水解单宁对珍珠龙胆石斑鱼生长性能、抗氧化能力、肠道组织结构与菌群多样性的影响

Effects of Hydrolyzable Tannins on Growth Performance,Antioxidant Capacity,Intestinal Morphology and Bacterial Diversity of Pearl Gentian Grouper(Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀)

本试验旨在研究水解单宁对珍珠龙胆石斑鱼(Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀)生长性能、抗氧化能力、肠道组织结构与菌群多样性的影响。选取600尾初始体重为(21.43±1.31) g的珍珠龙胆石斑鱼,随机分为5组,每组3个重复,每个重复40尾。在基础饲料配方的基础上分别以0(F0组,作为对照组)、0.05%(F1组)、0.10%(F2组)、0.15%(F3组)和0.20%(F4组)的水解单宁替代等量微晶纤维素,配制5种试验饲料,进行为期60 d的养殖试验。结果表明:F2组的增重率(WGR)和特定生长率(SGR)显著高于F0组(P<0.05),饲料系数(FCR)则显著低于F0组(P<0.05)。肥满度(CF)和存活率(SR)各组之间均无显著差异(P>0.05)。与F0组相比,F2和F3组血清和肝脏碱性磷酸酶(AKP)、酸性磷酸酶(ACP)和超氧化物歧化酶(SOD)活性以及肝脏过氧化氢酶(CAT)、锰超氧化物歧化酶(Mn-SOD)和谷胱甘肽过氧化物酶(GPx)的mRNA相对表达量显著升高(P<0.05)。与F0组相比,F1、F2、F3组的肠道绒毛高度显著增加(P<0.05),F3组的肌层厚度显著增加(P<0.05)。Illumina MiSeq测序结果显示,添加水解单宁的各试验组肠道菌群的Shannon指数和Chao1指数均高于F0组。从门水平看,各组肠道菌群中优势菌门均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)。与F0组相比,各试验组肠道菌群中变形菌门的比例降低,放线菌门、拟杆菌门和厚壁菌门的比例增加。主坐标分析和UPGMA聚类分析发现,F2和F3组的微生物群落较为接近,而与F0组差别较大。综上可知,饲料中添加0.10%~0.15%的水解单宁可提高珍珠龙胆石斑鱼的生长性能,增强鱼体免疫及抗氧化能力,改善肠道组织结构,优化肠道菌群结构。以WGR为评价指标,通过回归方程确定珍珠龙胆石斑鱼饲料中水解单宁的适宜添加量为0.10%。

The aim of this study was to investigate the effects of hydrolyzable tannins(HTs)on growth performance,antioxidant capacity,intestinal morphology and bacterial diversity of pearl gentian grouper(Epinephelus lanceolatus♂×Epinephelus fuscoguttatus♀).A total of 600 pearl gentian groupers with an initial body weight of(21.43±1.31)g were randomly divided into 5 groups with 3 replicates per group and 40 fish per replicate.HTs was added to a basal diet by substituting for the same level of microcrystalline cellulose at the levels of 0(F0 group,as control group),0.05%(F1 group),0.10%(F2 group),0.15%(F3 group)and20%(F4 group),respectively.The experiment lasted for 60 days.The results showed that the weight gain rate(WGR)and specific growth rate(SGR)in F2 group were significantly higher than those in F0 group(P<0.05),and the feed conversion rate(FCR)in F2 group was significantly lower than that in F0 group(P<0.05).No significant differences were found in condition factor(CF)and survival rate(SR)among groups(P>0.05).Compared with the F0 group,the activities of alkaline phosphatase(AKP),acid phosphatase(ACP)and superoxide dismutase(SOD)and the mRNA relative expression levels of catalase(CAT),manganese superoxide dismutase(Mn-SOD)and glutathione peroxidase(GPx)in F2 and F3 groups were significantly increased(P< 0.05).The intestinal villus height in F1,F2 and F3 groups and the intestinal muscle thickness in F3 group were significantly higher than those of F0 group(P <0.05).The Illumina MiSeq sequence assays showed that the Shannon index and Chao1 index of intestinal bacteria in experimental groups were higher than those in F0 group.The dominant species at the phylum level in all groups mainly included Proteobacteria,Actinobacteria,Bacteroidetes and Firmicutes.Compared with the F0 group,the proportion of Proteobacteria was decreased,whereas the proportions of Cyanobacteria,Actinobacteria and Bacteroidetes were increased in experimental groups.The principal coordinates analysis(PCoA)and UPGMA cluster analysis showed that the bacteria community in F2 and F3 groups might be quite similar,but different with F0 group.In conclusion,this present study documents that dietary supplemented with 0.10% to 0.15% HTs promotes growth performance,antioxidant capacity,improves the intestinal morphology and microbial community structure of pearl gentian grouper.The appropriate supplemental level of HTs obtained by quadratic regression equation is 0.10% based on WGR as the evaluation index.