饲料脂肪水平对吉富罗非鱼生长性能及其在低温应激下血清生化指标和肝脏脂肪酸组成的影响

Effects of Dietary Lipid Level on Growth Performance of Genetic Improvement of Farmed Tilapia(GIFT,Oreochromis niloticus) and Its Serum Biochemical Indices and Fatty Acid Composition under Cold Stress

本试验旨在研究饲料脂肪水平对吉富罗非鱼(GIFT,Oreochromis niloticus)生长性能及其在低温应激下血清生化指标和肝脏脂肪酸组成的影响。在基础饲料(含1.95%脂肪)中添加0、4%、6%、8%豆油,制成4种不同脂肪水平(分别为1.95%、6.19%、8.03%和9.95%)的试验饲料,投喂平均体重为(37.0±1.0)g的吉富罗非鱼8周。每个处理设3个重复,每个重复25尾鱼。饲养试验结束后,以28℃为对照,水温按1℃/h的速率降至15℃进行低温应激试验。结果表明:1)各组间成活率(SR)、饲料系数(FCR)无显著差异(P>0.05),增重率(WGR)及特定生长率(SGR)随饲料脂肪水平的升高而显著增加(P<0.05),饲料脂肪水平达6.19%后增加不显著(P>0.05)。2)低温应激下,饲料脂肪水平对除葡萄糖(GLU)、甘油三酯(TG)外的其他血清生化指标有显著影响(P<0.05)。随饲料脂肪水平的升高,血清中GLU、总蛋白(TP)、胆固醇(CHOL)、TG、低密度脂蛋白胆固醇(LDL-C)水平逐渐升高,高密度脂蛋白胆固醇(HDL-C)水平先升高后降低,血清谷草转氨酶(AST)、谷丙转氨酶(ALT)活性略微下降后再升高。3)低温应激下,随饲料脂肪水平的升高,肝脏中饱和脂肪酸(SFA)比例下降,不饱和脂肪酸(UFA)比例上升。饲料脂肪水平对n-3多不饱和脂肪酸(n-3 PUFA)、n-6多不饱和脂肪酸(n-6 PUFA)比例及n-3/n-6有显著影响(P<0.05)。由此得出,适当的饲料脂肪水平(6.19%)能够促进吉富罗非鱼的生长,提高其抗低温应激的能力;过高的饲料脂肪水平(8.03%及以上)可导致血液转氨酶活性升高,加重低温应激下鱼类代谢负担,不利于鱼体健康及生长。

The objective of this study was to evaluate the effects of dietary lipid level on growth performance of genetic improvement of farmed tilapia(GIFT,Oreochromis niloticus) and its serum biochemical indices and fatty acid composition under cold stress.Fish with an average body weight of(37.0±1.0) g were fed experimental diets containing 4 different levels(1.95%,6.19%,8.03% and 9.95%,respectively) of lipid which were supplemented with 0,4%,6% and 8% of soybean oil in basal diet(1.95% lipid) for 8 weeks.Each treatment contained 3 replicates and each replicate contained 25 fish.After feeding experiment,experimental fish were acclimated at 28 ℃ as control,the water temperature was reduced from 28 ℃ to 15 ℃ at a rate of 1 ℃/h to proceed cold stress experiment.The results showed as follows: 1) the survival rate(SR) and feed conservation rate(FCR) were not significantly influenced by dietary lipid level(P>0.05).The weigh gain rate(WGR) and specific growth rate(SGR) increased significantly(P<0.05) with dietary lipid level increasing until dietary lipid level arrived at 6.19%.2) Under the cold stress,dietary lipid level had significant influence on serum biochemical indices except glucose(GLU) and triglyceride(TG) levels(P<0.05).With dietary lipid level increasing,the levels of GLU,total protein(TP),TG,cholesterol(CHOL) and low density lipoprotein cholesterol(LDL-C) in serum gradually raised,and the serum high density lipoprotein cholesterol(HDL-C) level showed a rising trend and then gradually descended,while the activities of aspartate aminotransferase(AST) and alanine transarninase(ALT) in serum slightly decreased and then increased.3) Under the cold stress,the proportion of saturated fatty acid(SFA) in liver showed a descending trend and the proportion of unsaturated fatty acid(UFA) in liver showed a rising trend with dietary lipid level increasing.Dietary lipid level had significant influence on n-3 polyunsaturated fatty acid(PUFA) proportion,n-6 PUFA proportion and n-3/n-6(P<0.05).In conclusion,the optimal level of dietary lipid is 6.19%,which is beneficial to promote the growth of GIFT and its cold-resistance ability.When dietary lipid level reaches or exceeds 8.03%,the higher transaminase activity may burden the metabolism of liver,which is bad for health and growth of fish.