0.05），氮沉积量显著升高（P<0.05）；益生菌组排泄物氨态氮含量显著降低（P<0.05）；纤维寡糖组鸡舍氨气浓度、排泄物脲酶活性显著降低（P<0.05）。3）与热应激组相比，合生素组粗蛋白质和粗纤维表观消化率显著升高（P<0.05），氮排泄量、氮排泄率显著降低（P<0.05），氮沉积量显著升高（P<0.05），鸡舍氨气浓度、排泄物氨态氮含量和脲酶活性显著降低（P<0.05），肠黏膜rBAT mRNA表达量显著升高（P<0.05）。结果提示，热应激使肉鸡营养物质消化率下降和氮排放升高，益生菌和纤维寡糖不同程度地改善了热应激引起的上述不良影响，两者组合添加效果优于单独添加。

This experiment was conducted to study the effects of probiotics (PRO) and cello-oligosaccharide (COS) on nutrient digestion, mRNA expression of intestinal mucosa amino acid transporters and nitrogen emission of broilers under heat stress. Nine hundred 21-day-old Ross 308 broilers were randomly allocated to 5 groups: thermoneutralzone (HN) group, heat stress (HS) group, probiotics (HS+0.15%PRO) group, cello-oligosaccharide (HS+0.15%COS) group and synbiotics (HS+SYN,SYN=0.15%PRO+0.15%COS) group. Birds were either raised in a thermoneutral zone (22℃) in HN group, and the others were subjected to cyclic heat stress by exposing to 33℃ from 08:00 to 18:00 and 22℃ from 18:00 to next day 08:00. Raising experiment period was 21 days. The results showed as follows: 1) compared with birds kept in HN group, average daily gain and average daily feed intake of broilers subjected to heat stress were significantly reduced 10.65% (P<0.05) and 8.04% (P<0.05), respectively. Average daily gain, average daily feed intake and feed to gain ratio of broilers subjected to heat stress with diet added probiotics or cello-oligosaccharide individually were not significantly different (P>0.05). Apparent digestibility of crude protein and crude fiber in HS group was significantly decreased (P<0.05), nitrogen intake and nitrogen retention were significantly decreased (P<0.05), nitrogen excretion and nitrogen excretion rate were significantly increased (P<0.05), ammonia nitrogen, uric acid contents in excreta and ammonia concentration in chicken house were significantly increased (P<0.05), the activity of urease in excreta was significantly increased (P<0.05), and mRNA expression of the basic amino acid transporter (rBAT), y⁺L amino acid transporter-2 (y⁺LAT2), cationic amino acid transporter-1 (CAT1) and cationic amino acid transporter-4 (CAT4) in intestinal mucosa was significantly down-regulated (P<0.05). 2) Compared with HS group, apparent digestibility of crude protein was significantly increased in HS+PRO and HS+COS groups (P<0.05), nitrogen excretion and nitrogen excretion rate in HS+PRO and HS+COS groups were significantly reduced (P<0.05), while nitrogen retention was significantly increased (P<0.05). Compared with HS group, excreta ammonia nitrogen content in HS+PRO group was significantly lowered (P<0.05), and ammonia concentration in chicken house and activity of urease in excreta of HS+COS group were significantly reduced (P<0.05). 3) As compared with HS group, apparent digestibility of crude protein and crude fiber were significantly increased (P<0.05) in HS+SYN group. Nitrogen excretion and nitrogen excretion rate in HS+SYN group were significantly reduced (P<0.05), while nitrogen retention was significantly increased (P<0.05). Ammonia nitrogen concentration in chicken house, excreta ammonia nitrogen content and urease activity of HS+SYN group were significantly reduced (P<0.05). and mRNA expression of rBAT in intestinal mucosa in HS+SYN group was significantly up-regulated (P<0.05). The results indicate that heat stress decrease nutrient digestion and increase nitrogen emission of broilers, and dietary addition of probiotics and cello-oligosaccharide are effective in partially ameliorating these changes. The combination of probiotics and cello-oligosaccharide is superior to individually addition.