高植物蛋白饲料中添加硒对大菱鲆幼鱼肝肠健康的影响

Effects of Selenium Supplementation in High Plant Protein Diets on Liver and Intestinal Health of Juvenile Turbot

【目的】研究硒对摄食高植物蛋白饲料大菱鲆(Scophthalmus maximus L.)幼鱼肝肠健康的影响,为降低低鱼粉饲料对鱼体肝肠健康的不利影响提供依据。【方法】以初始体质量(30.79±0.22)g的大菱鲆为研究对象,以鱼粉质量分数55%的饲料组为正对照组(DP),以质量分数27.6%混合植物蛋白替代质量分数30%鱼粉为负对照组(DN),分别在低鱼粉中添加0.3(D1)、0.6(D2)、1.2(D3)、2.4(D4)、4.8(D5)mg/kg亚硒酸钠,以肝脏和肠道生理生化指标、肠道形态结构及肠道菌群结构等指标评价硒对大菱鲆幼鱼肝脏和肠道健康的影响。实验养殖周期52 d。【结果】1)与DP组相比,DN组显著降低大菱鲆肝脏和肠道总抗氧化能力(T-AOC)、总超氧化物歧化酶(SOD)和谷胱甘肽过氧化物(GSH-PX)酶活性(P<0.05);低鱼粉饲料中添加亚硒酸钠均可以不同程度提升上述所有指标,并降低丙二醛(MDA)含量(P<0.05)。2)与DP组相比,DN组显著提高了大菱鲆幼鱼肝脏肝糖原和脂肪酸合成酶(FAS)含量(P<0.05),而FAS含量则在D1-D5组显著低于DN组(P<0.05)。幼鱼肝脏SE-P含量在D2和D5组显著高于DN组(P<0.05)。3)0.3~1.2 mg/kg亚硒酸钠可抑制由低鱼粉引起的pat1、lzm和gst的mRNA表达水平的下调和前肠皱襞高度和黏膜厚度的降低,并可以显著提高肠道胰蛋白酶活性、脂肪酶活性和淀粉酶活性(P<0.05)。4)低鱼粉组肠道微生物组成的丰度和多样性显著降低,而亚硒酸钠组则可以明显改善这些不良现象,并可提升有益菌丰度,降低致病菌丰度。【结论】亚硒酸钠可缓解高植物蛋白饲料对大菱鲆造成的免疫下降、肠道组织结构破坏、消化功能下降及肠道菌群紊乱等不良影响。在低鱼粉饲料中亚硒酸钠的建议添加剂量为0.6~2.4 mg/kg。

【Objective】To reduce bad effect of the low fish meal diet on liver and intestine health of Scophthalmus maximus L.,the present study investigated the effects of dietary selenium on liver and intestinal health of turbot fed with high plant protein diet.【Method】With similar weight of about 30.79 g turbot were randomly divided into seven groups:DP,DN,D1,D2,D3,D4 and D5,respectively.Seven diets were consisted of a positive control diet with mass fraction 55%fish meal,a negative control diet was replaced with mass fraction 27.6%mixed plant protein instead of mass fraction 30%fish meal.The other five experimental diets which formulated by adding 0.3%,0.6%,1.2%,2.4%and 4.8%sodium selenite to the negative control diet respectively.The effects of selenium on liver and intestinal health of juvenile turbot which were based on liver and intestinal physiological and biochemical indexes,intestinal morphology and intestinal flora structure.The trial lasted for 52 days.【Result】The results showed as follows:(1)The sodium selenite supplementation alleviated the oxidative damage caused by the high plant protein diet on turbot,mainly by improving activities of total antioxidant capacity(T-AOC),total superoxide dismutase(SOD)and glutathion peroxidase(GSH-PX)in liver and intestine,reducing the content of malondialdehyde(MDA)(P<0.05).(2)Compared with DP group,the contents of liver glycogen and fatty acid synthetase(FAS)of torbot in DN group were significantly increased(P<0.05),while the contents of FAS in groups D1 to D5 were significantly lower than those in DN group(P<0.05).Whereas,the supplementation of 0.6 to 4.8 mg/kg sodium selenite significantly increased the SE-P content in liver(P<0.05).(3)Appropriate sodium selenite can inhibit the down-regulation of pat1,lzm and gst mRNA expression levels and the decrease of intestinal fold height and mucosal thickness caused by low fish meal,and can significantly improve intestinal trypsin activity,lipase activity and amylase activity(P<0.05).(4)Moreover,sodium selenite restored the decreased alpha-diversity index(Chao1,Ace)of intestinal flora induced by the high plant protein diet.Furthermore,sodium selenite reversed intestinal flora disturbance caused by the high plant protein diet,mainly by increasing the abundance of beneficial bacteria(Firmicutes and Bacteroidota).【Conclusion】In conclusion,sodium selenite mitigated the negative effects of high plant protein diet on the liver and intestinal health and intestinal health of torbot,and the recommended supplemental level of sodium selenite in the high plant protein diet was 0.6―2.4 mg/kg.