饲料中添加壳寡糖和霉菌毒素吸附剂对凡纳滨对虾肠道黏膜形态及菌群结构的影响

实验旨在研究在饲料中分别或联合添加壳寡糖(chitosan oligosaccharide,COS)和霉菌毒素吸附剂(mycotoxins adsorbent)对凡纳滨对虾(Litopenaeus vannamei)肠道黏膜形态及菌群结构的影响。在基础饲料(对照组)中分别添加250 mg/kg COS、2500 mg/kg霉菌毒素吸附剂、250 mg COS+2500 mg/kg霉菌毒素吸附剂(组号为C0、C0.25、M2.5、C0.25+M2.5),制成4组等氮等能饲料,投喂初重(0.23±0.02)g的凡纳滨对虾8周。结果显示:COS与霉菌毒素吸附剂联合使用有助于改善肠道形态学指标,C0.25+M2.5组绒毛高显著大于C0、C0.25组(P0.05),绒毛宽显著大于M2.5组(P0.05),肌层厚度显著大于其他各组(P0.05)。高通量测序结果表明各组有效操作分类单元(Operational Taxonomic Unit,OTUs)数目无显著性差异(P0.05);C0.25+M2.5组Observed species指数、Shannon指数、PD值显著低于M2.5组(P0.05),但显著高于C0.25组(P0.05),与C0组无显著性差异(P0.05);肠道菌群主要为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes),C0.25+M2.5组变形菌门细菌含量最低且厚壁菌门细菌含量最高,各组拟杆菌门细菌均升高,C0组含量最低。在属水平上,弧菌属(Vibrio)、假交替单胞菌属(Pseudoalteromonas)、Spongiimonas、发光杆菌属(Photobacterium)以及Candidatus Bacilloplasma占主要优势,C0.25+M2.5组弧菌属、发光杆菌属细菌含量均有效减少;C0.25+M2.5组发光杆菌属细菌含量最低,假交替单胞菌属细菌含量最高。250 mg/kg COS和2500 mg/kg霉菌毒素吸附剂联合添加对菌群丰富度无显著影响,但优化了肠道形态学指标及肠道菌群结构,提升了肠道健康,效果优于单一添加组。

Effect of chitosan oligosaccharide and mycotoxin adsorbents on intestinal mucosa structure and gut flora of Litopenaeus vannamei

A 56-day feed trial was carried out to investigate the effects of chitosan oligosaccharide (COS) and/or mycotoxin adsorbent on the intestinal mucosa structure and gut flora of Litopenaeus vannamei. Four isonitrogenous and homoenergetic diets were prepared on the basal diet by adding 0 mg/kg (COS or mycotoxin adsorbent), 250 mg/kg COS, 2500 mg/kg mycotoxin adsorbent, 250 mg/kg COS+2500 mg/kg mycotoxin adsorbent, and named as C0, C0.25, M2.5 and C0.25+M2.5, respectively. The Litopenaeus vannamei with an initial weight of 0.23±0.02 g were randomly assigned into 4 groups. The results showed as follows:the combined use of COS and mycotoxin adsorbent helped improve the index of intestinal morphology, group C0.25+M2.5 showed significant difference (P<0.05) about the intestinal villus length with group C0, C0.25, and showed significant difference (P<0.05) about the intestinal width with group M2.5, moreover, the thickness of muscle layer in this group was significantly higher than others (P<0.05). There was no significant difference (P>0.05) about effective OTUs (Operational taxonomic unit) among groups; index of Observed species and Shannon index and PD (Phylogenetic diversity whole tree) value in group C0.25+M2.5 were significantly lower (P<0.05) than those of group M2.5 and remarkably higher than group C0.25, but showed no significant difference (P>0.05) with group C0. At the phylum level, microbial floras detected in this experiment mainly belonged to Proteobacteria, Firmicutes or Bacteroidetes, group C0.25+M2.5 showed the minimum of Proteobacteria and the maximum of Firmicutes, group C0 showed the minimum of Bacteroidetes. At the level of genus, species mainly detected were Vibrio, Pseudoalteromonas, Spongiimonas, Photobacterium and Candidatus Bacilloplasma. Vibrio or Photobacterium in group C0.25+M2.5 were lower than that of control group. Group C0.25+M2.5 showed the lowest content of Photobacterium and the highest content of Pseudoalteromonas. It can be concluded that adding COS and mycotoxin adsorbent in diets had no effect of on microbial floras, nevertheless, optimized the index of intestinal morphology and the structure of gut flora, but can promoted intestinal health, and is better than a single adding groups.