饲料LNA/LA比对鲤幼鱼生长性能,肝脏脂肪酸组成及Δ6 fad,elovl5 mRNA表达的影响

Effects of dietary LNA/LA ratio on growth,hepatic fatty acid profiles and△6 fad,elovl5 mRNA expression in common carp(Cyprinus carpio)

为了探讨饲料LNA/LA比对鲤幼鱼生长性能和LC-PUFA合成代谢的影响,本研究以鱼油和混合植物油(花生油和紫苏籽油)为脂肪源配制5组等氮等脂饲料。对照组(D1)以鱼油为唯一脂肪源,其他5组实验饲料以花生油和紫苏籽油为脂肪源,且LNA/LA比分别为0.02(D2)、0.46(D3)、1.09(D4)和1.53(D5)。8周养殖实验后,分析各处理组鱼体的生长性能指标、肝脏脂肪酸组成,肝脏Δ6 fad-a/b和elovl5-a/b基因表达水平。结果显示,与对照组相比,植物油饲料对鱼体增重率(WGR)、特定生长率(SGR)和饲料系数(FCR)无显著影响,但显著影响了鱼体肝脏LC-PUFA水平,提高了肝脏Δ6 fad-a和elovl5-a mRNA表达水平。在各植物油组之间,饲料LNA/LA比显著影响了鱼体WGR和SGR指标,其中D2和D4组鱼体生长表现较好;随着饲料中LNA/LA比的升高,鱼体肝脏LC-PUFA水平,以及Δ6 fad-a和elovl5-a mRNA表达水平也随之增加,其中D4组鱼体肝脏Δ6 fad-a和elovl5-a mRNA表达量最高,且其LC-PUFA含量显著高于D2和D3组。由此可见,植物油饲料尽管不影响鲤正常生长,但影响了鱼体肝组织LC-PUFA含量。然而,饲料中添加适宜的LNA/LA比(1.09∶1)可促进鲤肝脏Δ6 fad-a和elovl5-a mRNA的表达,最大限度地提高鱼体内源LC-PUFA合成量,从而有效地降低植物油饲料对鱼体组织LC-PUFA含量的负面影响。

To evaluate the effects of dietary α-linolenic acid （LNA, 18：3n-3）/linoleic acid （LA, 18：2n-6） ratios on growth performance and LC-PUFA biosynthesis in common carp, we designed five iso-nitrogenous and iso- energetic diets for eight weeks of feeding trial. The control diet （D1） was only supplemented with fish oil as lipid source, while the mix of peanut oil and perilla oil with varying LNA/LA ratios of 0.02, 0.46, 1.09 and 1.53 was used as lipid source for the experimental groups [D2, D3, D4 and D5, VO （vegetable oil） diets], respectively. The results showed that, there were no differences among control group and VO groups in WGR, SGR and FCR. Compared with the control group, the hepatic LC-PUFA levels were significantly low in VO groups, whereas, the hepatic △6fad-a and elovl5-a mRNA expression levels were significantly improved by VO diets. Among the four VO groups, the WGR and SGR were significantly affected by dietary LNA/LA ratios, with higher growth in D4 and D2 groups. Additionally, the hepatic LC-PUFA levels, △6fad-a and elovl5-a mRNA expression levels were higher in the fish fed higher ALA/LA ratios diets. In particular, the highest hepatic LC-PUFA levels were observed in D4 groups, and consistent with this, hepatic △6fad-a and elovl5-a mRNA with the highest level were also showed in D4 groups. The results indicate that VO diets have a negative effect on the hepatic LC-PUFA levels in common carp. However, the optimal balance LNA/LA supplement （1.09 ： 1） have been successful in raising the efficiency of LC-PUFA production by improving the hepatic △6 fad-a and elovl5-a mRNA expression, and decreasing the negative impact of VO diets on tissue LC-PUFA concentration in this fish species.