This study aimed to determine the effects of fructooligosaccharide ( FOS ) on immune response of blunt snout bream ( Megalobrama amblycephala) under high ammonia stress. A total of 360 fish were randomly distributed into three groups (each with four replicates) and were fed three levels of FOS (0, 0. 4% and 0. 8%) for 8 weeks. After the feeding trial, 24 fish per tank were exposed to ammonia at 10 mg/L. From the results, we found that Glutamic Pyruvic Transami-nase (GPT) levels of fish fed 0. 4% FOS were all significantly lower than that of the other groups at 0h and 24 h. After stress, Plasma acid phosphatase (ACP), complement 3 (C3), complement 4 (C4) and phenoloxidase (PO) activities all increased significantly with the maximum levels being attained at 3, 24, 12 and12 h, respectively. Thereafter, these parameters all decreased significantly. In addition, fish fed 0. 4% FOS showed higher C3 , C4 and PO compared to that of control group before stress. Whereas, only the C3 of fish fed 0. 4% FOS showed higher than that of control group at 3 h af-ter stress. There was no significant difference at other times and there was no significant interaction between the FOS levels and the time. The results indicated that the supplementation of 0. 4% FOS could increase the non-specific immunity of blunt snout bream, and enhance its resistance to high ammonia stress.%为研究氨氮应激条件下果寡糖对团头鲂( Megalobrama amblycephala)非特异免疫指标的影响,试验选择360尾初重为13．5 g的团头鲂随机分为3组,每组4个重复,每缸30尾鱼,对照组投喂基础日粮,试验组分别投喂果寡糖( FOS)添加量为0．4%和0．8%的日粮,饲养8周,养殖试验结束后,用10 mg/L的NH4 Cl对24尾鱼进行氨氮应激试验。试验结果显示,氨氮应激前,0．4% FOS组的血液谷丙转氨酶( GPT)活性显著低于对照组和0．8% FOS组,在氨氮应激后,0．4% FOS 组的 GOT 活性有降低的趋势,但仅在24 h 时显著低于0．8%组,0．8%组和对照组之间并无显著差异；血清酸性磷酸酶、补体3(C3)、补体4(C4)、酚氧化酶都出现先升高后降低的趋势,分别在应激后的3、24、12、12 h达到最大值。此外,应激前0．4% FOS组补体C3、 C4、酚氧化酶的活性都显著高于对照组,应激后0．4%FOS组C3在3 h处显著高于对照组,但是在其它时间点各组差异并不显著,果寡糖添加水平和采样时间对这些免疫指标都无显著的交互作用。结果表明饲料中添加0．4%的果寡糖能够提高团头鲂的免疫力指标活性,提高了团头鲂抗氨氮应激的能力。
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