纤维寡糖和益生菌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

Effects of Probiotics and Cello-Oligosaccharide on Nutrient Digestion,mRNA Expression of Intestinal Mucosa Amino Acid Transporters and Nitrogen Emission of Broilers under Heat Stress

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 ceUo-oligosaccharide （COS） on nutrient digestion, mRNA expression of intestinal mucosa amino acid transporters and nitrogen e- mission 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 exper- iment 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 sig- nificantly 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 ami- no 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 low- ered （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 nitro- gen excretion rate in HS＋SYN group were significantly reduced （P〈0.05）, while nitrogen retention was sig- nificantly 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.