低鱼粉饲料添加赖氨酸对异育银鲫“中科5号”幼鱼生长性能及代谢的影响

DIETARY LYSINE SUPPLEMENTATION ON GROWTH PERFORMANCES AND METABOLISM IN JUVENILE GIBEL CARP (CARASSIUS GIBELIO VAR. CAS V) FED LOW FISH MEAL DIETS

  • 摘要: 实验以初重(8.70±0.03) g的异育银鲫“中科5号”(Carassius gibelio var. CAS Ⅴ)幼鱼为研究对象, 分别投喂低鱼粉饲料中添加0、2%、4%赖氨酸的饲料49d, 以探究低鱼粉饲料中添加不同水平赖氨酸对异育银鲫“中科5号”生长性能、鱼体生化组成、营养沉积、血浆代谢物及肌肉中赖氨酸感知和应答、肌肉生长相关基因表达的影响。实验结果显示, 饲料中添加不同水平的赖氨酸对异育银鲫“中科5号”的摄食率、特定生长率、饲料效率、蛋白沉积率、脂肪沉积率没有显著性影响(P>0.05)。饲料中添加2%赖氨酸组, 全鱼蛋白质含量显著高于其他组(P<0.05), 全鱼总氨基酸含量、总必需氨基酸含量显著高于其他两个处理组(P<0.05), 其中赖氨酸、精氨酸、异亮氨酸、亮氨酸、苯丙氨酸、苏氨酸和缬氨酸等7种必需氨基酸含量显著高于其他各组(P<0.05)。肌肉的氨基酸组成在各组间无显著性差异(P>0.05)。血浆葡萄糖、甘油三酯和总胆固醇含量在各组间无显著性差异(P>0.05)。血浆游离氨基酸组成没有受到饲料赖氨酸水平的显著影响(P>0.05)。饲料中添加赖氨酸对肌肉中赖氨酸感知和应答相关关键基因表达无显著性影响(P>0.05), 4%赖氨酸组肌肉myog的基因表达量高于2%赖氨酸组(P<0.05)。结果表明, 低鱼粉饲料中添加2%赖氨酸可以在一定程度上提高异育银鲫“中科5号”全鱼必需氨基酸和蛋白质含量, 可为异育银鲫“中科5号”的配方设计提供支撑。

     

    Abstract: How to improve utilization of protein especially non-fishmeal protein in fish is a problem demanding prompt solution in aquatic nutrition. Studies in mammal showed that G protein coupled receptor family C, group 6, subtype A (GPRC6A) could sense the amino acids, and then regulate the muscle growth via ERK-mTOR signal pathway. But mechanisms of sensing and responding to lysine in fish are still unclear. A 7-week feeding experiment was conducted to investigate the effects of dietary lysine supplementation in low fish meal diets on the growth performances, biochemical composition, nutrient deposition, plasma biochemical indices and metabolism related gene expression in the muscle of gibel carp (Carassius gibelio var. CAS Ⅴ) (initial mean body weight: 8.70±0.03 g). The diet containing 5% fish meal was set as the control group (LL), the other groups were supplemented with 2% (ML) and 4% (HL) lysine, respectively. The results showed that lysine supplementation in low fishmeal diet had no significant effect on the feeding rate (FR), specific growth rate (SGR), feed efficiency (FE), protein retention efficiency (PRE), lipid retention efficiency (LRE) in the gibel carp (P>0.05). Dietary supplement with 2% lysine did not affect the condition factor (CF), hepatosomatic index (HSI) and viscerosomatic index (VSI) in the gibel carp (P>0.05). The 4% lysine group had no effect on the CF and VSI, but significantly decreased the HSI (P<0.05). The protein content of whole body in ML group was higher than that in other two groups (P<0.05), and the total amino acid level and the total essential amino acid level was also higher than LL group and HL group (P<0.05). The levels of seven essential amino acids including lysine, arginine, isoleucine, leucine, phenylalanine, threonine and valine in the whole body was highest in the fish fed diet supplemented with 2% lysine (P<0.05). The lysine supplementation in low fishmeal diet had no significant effect on the levels of protein and moisture in the muscle of gibel carp (P>0.05), but the HL diet decrease the lipid contents in the muscle (P<0.05). Plasma glucose, triglyceride and cholesterol levels showed no significant difference in the three groups (P>0.05). The diets supplemented with lysine did not affect the plasma amino acid profile in gibel carp (P>0.05). The mRNA levels of genes involved in sensing and responding to lysine including gprc6a, β-arrestins, erk, rheb, tsc2, tor, s6k1, 4ebp2 and eif4e in the muscle of gibel carp were not affected by the diets (P>0.05). The lysine supplementation in low fishmeal diet had no significant effect on relative expression of genes involved in regulating myofiber growth and development including myod, myf5, mstn, mylc and pax7α in the muscle of gibel carp (P>0.05), but the mRNA levels of myog in the HL group was higher than that in the ML group (P<0.05). These results suggested that low fish meal diet supplemented with 2% lysine could increase the total essential amino acid level and protein level in the whole body of gibel carp “CAS Ⅴ”, but the mechanism remains to be fully elucidated, which might offer new insights into improving the feed formula of gibel carp “CAS Ⅴ”.

     

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