脱脂黄粉虫粉替代鱼粉对花鲈生长性能和肠道健康的影响

Effects of substituting fish meal with defatted yellow mealworm (Tenebrio molitor) on the growth and gut health of spotted seabass

中文关键词: 脱脂黄粉虫粉  鱼粉  替代  花鲈  生长性能  肠道健康

英文关键词: Defatted mealworm meal  Fish meal  Replacement  Lateolabrax maculatus  Growth performance  Intestinal health

中文摘要:

      为研究脱脂黄粉虫(Tenebrio molitor)粉替代鱼粉对花鲈(Lateolabrax maculatus)生长性能和肠道健康的影响，以花鲈幼鱼[初始体重为(2.83±0.02) g]为实验对象，配制鱼粉水平为30%的饲料作为对照组(FM)饲料，用脱脂黄粉虫粉(TM)分别替代对照组饲料中5% (5% TM)、10% (10% TM)、15% (15%TM)和20% (20% TM)的鱼粉，配制成5种等氮等脂的实验饲料，对实验花鲈进行为期 9周的摄食生长实验。结果显示，随着脱脂黄粉虫粉添加水平的增加，花鲈增重率、特定生长率和蛋白质沉积率均呈先升高后降低的趋势，5% TM组最高，显著高于20% TM组，但与FM、10% TM和15% TM组差异不显著。各组饲料效率、摄食率、存活率、肝体比、腹脂率以及全鱼体组成均无显著差异。脏体比随着替代水平的增加先升高后降低，20% TM组显著高于FM组和5% TM组。花鲈血清溶菌酶活性随脱脂黄粉虫粉替代比例的增加呈先升高后降低的趋势，5% TM组显著高于其他脱脂黄粉虫粉添加组。肠道组织观察发现，花鲈肠道的绒毛高度、绒毛宽度和肌层厚度随着脱脂黄粉虫粉替代水平的升高呈先升高后降低的趋势，5% TM组花鲈肠道的绒毛高度、绒毛宽度和肌层厚度达到最高，而20% TM组最低。随着替代水平的升高，花鲈肠道促炎因子IL-1β的相对表达量随脱脂黄粉虫粉替代水平的增加呈先降低后升高的趋势，5%~15% TM组显著低于FM组和20% TM组；抑炎因子IL-4的相对表达量呈先下降后上升的趋势，10% TM组具有最低值，而20% TM组具有最高值；肠道屏障相关基因(ZO-1和Ocln)的表达量呈先升高后降低的趋势，5% TM组的ZO-1和10% TM组的Ocln的表达量最高。各组微生物多样性指数无显著差异，但脱脂黄粉虫粉替代鱼粉改变了肠道有益菌和有害菌的相对丰度。与FM组相比，10% TM和15% TM组芽孢杆菌属(Bacillus)的相对丰度均显著增加，而5% TM和10% TM组邻单胞菌属(Plesiomonas)的相对丰度有下降趋势。综上所述，脱脂黄粉虫粉替代饲料中5%的鱼粉有利于花鲈肠道健康和生长；替代15%时不会对花鲈生长以及肠道健康产生负面影响；当脱脂黄粉虫粉替代比例超过20%时，不利于花鲈肠道健康，降低了其免疫能力，使其生长性能下降。根据二次回归模型计算结果，建议在淡水养殖时花鲈饲料中脱脂黄粉虫粉替代鱼粉水平不高于7.31%。

英文摘要:

      A 9-week feeding trial was performed to investigate the effects of substituting fish meal (FM) with defatted mealworm Tenebrio molitor meal (TM) on the growth, body composition, serum immune index, as well as histology, barrier functions, digestive enzymatic activities, and microbial communities of the intestine of spotted seabass (Lateolabrax maculatus). In this study, the basal diet was formulated to contain 30% FM, and five experimental diets were formulated by replacing FM with TM at different levels: 0 (TM 0), 5% (5% TM), 10% (10% TM), 15% (15% TM), and 20% (20% TM). Juvenile spotted seabass (2.83±0.02) g were randomly assigned to five treatments with three replicates and 20 fish per replicate. The results showed that the weight gain rate, specific growth rate, and protein productive value of spotted seabass first increased and then decreased with an increase in TM. Among the treatments, there were no difference in the feed efficiency, feeding rate, survival, hepatosomatic index, abdominal fat ratio, or body composition (P>0.05), but the viscerosomatic index was higher in the 5% TM treatment than that in the 20% TM treatment (P<0.05). The serum lysozyme activity was induced in the 5% TM treatment compared to that in other TM treatments (P>0.05). Intestinal histomorphology of spotted seabass was altered with increased dietary TM levels. Compared with the FM treatment, the intestinal villus width, villus height, and muscular thickness were increased significantly in the 5% TM treatment, while all three indices were decreased significantly in the 20% TM treatment (P<0.05). Meanwhile, the expression of the pro-inflammatory gene IL-1β was significantly down-regulated in 5%–15% TM treatments compared to that in the FM and 20% TM treatments (P<0.05). A similar pattern was observed in the expression of the anti-inflammatory gene IL-4. The transcripts of genes associated with barrier functions (ZO-1 and Ocln) were significantly up-regulated in the 5% TM treatment (P<0.05). However, the activity of digestive enzymes (protease and lipase) was not different among all treatments (P>0.05). Furthermore, the alteration of intestinal microbial communities was observed with increasing dietary TM levels. Higher genus abundance of Bacillus was observed in the TM treatments compared to that in the FM treatment (P<0.05), and the relative abundance of Plesiomonas tended to decrease in the 5% TM and 10% TM treatments. In conclusion, substituting fish meal with 5% TM can improve the growth and intestinal health of spotted seabass, while 15% TM had no negative effects on fish. However, excess dietary TM (20%) inhibits growth, causes histopathological damage, and alters the composition of intestinal microbial community in L. maculatus. According to the results of the quadratic regression model, the level of fishmeal substitution by TM in the diet of spotted seabass should not be greater than 7.31%.