饲料赖氨酸水平对黄鳝幼鳝生长性能、生化指标、蛋白质代谢相关基因的影响

EFFECTS OF DIETARY LYSINE LEVELS ON GROWTH PERFORMANCE, BIOCHEMICAL INDEXES, AND PROTEIN METABOLISM RELATED GENES OF JUVENILE RICE FIELD EEL (MONOPTERUS ALBUS)

  • 摘要: 为探究黄鳝(Monopterus albus)幼鳝对赖氨酸的需求量。配制了6组赖氨酸实测值为2.31%、2.61%、2.91%、3.51%、4.71%和7.11%的等氮等能饲料, 饲喂初始体重为7.64±0.04 g幼鳝90d。结果表明: (1)随饲料赖氨酸水平的升高, 幼鳝增重率(WGR)、特定生长率(SGR)、蛋白质沉积率(PRR)、蛋白质效率(PER)先升高再下降, 饲料系数(FCR)先下降后上升; 3.51%水平显著提高了幼鳝WGR、SGR、PRR、PER, 降低了FCR (P<0.05)。3.51%水平显著提高幼鳝肝脏mTORS6K1IGF-1的相对表达量, 降低了eIF4E-BP2的相对表达量(P<0.05)。(2)随饲料赖氨酸水平的升高, 幼鳝肌肉粗蛋白质呈先升高后不变趋势, 粗脂肪呈先上升后下降趋势, 7.11%水平显著提高了幼鳝肌肉粗蛋白质、总氨基酸(TAA)、必需氨基酸(EAA)、非必需氨基酸(NEAA)含量(P<0.05), 3.51%水平显著提高了幼鳝肌肉粗脂肪含量、EAA/TAA、EAA/NEAA (P<0.05)。(3)随饲料赖氨酸水平的升高, 幼鳝血清总蛋白(TP)、白蛋白(ALB)呈升高趋势, 7.11%水平显著高于2.31%水平(P<0.05); 谷草转氨酶活性(GOT)及血氨(Sa)呈先下降后上升趋势, 溶菌酶(LZM)活性呈先上升后下降趋势; 3.51%水平Sa显著低于其余水平(P<0.05), 2.91%水平GOT显著低于2.31%水平(P<0.05), 4.71%水平LZM显著高于2.31%—2.91%水平(P<0.05)。(4)随饲料赖氨酸水平的升高, 幼鳝肝胰脏、前肠胰蛋白酶活性及前肠脂肪酶活性呈先升高后降低趋势, 2.91%—3.51%水平显著提高了幼鳝蛋白酶和脂肪酶活性(P<0.05)。综上, 饲料适宜赖氨酸水平能够提高幼鳝消化能力以及非特异性免疫能力, 通过促进GH/IGF及mTOR通路相关基因表达增强机体蛋白质沉积, 从而提高幼鳝生长性能。以WGR、SGR、FCR、PRR、PER为评价指标, 黄鳝幼鳝(7.64±0.04 g)的适宜赖氨酸需求量为3.38%—3.55% (占饲料蛋白质6.57%—6.90%)。

     

    Abstract: A 90d feeding trial was conducted to determine the dietary lysine requirement of juvenile rice field eel (Monopterus albus), with an initial weight of (7.64±0.04) g reared in indoor aerated tanks. Six isonitrogenous and isoenergetic practical diets were formulated with graded levels of lysine (2.31%, 2.61%, 2.91%, 3.51%, 4.71%, and 7.11% dry matter). The result showed that: (1) The weight gain rate (WGR), specific growth rate (SGR), protein retention rate (PRR), and protein efficiency ratio (PER) of M. albus increased firstly and then decreased with the increase of dietary lysine level, and the feed conversion ratio (FCR) decreased first and then increased. Conversely, the FCR decreased initially and then increased. A dietary lysine level of 3.59% significantly improved the WGR, SGR, PRR, and PER and reduced FCR (P<0.05). A level of 3.51% significantly increased the relative expression of mTOR, S6K1, and IGF-1 in the liver, while decreasing the relative expression of eIF4E-BP2 (P<0.05). (2) With the increase of dietary lysine level, the crude protein in the muscle of juvenile M. albus increased firstly and then plateaued, while crude fat increased firstly and then decreased. The 7.11% lysine level significantly increased the contents of crude protein, total amino acid (TAA), essential amino acid (EAA), and non-essential amino acid (NEAA) in muscle (P<0.05). The 3.51% level significantly increased the crude fat content, EAA/TAA, and EAA/NEAA (P<0.05). (3) With the increase of dietary lysine level, the serum total protein (TP) and albumin (ALB) showed an increasing trend, and the 7.11% level was significantly higher than the 2.31% level (P<0.05). Serum glutamic oxalacetic transaminase activity (GOT) and serum ammonia (Sa) decreased firstly and then increased, while lysozyme (LZM) activity increased firstly and then decreased. Sa at 3.51% was significantly lower than that at other levels (P<0.05). GOT at 2.91% was significantly lower than that at 2.31% (P<0.05), and LZM at 4.71% was significantly higher than the level between 2.31% and 2.91% (P<0.05). (4) The activity of trypsin in hepatopancreas and foregut, as well as lipase activity in foregut, increased firstly and then decreased with increasing dietary lysine levels. Levels between 2.91% and 3.51% significantly increased trypsin and lipase activity in juvenile M. albus (P<0.05). In summary, the appropriate dietary lysine level can improve the digestive ability and non-specific immunity, promote the expression of GH/IGF and mTOR pathway related genes, and enhance the protein deposition, thereby improving the growth performance of juvenile M. albus. The optimal lysine requirement of M. albus (7.64±0.04 g) is estimated to be between 3.38% and 3.55% (6.57% to 6.90% of feed protein) based on a broken-line analysis of the relationships with WGR, SGR, FCR, PRR, and PER.

     

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