饲料中n-3/n-6多不饱和脂肪酸水平对黄河鲤幼鱼生长性能及生长相关基因mRNA表达的影响

Effects of dietary n-3/n-6 polyunsaturated fatty acids ratio on growth performance and growth-related genes mRNA expression in common carp(Cyprinus carpio haematopterus)

为了分析饲料n-3/n-6多不饱和脂肪酸(PUFAs)水平对黄河鲤幼鱼生长性能和生长相关基因的影响,实验以鱼油和混合植物油(花生油和紫苏籽油)为脂肪源配制5组等氮等能饲料。对照组(T1)以鱼油为唯一脂肪源,18:3 n-3/18:2 n-6为0.97,第二组(T2)以花生油为唯一脂肪源,18:3 n-3/18:2 n-6为0.02,其他3组实验饲料以花生油和紫苏籽油为脂肪源,且n-3/n-6比值分别为0.46(T3)、1.09(T4)和1.53(T5)。10周养殖实验结束后,分析各组鱼体的生长性能、血清中生长激素(GH)含量及不同部位肌肉中生长相关基因的表达水平。结果显示,与对照组相比,n-3/n-6对鱼体的脏体比(VSI)、饲料系数(FCR)、摄食率(FI)无显著影响,增重率(WGR)随n-3/n-6比值的增加先升后降,n-3/n-6比值等于1.09时,WGR达到峰值,为218.53%±24.32%。T2组血清GH含量显著高于其他处理组,随着n-3/n-6比值增大GH含量逐渐降低。背部肌肉中生长相关基因gh、ghr、igf-1和myod均表现为先升后降的趋势,igf-1r为先降后升,mstn无显著差异。红肌中gh、myod含量逐渐降低,ghr、mstn不存在显著差异,igf-1与背部肌肉相似,先升后降,igf-1r先降后升。腹部肌肉中gh、ghr和igf-1表达情况与背部肌肉一致,igf-1r和myod的表达不存在显著差异。T2组和T4组背部肌肉肌纤维数目存在显著差异,且T4组肌纤维较T2组粗。研究表明,n-3/n-6不仅在一定程度上提高鱼体的WGR,且不同比例的n-3/n-6水平会影响血清GH的含量,不同部位肌肉组织中GH/IGF轴生长相关基因的水平也受饲料中n-3/n-6比例的影响。

To analyze the influence of n-3/n-6 PUFAs levels on the growth performance and growth- related genes mRNA expression in common carp, five isonitrogenous and isoenergetic experimental diets based on fish oil and mixed vegetable oil were fed to the Cyprinus carpio haematopterus for 10 weeks. The control diet (T1) was only supplemented with fish oil as lipid source, n-3/n-6 ratio was 0.97. the second group (T2) was only supplemented with peanut oil, n-3/n-6 ratio was 0.02. n-3/n-6 ratio of the other three experiments groups were 0.46(T3), 1.09 (T4) and 1.53 (T5) with peanut oil and perilla seed oil as feed source. After 10 weeks cultivation experiments, we checked each group for fish growth performance, serum growth hormone and growth-related gene expression level in different parts of muscle tissue. The results indicated that there were no significant differences in the viscerosomatic index (VSI), feed coefficient (FCR), feed intake(FI)among the five tested groups. Weight gain rate of the fish (WGR) was raised first and subsequently declined with the increase of the n-3/n-6 ratio. WGR climbed the peak at T4 group. The serum GH levels of T2 group were significantly higher than those of others, and the level of GH in serum gradually reduced with the increase of of n-3/n-6 ratio. The expression levels of growthrelated genes in the dorsal muscles showed that gh, ghr, igf-1 and myod were enhanced first and subsequently declined. However, igf-1r displayed the opposite expressive trend, while there were no significant differences in mstn level among the five treated groups. In red muscle, the expression levels of gh and myod were gradually decreased with the increase of n-3/n-6 ratio, and the expressions of ghr and mstn exhibited no significant differences in five groups. Besides, the expressive trends of igf-1 and igf-1r were similar to that of dorsal muscles. Interestingly, the expressions of gh, ghr and igf-1 in the abdominal muscles were consistent with the dorsal muscles. But, the levels of igf-1r and myod manifested no significant difference in five tested groups. There were significant differences in the number of muscle fibers in the T2 group and T4 group, and the muscle fibers in T4 group were thicker than those of T2. This study showed that vegetable oil contributed to improve the WGR of the fish and the n-3/n-6 ratio of the diets not only affected the serum GH level, but also influenced the growth related genes of GH/IGF axis in different parts of the muscle tissues.