饲料脂肪含量对两种规格的军曹鱼生长、体组成和血清生化指标的影响

实验旨在确定2种规格军曹鱼的脂肪需求, 同时探索不同含量的脂肪对2种规格军曹鱼体组成及血清生化指标的影响。以鱼粉、酪蛋白和豆粕为蛋白源, 鱼油为脂肪源, 通过添加不同配比的鱼油配制6种脂肪水平5.27%、8.22%、10.81%、14.26%、17.32%和20.94% (占干重)]的等氮实验饲料。挑选(38.24±0.30) g (25尾/箱, 40 g规格)和(529.17±5.67) g (10尾/箱, 500 g规格)2种规格的军曹鱼, 置于浮式网箱(1.3 m×1.3 m×2.5 m)中每日饱食投喂2次, 分别进行10周和8周的摄食生长实验。结果表明:随着饲料脂肪含量的增加, 2种规格军曹鱼特定生长率(SGR)和饲料效率(FER)均先上升再下降, 而脏体比(VSI)与肥满度(CF)均显著升高(P<0.05)。另外, 随着饲料脂肪水平的增加, 40 g规格的军曹鱼肝体比(HSI)、鱼体、肝脏和肌肉脂肪含量均显著升高, 鱼体水分和蛋白含量显著下降(P<0.05), 而500 g规格的军曹鱼各处理之间未发现显著差异(P>0.05)。随着饲料脂肪水平的增加, 40 g规格的军曹鱼, 血清总甘油三酯(TG)、血清总胆固醇(TC)、高密度脂蛋白-胆固醇(HDL-C)、低密度脂蛋白-胆固醇(LDL-C)及血糖(Glu)含量显著增加(P<0.05), 而500 g规格的军曹鱼, 除血清TG在各处理之间呈现出显著差异外(P<0.05), 其余指标在各处理之间均未发现显著差异(P>0.05)。综上所述, 以SGR和FER为评价指标, 40 g左右规格的军曹鱼脂肪需求量为13.97%—14.16%, 500 g左右规格的军曹鱼脂肪需求量为13.18%—13.47%。

THE EFFECT OF DIFFERENT LIPID LEVELS ON THE GROWTH PERFORMANCE,BODY COMPOSITION AND PLASMA BIOCHEMICAL INDICES IN COBIA (RACHYCENTRON CANADUM L.) AT TWO DIFFERENT SIZES

The purpose of this study was to investigate dietary lipid requirement and the effect of different lipid levels on the body composition and plasma biochemical indices in cobia (Rachycentron canadum L.) at two different body sizes (initial weight: 40 g vs. 500 g). Six isonitrogenous diets were formulated using fish meal, soybean meal and wheat meal as the protein source and fish oil as lipid source, with six different lipid contents of 5.27%, 8.22%, 10.81%, 14.26%, 17.32% and 20.94% (at a dry matter basis), respectively. Fish at two different growth stages were randomly distributed to seawater floating net cages (1.5 m×1.5 m×2.5 m) at a density of 25 and 10 fish per net cage, respectively. Each diet was fed to triplicate groups of fish twice daily to satiation for 10 weeks (40 g) and 8 weeks (500 g), respectively. Specific growth rate (SGR) and feed efficiency ratio (FER) significantly increased and then decreased with increasing dietary lipid levels at both developmental stages. The Viscerosomatic index (VSI) and Condition factor (CF) increased significantly with the increase of dietary lipid levels. Significantly higher Hepatosomatic index (HSI), whole-body, liver and muscle lipid contents and lower moisture and protein contents were observed in fish feed the diets containing higher lipid among small fish groups, but no significant difference was detected among large body size groups among above parameters. In addition, the contents of TC, TG, HDL-C, LDL-C and Glu increased significantly with the increasing lipid levels among small fish groups, there was no significant effect among large fish groups in these indices except TG. The overall results showed that based on SGR and FER, the diet containing 13.97%—14.16% and 13.18%—13.47% lipid was most suitable for the cobia culture at the body size of 40 g and 500 g, respectively.