锌对凡纳滨对虾生长、非特异性免疫指标、抗病力及肠道菌群结构的影响

Effects of dietary zinc on growth, serum non-specific immune indexes, disease resistance and intestinal flora structure in juvenile Litopenaeus vannamei

摘要:

为研究不同锌水平对凡纳滨对虾生长、非特异性免疫指标、抗病力以及肠道菌群结构的影响，实验以ZnSO₄·7H₂O作为锌源，在对虾基础饲料中分别添加0(对照组)、20、40、60、80、100、150 mg/kg有效锌配制成7种等氮等脂饲料，分别投喂初始体质量为(0.45±0.01) g的健康凡纳滨对虾幼虾8 周。结果显示：① 随着饲料中锌水平的提高，对虾增重率(WGR)、特定生长率(SGR)、存活率(SR)和蛋白质效率(PER)呈先上升后下降的趋势，饲料系数(FCR)呈先下降后上升的趋势。其中60 mg/kg组WGR和SGR均显著高于对照组；80 mg/kg组FCR最低，PER和SR最高，均显著优于对照组。② 80~150 mg/kg组虾体粗脂肪含量显著高于对照组；40~80 mg/kg组虾体粗灰分含量显著高于对照组。③ 40~150 mg/kg组对虾血清总蛋白(TP)、总胆固醇(TC)及甘油三酯(TG)含量均显著高于对照组。④ 饲料中添加锌提高了血清超氧化物歧化酶(SOD)、酚氧化酶(PO)、碱性磷酸酶(AKP)和酸性磷酸酶(ACP)活性及总抗氧化能力(T-AOC)，同时显著降低了血清中的丙二醛(MDA)含量，表明锌可改善凡纳滨对虾的非特异性免疫功能。⑤ 在人工急性感染哈维氏弧菌的实验中，随着锌水平的提高，对虾存活率呈先上升后下降的趋势，锌添加组存活率均显著高于对照组，且80 mg/kg组存活率最高，抗病力最强。⑥ 在对虾肠道物种多样性分析中，40和100 mg/kg组对虾肠道有效OTU数目显著高于对照组。随着锌水平的增加，Ace指数和Chao1指数均显著提高，而Shannon指数和Simpson指数无显著变化。研究表明，在本实验条件下，添加适宜水平的锌可促进凡纳滨对虾幼虾的生长、提高抗病力；当饲料中缺乏锌时，对虾的生长和抗病力较差；而过量的锌在一定程度上抑制了对虾的生长，但未出现不良病症。以增重率作为评价指标，饲料中添加94.46 mg/kg锌可显著改善凡纳滨对虾幼虾的生长；以抗病力作为评价依据，凡纳滨对虾幼虾饲料中锌的最适添加量为80 mg/kg。

关键词:凡纳滨对虾;锌;生长;非特异性免疫;抗病力;肠道菌群

Abstract:

The trial was conducted to study the effects of dietary zinc (Zn) on growth, non-specific immune indexes, disease resistance and intestinal flora structure in juvenile Litopenaeus vannamei. Zinc sulfate heptahydrate (ZnSO₄·7H₂O) was used as the Zn source in this experiment. The healthy prawns [initial body weight (0.45±0.01) g] were fed diets (isonitrogenous and isolipid) containing available Zn levels (i.e., 0, 20, 40, 60, 80, 100, and 150 mg/kg) for 8 weeks, respectively. The results showed that: ① The weight gain rate (WGR) and specific growth rate (SGR) in the 60 mg/kg group were significantly higher than those in the control group, and the best feed conversion rate (FCR), the optimal protein efficiency ratio (PER) and survival rate (SR) were found in 80 mg/kg group.② The crude lipid (CL) contents in 80-150 mg/kg groups were significantly higher than that in control group, and the contents of crude ash (CA) in 40-80 mg/kg groups were significantly higher than that in control group.③ The contents of serum total protein (TP), total cholesterol (TC) and triglyceride (TG) in Zn supplemented groups were significantly higher than those in control group. ④ Dietary Zn supplement increased the activities of serum superoxide dismutase (SOD), phenol oxidase (PO), alkaline phosphatase (AKP) and acid phosphatase (ACP) and total antioxidant capacity (T-AOC), and significantly decreased the content of malondialdehyde (MDA) in serum, indicating that Zn could improve the non-specific immunity of L. vannamei.⑤ In the experiment of artificial acute infection with Vibrio harveyi, the survival rate of shrimp increased firstly and then decreased with the increase of Zn levels. The survival rate in Zn supplemented group was significantly higher than that in control group, and the highest survival rate and disease resistance were found in 80 mg/kg group. ⑥ In the analysis of intestinal flora, the numbers of effective OTUs in 40 mg/kg and 100 mg/kg groups were significantly higher than that in control group. With the increase of dietary Zn, the Ace index and Chao1 index increased significantly, while the Shannon index and Simpson index had no significant changes. The results showed that an optimal level of Zn could promote the growth and improve the disease resistance of juvenile L. vannamei. The growth performance and disease resistance of L. vannamei were poor when Zn was deficient in diets, while excessive Zn level inhibited the growth of L. vannamei to a certain extent. Overall, based on the WGR, the growth performance of L. vannamei was significantly improved by supplementing 94.46 mg/kg Zn to the diets. Based on the evaluation of disease resistance, the optimal dietary Zn supplement of L. vannamei was 80 mg/kg.

Key words:Litopenaeus vannamei;zinc;growth;non-specific immunity;disease resistance;intestinal flora