以尼罗罗非鱼［体重(100.39±17.83) g］为实验对象，小麦基础饲料为对照，小麦基础饲料中分别添加不同水平的木聚糖酶(0.05%、0.10%、0.15%)作为实验饲料。每个处理设5个重复，每个重复放养40尾雄性尼罗罗非鱼。饱食投喂，饲养78 d后测定尼罗罗非鱼肠道细菌总量，并对需氧菌和厌氧菌进行鉴定，旨在研究木聚糖酶调控肠道菌群、促进尼罗罗非鱼生长的机理。结果表明，0.10%组和0.15%组前肠需氧菌数量显著低于对照组(P<0.05)，0.05%组、0.10%组和0.15%组中肠需氧菌数量显著低于对照组(P<0.05)。实验组后肠需氧菌数量均显著低于对照组(P<0.05)。0.15%组前肠厌氧菌数量比对照组、0.05%组和0.10%组分别降低76.85%(P<0.05)、75.62%(P<0.05)、75.83%(P<0.05)。0.10%组和0.15%组中肠厌氧菌数量显著低于对照组和0.05%组(P<0.05)。0.05%组、0.10%组和0.15%组后肠厌氧菌数量分别比对照组降低13.13%(P>0.05)、48.30%(P<0.05)、60.62%(P<0.05)。小麦基础饲料中添加木聚糖酶，主要影响需氧菌Ent.，Bac.和厌氧菌Bact.，Bif.，Lac.的组成比例。0.05%组、0.10%组和0.15%组前肠Ent.比例较对照组分别降低13.16%(P>0.05)、29.61%(P<0.05)、49.34%(P<0.05)。实验组前肠Bac.比例显著高于对照组(P<0.05)。0.10%组和0.15%组中肠、后肠Bac.比例显著高于对照组(P<0.05)。0.15%组前肠Lac.比例显著高于对照组和0.05%组(P<0.05)。对照组前肠Bact.比例显著高于0.10%组和0.15%组(P<0.05)。实验组中肠Bif.组成比例较对照组有显著提高(P<0.05)。0.15%组中肠Lac.比例显著高于对照组和0.05%组(P<0.05)。0.10%组和0.15%组中肠Bact.比例较对照组明显下降(P<0.05)。本研究认为，小麦基础饲料中添加木聚糖酶，可以调控尼罗罗非鱼肠道菌群，降低肠道致病菌Ent.和Bact.的组成比例，提高有益菌Bac.，Bif.和Lac.的组成比例。

The purpose of adding xylanase to wheat basal diet in this paper was to study the influences of xylanase on the quantity and composition of intestinal microflora, display the mechanism of xylanase promoting Oreochromis niloticus growth. Oreochromis niloticus were used as experiment objects in this study and their initial body weight was (100.39±17.83)g. Wheat basal diet was control. The tested diets were wheat basal diet added with different levels of xylanase (0.05%, 0.10%, and 0.15% respectively). Each treatment was devised with 5 repeats and each repeat had 40 male Oreochromis niloticus. The fish in floating cages were fed to satiation for 78 days. In this paper, we measured the amount of bacteria in intestinal of Oreochromis niloticus. Anaerobic bacteria were identified by BIOMERIEUX VITEKⅡ Automated Identification Systems and VITEKANA ID Kit. The results showed that the quantity and composition of intestinal microflora of Oreochromis niloticus were changed by dietary xylanase to wheat basal diets. The forgut quantity of aerobic bacteria of 0.10% and 0.15% xylanase groups were significantly lower than that of the control (P<0.05 respectively).The midgut quantity of aerobic bacteria of 0.05%, 0.10% and 0.15% xyanase groups were significantly lower than that of the control (P<0.05 respectively). The hindgut quantity of aerobic bacteria of the test groups were lower significantly than that of the control (P<0.05). The foregut quantity of anaerobic bacteria of 0.15% xylanase group was decreased by 76.85%, 75.62% and 75.83% compared with those of the control, 0.05% and 0.10% groups (P<0.05 respectively). The midgut quantity of anaerobic bacteria of 0.10% and 0.15% xylanase groups were lower significantly than those of the control and 0.05% xylanase group (P<0.05). The hindgut quantity of anaerobic bacteria of 0.05%, 0.10% and 0.15% xylanase groups were decreased by 13.13%, 48.30% and 60.62% compared with that of the control(P>0.05, P<0.05, P<0.05 respectively). The xylanase mainly influenced the proportion of Ent., Bac., Bact., Bif. and Lac.. The proportion of foregut Ent. of 0.05%, 0.10% and 0.15% xylanase groups were decreased by 13.16%, 29.61% and 49.34% compared with that of the control (P>0.05, P<0.05, P<0.05 respectively). The proportion of foregut Bac. of three test groups were significantly higher than that of the control (P<0.05). The proportion of Bac. in midgut and hindgut of 0.10% and 0.15% xylanase groups were higher than those of the controls (P<0.05). The proportion of foregut Lac. of 0.15% xylanase group was significantly higher than those of the control and 0.05% xylanase group (P<0.05 respectively). The proportion of foregut Bact. of the control was significantly higher than those of 0.10% and 0.15% groups(P<0.05 respectively). The proportion of midgut Bif. of test groups were increased significantly compared with that of the control(P<0.05). The proportion of midgut Lac. of 0.15% xylanase group was significantly higher than those of the control and 0.05% xylanase group(P<0.05). The proportion of midgut Bact. of 0.10% and 0.15% xylanase groups were decreased significantly compared with that of the control(P<0.05).

河南省重点科技攻关项目(092102210127); 河南省自然科学基金研究项目(200510476015); 河南省动物学重点学科资助项目