养殖密度对厚颌鲂幼鱼生长、饲料利用及肠道抗氧化应激性能的影响

Effects of Stocking Density on Growth, Feed Utilization and Intestinal Oxidative Stress Resistance in Juvenile Megalobrama pellegrini (Tchang, 1930)

中文关键词: 厚颌鲂  养殖密度  生长  饲料利用  肠道氧化应激

英文关键词: Megalobrama pellegrini  Stocking density  Growth  Feed utilization  Intestinal oxidative stress

中文摘要:

      本研究拟通过养殖实验确定厚颌鲂(Megalobrama pellegrini)幼鱼最适养殖密度；同时，利用酶学和分子生物学手段分析养殖密度对厚颌鲂幼鱼肠道抗氧化酶活性及氧化应激相关基因表达的影响。实验设计5个密度处理组，分别为0.15 kg/m3(50尾/桶)、0.24 kg/m3(80尾/桶)、0.34 kg/m3 (110尾/桶)、0.42 kg/m3(140尾/桶)和0.50 kg/m3(170尾/桶)，每组设置3个平行，实验周期为42 d。结果显示，当养殖密度从0.15 kg/m3逐渐升高到0.50 kg/m3时，厚颌鲂幼鱼生长(增重率和特定生长率)呈先上升后下降的趋势，且在最大密度时(0.50 kg/m3)增重率和特定生长率显著低于0.34 kg/m3密度实验组(P<0.05)。同时，最高养殖密度处理组(0.50 kg/m3)饲料系数显著高于中低密度实验组(0.15、0.24和0.34 kg/m3) (P<0.05)，说明过高养殖密度不利于厚颌鲂幼鱼的生长和饲料利用。实验表明，提高养殖密度并未影响厚颌鲂幼鱼成活率(P>0.05)，各组存活率均较高(>97%)。当养殖密度为0.34 kg/m3时，厚颌鲂幼鱼全鱼粗蛋白和粗脂肪含量显著高于其他各密度实验组(P<0.05)。厚颌鲂幼鱼肠道抗氧化应激相关指标受到养殖密度的显著影响，其中，0.24和0.34 kg/m3密度处理组鱼体肠道总抗氧化能力显著高于最低密度组(0.15 kg/m3)和高密度组(0.42、0.50 kg/m3)(P<0.05)；最高密度实验组(0.50 kg/m3)肠道超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性最低，而丙二醛(MDA)含量最高(P<0.05)；谷胱甘肽(GSH)含量最高值出现在0.34 kg/m3处理组，显著高于其他各实验组(P<0.05)。最低密度实验组(0.15 kg/m3)厚颌鲂幼鱼肠道细胞色素P450 (CYP1 A)基因相对表达量显著低于较高密度实验组(0.42 kg/m3)(P<0.05)；最高养殖密度组(0.50 kg/m3)鱼体肠道转录因子NF-E2相关因子2 (Nrf2)基因相对表达量最高，而锰超氧化物歧化酶基因(MnSOD)相对表达量最低，与0.34 kg/m3密度处理组间有显著性差异(P<0.05)，说明养殖密度过高时能引起鱼体的氧化应激反应。研究表明，体重为0.45~1.36 g的厚颌鲂幼鱼最适养殖密度为0.34 kg/m3，该结果可为提高厚颌鲂苗种培育效率，促进其种质资源恢复提供理论基础。

英文摘要:

      This study aimed to determine the optimal stocking density for juvenile Megalobrama pellegrini. Meanwhile, enzymology and molecular biology analyses were performed to analyze the effects of stocking density on the intestinal antioxidant enzyme activities and the expression of stress-related genes in this fish species. 5 density treatments groups, including 0.15 kg/m3 (50 tails/barrel), 0.24 kg/m3 (80 tails/barrel), 0.34 kg/m3 (110 tails/barrel), 0.42 kg/m3 (140 tails) /Barrel), 0.50 kg/m3 (170 tails/barrel) were set up in triplicate. The experimental period was 42 days. The results showed that fish growth performance (weight gain rate and specific growth rate) increased as the stocking density increased from 0.15 kg/m3 to 0.34 kg/m3, but no significant differences were found among the groups (P>0.05). When stocking density continued to increase, fish growth performance decreased, and significantly lower growth was found in fish reared at a stocking density of 0.50 kg/m3 compared with the 0.34 kg/m3 group (P<0.05). Meanwhile, the highest density group (0.50 kg/m3) had a significantly higher feed conversion ratio compared with the low and medium stocking density groups (0.15 kg/m3, 0.24 kg/m3, 0.34 kg/m3) (P<0.05), which indicated that the higher stocking density had side effects on fish growth and feed utilization. The results also showed that increasing the stocking density did not significantly affect the survival rate of M. Pellegrini (P>0.05), and the survival rate of each group was very high (>97%). The crude protein and crude fat content of the whole-body in the fish of the 0.34 kg/m3 group were significantly higher than those in other experimental groups (P<0.05). The intestinal antioxidant enzymes and other related indexes of fish were significantly affected by stocking density. Specifically, the 0.24 kg/m3 and 0.34 kg/m3 groups had significantly higher total antioxidant capacity than the lowest-density group (0.15 kg/m3) and the higher-density groups (0.42 kg/m3, 0.50 kg/m3) (P<0.05); the activities of intestinal superoxide dismutase and catalase were lowest at 0.50 kg/m3, while content of malondialdehyde was the highest (P<0.05); the highest value of glutathione content appeared in the 0.34 kg/m3 group and was significantly higher than that of other experimental groups (P<0.05). The lowest density experimental group, 0.15 kg/m3, had the lowest intestinal CYP1 A gene expression, but a significant difference was only found between the 0.42 kg/m3 experimental group (P<0.05). Fish in the 0.50 kg/m3 group had significantly higher relative expression levels of the Nrf2 gene and significantly lower relative expression levels of MnSOD compared with the 0.34 kg/m3 density treatment group (P<0.05), which indicated that the intestinal oxidative stress response was induced when the stocking density was too high. The results of this study indicated that M. Pellegrini at the weight of 0.45~1.36 g could be cultured at a density of 0.34 kg/m3, which will provide a theoretical basis for improving breeding efficiency and promoting the restoration of the resources of M. Pellegrini.