添加嗜酸乳杆菌对凡纳滨对虾生长、酶活性及相关酶mRNA表达的影响

本实验旨在研究饲料中添加嗜酸乳杆菌(Lactobacillus acidophilus)对凡纳滨对虾(Litopenaeus vannamei)幼虾生长、非特异性免疫酶活性、抗病力和相关酶m RNA表达的影响。选取840尾初始均重为(0.58±0.01)g的凡纳滨对虾幼虾为研究对象,分为7个处理,每个处理3个重复。投喂添加不同比例(0%,0.1%,0.2%,0.4%,0.6%,0.8%,1.0%)嗜酸乳杆菌的饲料,养殖期8周。结果显示:添加不同比例嗜酸乳杆菌对凡纳滨对虾的成活率无显著影响(P0.05)。增重率与特定生长率随添加量的增加呈先上升后下降的趋势,但均显著高于对照组(P0.05),在0.4%组达到最大值;当添加0.2%时,饲料系数最低,其他各组显著低于对照组(P0.05),而蛋白质效率的变化规律则与饲料系数相反。血清酚氧化物酶(phenoloxidase,PO)、碱性磷酸酶(alkaline phosphatase,AKP)和酸性磷酸酶(acid phosphatase,ACP)活性随添加量的增加先升高后降低,分别为0.4%、0.1%和0.2%时,达到最大值。过氧化氢酶(catalase,CAT)、溶菌酶(lysozyme,LZM)和超氧化物歧化酶(superoxide dismutase,SOD)活性,实验组均显著高于对照组(P0.05)。实验组过氧化氢酶(CAT)m RNA表达量和溶菌酶(LZM)m RNA表达量均显著高于对照组(P0.05)。哈维弧菌(Vibrio harveyi)攻毒96 h,对虾存活率随添加量的增加显著升高(P0.05)。以增重率(weight gain rate,WGR)为判断依据,根据折线模型得出,饲料中添加0.23%嗜酸乳杆菌可显著促进凡纳滨对虾生长,并提高非特异性免疫酶活性。

Effects of Lactobacillus acidophilus supplementation on the growth, enzyme activities, and mRNA expression of disease-resistance related enzymes of juvenile Litopenaeus vannamei

An 8-week feeding trial was carried out to investigate the effects of Lactobacillus acidophilus supplementation on the growth performance, nonspecific immunity-related enzyme activities, and disease resistance-related enzyme mRNA expression in juvenile Litopenaeus vannamei. A total of 840 L. vannamei, with initial average weight of 0.58±0.01 g, was randomly assigned to 7 groups in triplicates, with 40 individuals per replicate. Seven isonitrogenous and isolipid diets were supplemented with 0%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% Lactobacillus acidophilus in a basal diet, respectively. Following results were observed:nonsignificant difference was found in survival among all the groups (P>0.05). Weight gain rate (WGR) and specific growth rate (SGR) increased gradually as dietary L. acidophilus supplementation increased up to 0.4%, and then showed decline (P<0.05). The minimum feed conversion rate (FCR) was observed on feed supplementation with 0.2% L. acidophilus, which was significantly lower than that in the other groups (P<0.05), while protein efficiency rate (PER) showed the opposite trend. Serum phenoloxidase (PO), alkaline phosphatase (AKP), and acid phosphatase (ACP) activities increased gradually with increasing dietary L. acidophilus levels, and then gradually declined. The maximum values of PO, AKP, and ACP were found in the 0.4%, 0.1%, and 0.2% supplementation groups, respectively (P<0.05). Activities of serum catalase (CAT), lysozyme (LSZ), and superoxide dismutase (SOD) of all treatment groups were significantly higher than that of the control group (0%) (P<0.05). Gene expression levels of CAT and LZM in all treatment groups were significantly up-regulated when compared with the control group (P<0.05). At the end of the feeding trial, the shrimps were challenged by Vibrio harveyi for 96 h. Post-challenge survival rate increased with increasing dietary L. acidophilus supplementation (P<0.05). Based on the broken-line regression analysis of WGR, when feed was supplemented with 0.23% of L. acidophilus, growth and nonspecific immunity of juvenile Litopenaeus vannamei were found to significantly improve.