脂肪营养对封闭循环水养殖道氏虹鳟生长、相关代谢酶及基因表达的影响

摘要

为探讨饲料脂肪营养对封闭循环水养殖道氏虹鳟(Oncorhynchus mykiss)生长、脂肪代谢及相关酶基因表达的影响,作者采用单因素设计,即4个脂肪水平——12％、15％、18％、21％(以Ⅰ、Ⅱ、Ⅲ、Ⅳ组表示),共4个处理组,每处理3重复,每重复25尾鱼.试验鱼为初始体质量(333.25±20.71)g的道氏虹鳟幼鱼,试验期77 d.结果表明,与后3组相比,Ⅰ组试验鱼增质量率显著提高17.20％～33.17％,Ⅰ和Ⅱ组饲料系数显著低于Ⅲ和Ⅳ组6.20％～20.56％(P＜0.05);脂肪合成酶类FAS活力随饲料脂肪水平升高而降低,脂肪分解酶类LPL、HL及L-CPT Ⅰ活力变化特征与之相反(P＜0.05).其中,Ⅰ组FAS活力显著高于Ⅲ、Ⅳ组7.5％、8.7％;L-CPT Ⅰ活力显著低于后3组13.08％～16.35％;Ⅳ组LPL活力显著或极显著高于前3组18.8％～44.7％(P＜0.05或P＜0.01);Ⅰ组肝脏FAS的mRNA表达量比后3组显著高48.29％～55.15％(P＜0.05);LPL呈相反特征,Ⅳ组显著高于前3组36.72％～113.59％(P＜0.05或P＜0.01);Ⅰ组肌肉FAS mRNA表达量显著高于Ⅳ组66.82％(P＜0.05);LPL表达丰度随脂肪水平升高先下降后显著上升(P＜0.05).该结果特征与肝脏中该两种酶活力变化具有同步性.研究发现,随饲料脂肪水平变化,肌肉FAS mRNA表达量变化比肝脏更明显且规律性更强,而肝脏LPL mRNA表达量变化较肌肉更明显.本试验初步确定,在封闭循环水养殖模式下,330 g左右道氏虹鳟饲料蛋白水平在45％时,脂肪水平以不超过12％为宜.%The aim of this trial was to evaluate the effects of dietary lipid levels on growth performance,fat metabolism,and gene mRNA expression of rainbow trout (Oncorhynchus mykiss) in a recirculating aquaculture system (RAS).Four isonitrogenous diets containing 45％ crude protein with increasing dietary lipid levels of 12％,15％,18％,and 21％ (denoted as groups Ⅰ,Ⅱ,Ⅲ,and Ⅳ) were fed to satiety to triplicate groups of 25 fishes (weighing 333.25 ± 20.71 g) for 77 days.Results are described as follows:First,the growth performance of fish fed group Ⅰ diet was optimal due to the highest weight gain (77.41％) and the lowest feed conversion rate (1.16) (P ＜0.05 or P ＜ 0.01);Second,fatty acid synthetase (FAS) activity was decreased with increasing dietary fat content,whereas the activities of lipolytic enzymes were increased.The FAS activity of fish fed group Ⅰ diet was significantly higher than those fed groups Ⅲ and Ⅳ diets by 7.5％ and 8.7％,respectively.The L-CPT Ⅰ activity of fish fed group Ⅰ diet was lower than that offish fed other diet groups by 13.08％-16.35％ (P ＜ 0.05).Meanwhile,the LPL activity of fish fed group Ⅳ diet was significantly highest (P ＜ 0.05).This result implies that fishes fed group Ⅰ diet improved their fat utilization rate by increasing fat synthesis and decreasing lipolysis to ensure the body's normal requirement for lipids and promote growth;Third,FAS mRNA expression in fish fed group Ⅰ diet was higher than that of fish fed other diet groups by 48.29％-55.15％ (P ＜ 0.05),whereas the changes in LPL showed an opposite pattern (P ＜ 0.05 or P ＜ 0.01).In the muscle,the FAS mRNA expression in fish fed group Ⅰ diet was higher than that of fish fed group Ⅳ diet by 66.82％ (P ＜ 0.05),and the expression of LPL was initially decreased and then increased with increasing dietary lipid levels.The preliminary finding was that FAS and LPL gene expression in the liver changed faster than that in the muscle with the increase in fat levels.Determined primarily,the Donaldsons rainbow trout (weighing about 330 g) could achieve healthy growth without excessive fat supply,and its fat nutrition requirement is no more than 12％ in RAS when the dietary protein level is 45％.