脂肪和蛋白质营养对工业化养殖大西洋鲑相关代谢酶和生长基因表达的影响

为探究主要脂肪和蛋白质水平对工业化养殖大西洋鲑(Salmo salar)成鱼脂肪相关代谢酶和生长相关基因表达的影响,本实验采用3×2双因素随机实验设计,设置3个脂肪水平:18%、21%、24%(分别以F18、F21、F24表示),2个蛋白质水平:38%、48%(分别以P38、P48表示)。组合为6个实验处理组,每组3个重复,每重复40尾鱼。实验在室内封闭循环水养殖系统中进行,实验鱼初始体重(650.0±45.50)g,实验期56 d。结果表明:(1)工业化养殖实验鱼的脂肪需求较国外深海网箱养殖明显降低,蛋白质需求相近。P48F21组增重率显著最佳,较其他各组提高22.23%~125.86%(P0.05);P48F24组饲料系数显著最低,较其他各组降低16.24%~30.00%(P0.05)。(2)单因素高脂肪显著提高肝体比(P0.05),高蛋白极显著降低肥满度(P0.01);P48F24组肝体比较其他各组显著提高10.92%~28.16%(P0.05),P48F18组肥满度较其他各组显著降低10.24%~12.31%(P0.05);并创新提出了600~900 g大西洋鲑形体营养调控初步方案。(3)单因素高、中脂肪显著提高肝脂肪分解酶(HL、LPL和总酯酶)活力,高蛋白显著提高LPL和总酯酶活力;P48F21和P48F24组饲粮显著提高肝脂肪分解酶活力,其中LPL活力比P38F18组分别提高46.51%、48.84%(P0.05)。实验处理主要对肝脂肪分解酶产生作用,显现了两组优良饲粮改善生长性能的脂肪生理代谢机制。(4)单因素中脂肪极显著增加肌肉和肝IGF-I基因表达量(P0.01);高蛋白极显著增加肌肉GH、IGF-I及肝IGF-I基因表达量(P0.01);GHR基因表达量,随脂肪或蛋白水平升高均有显著下降特征(P0.05)。P48F21和P48F24组试鱼肌肉GH、IGF-I及肝IGF-I基因表达量显著提高(P0.05),肌肉和肝GHR基因表达量显著降低(P0.05)。初步的新发现是,GH和IGF-I与GHR存在相互制约的负相关内在调控关系,以自身控制鱼类生长和生殖活动处于相对稳定和可控状态下。本研究初步确定,P48F21和P48F24组是工业化养殖大西洋鲑成鱼的主要营养素优良组合饲粮,其中以显著降低脂肪水平和饲料成本的P48F21组合饲粮更佳。

Effects of dietary fat and protein nutrition on fat metabolic enzymes and growth-associated gene expression of Atlantic salmon (Salmo salar) in the recirculating aquaculture system

Salmo salar is one of the most important aquaculture species in the world, cultured in a cage culture system, which was introduced to China in 2010 and in recirculating aquaculture system (RAS). In order to inves-tigate the effects of dietary fat and protein levels on fat metabolic enzymes and growth associated gene expression of S. salar in RAS, a 3×2 (three fat levels: 18%, 21%, and 24%; two protein levels: 38% and 48%, represented by F18, F21, F24, P38, and P48, respectively) random two-factor animal trial was conducted for 56 days. The trial included six treatments with triplicate groups of 40 trial fishes (650.00±45.50) g. Results showed that: (1) The fat requirement of S. salar was lower in RAS than in cage culture system, and the requirement of protein was equal between the two systems. The weight gain rate (WGR) was significantly higher in P48F21, by 22.23%–125.86%, than that in other groups (P<0.05), while the feed conversion rate (FCR) was significantly lower in P48F24, by 16.24%–30.00% than that in other groups (P<0.05). (2) High fat level significantly increased hepatosomatic index (HSI) (P<0.05), while high protein level decreased condition factor (CF) very significantly (P<0.01). The HSI was significantly higher in P48F24 group than in other groups, by 10.92%–28.16% (P<0.05), while the CF was sig-nificantly lower than that in other groups, by 10.24%–12.31%. The study proposed the primary nutrition project that can control the shape of S. salar to 600–900 g by weight. (3) High and medium fat levels significantly (P<0.05) increased the activity of lipoprotein lipase (LPL), hepatic lipase (HL), and total esterase, while high protein level significantly (P<0.05) increased the activity of LPL and total esterase. The activities of LPL, HL, and total esterase in P48F21 and P48F24 groups were significantly higher than those in other groups (P<0.05), and especially the activity of LPL in the two groups was higher than that in the P38F18 group, in which the activity of LPL was the lowest (P<0.05). We also found a significant negative correlation between protein level and the ac-tivity of fatty acid synthase (FAS) (P<0.05). (4) Medium fat level increased the expression of IGF-I gene in mus-cle and liver extremely significantly (P<0.01), while high protein level increased the expression of GH and IGF-I genes in muscle and IGF-I gene in liver extremely significantly (P<0.01). The expression of GHR decreased sig-nificantly with the increase in fat or protein level (P<0.05). The expressions of GH and IGF-I genes in muscle and IGF-I gene in liver in P48F21 and P48F24 groups were significantly higher than those in other groups (P<0.05), while the expression of GHR in muscle and liver was lower than that in other groups (P<0.05). We found negative correlations among GH, IGF-I, and GHR, which could control the growth and reproductive activities in appropri-ate ranges. In conclusion, P48F21 and P48F24 groups had obvious promoting effects on growth performance and growth-associated gene expression in S. salar, while P48F21 group was better in the use of fat and saving of costs.