饲料n-3高不饱和脂肪酸水平对较大规格军曹鱼生长性能、血清生化指标以及肌肉和肝脏脂肪酸组成的影响

Effects of Dietary n-3 Highly Unsaturated Fatty Acids Level on Growth Performance,Serum Biochemical Indices and Fatty Acid Composition in Muscle and Liver of Larger Cobia(Rachycentron canadum)

本试验旨在考察饲料n-3高不饱和脂肪酸(HUFA)水平对较大规格军曹鱼生长性能、血清生化指标及肌肉和肝脏脂肪酸组成的影响,以确定较大规格军曹鱼饲料中n-3HUFA的适宜水平。以白鱼粉、酪蛋白和去皮豆粕为主要蛋白质源,调节饲料中鱼油和玉米油的添加量,制成n-3HUFA水平分别为0.49%、0.73%、0.98%、1.41%、1.51%、2.06%及2.83%的7种等氮等能的试验饲料,投喂初重为70 g的军曹鱼8周。每种饲料投喂3个网箱(重复),每个网箱放养30尾鱼。结果显示:1)增重率(WGR)和特定生长率(SGR)随饲料n-3HUFA水平的升高呈先升高后降低趋势,0.73%～1.51%组的WGR和SGR显著高于0.49%和2.83%组(P<0.05)。2.83%组的成活率(SR)显著低于其他各组(P<0.05)。鱼体粗脂肪含量随饲料n-3HUFA水平的升高呈先上升后下降的趋势,0.98%和1.41%组鱼体粗脂肪含量显著高于2.06%和2.83%组(P<0.05)。2) 0.49%组血清谷丙转氨酶(ALT)活性显著高于2. 06%组(P <0. 05); 0. 49%组血清甘油三酯(TG)显著高于其他各组(P<0.05);血清总胆固醇(CHOL)含量随饲料n-3HUFA水平的升高呈先升高后下降趋势,以0.73%组最高,显著高于0.49%、2.06%和2.83%组(P<0.05); 0.98%组血清高密度脂蛋白(HDL)含量显著高于其他各组(P<0.05); 0.98%～2.83%组血清低密度脂蛋白(LDL)含量显著高于0.49%和0.73%组(P<0.05)。3)肌肉和肝脏C14∶0和C21∶0含量均以2.83%组最高,各组肌肉和肝脏C16∶0含量和饱和脂肪酸总量(∑SFA)无显著差异(P> 0.05)。肌肉和肝脏C18∶1n-9、单不饱和脂肪酸总量(∑MUFA)及C18∶2n-6含量均随饲料n-3HUFA水平的升高而下降。随饲料n-3HUFA水平的升高,肌肉和肝脏n-6多不饱和脂肪酸总量(∑n-6PUFA)呈先上升后稳定趋势,C20∶5n-3(EPA)、C22∶5n-3、C22∶6n-3(DHA)含量及n-3多不饱和脂肪酸总量(∑n-3PUFA)和n-3HUFA总量(∑n-3HUFA)均呈逐渐升高趋势。综上,饲料中添加n-3HUFA有助于提高较大规格军曹鱼的生长性能,降低体脂沉积,促进脂肪代谢,并可影响肌肉和肝脏脂肪酸组成。以SGR为评价指标,由折线模型得出较大规格军曹鱼饲料中n-3HUFA的适宜水平为0.95%。

This experiment was carried out to determine the effects of dietary n-3 highly unsaturated fatty acids（n-3 HUFA） level on growth performance,serum biochemical indices and fatty acid composition in muscle and liver of larger cobia（Rachycentron canadum）,in order to determine the suitable dietary n-3 HUFA level of larger cobia.Seven isonitrogenous and isoenergetic experimental diets were formulated with fish meal,casein and peeled soybean meal as main protein sources and different proportions of fish oil and corn oil as lipid sources,and cobias with the initial body weight of 70 g were fed 7 isonitrogenous and isoenergetic diets containing grade levels of n-3 HUFA（0.49%,0.73%,0.98%,1.41%,1.51%,2.06% and 2.83%） for 8 weeks.Fish in 3 cages（replicates） fed one kind of diet,and each cage cultured 30 fish.The results showed as follow s：1） the weight gain rate（WGR） and specific grow th rate（SGR） were increased firstly and then decreased with the dietary n-3 HUFA level increasing,and those in 0.73% to 1.51% groups were significantly higher than those in0.49% and 2.83% groups（P〈0.05）.The survival rate（SR） in 2.83% group was significantly lower than that in other groups（P〈0.05）.The body crude lipid content was increased firstly and then decreased with the dietary n-3 HUFA level increasing,and that in 0.98% and 1.41% groups was significantly higher than that in2.06% and 2.83% groups（P〈0.05）.2） Serum alanine transaminase（ALT） activity in 0.49% group was significantly higher than that in 2.06% group（P〈0.05）.Serum triglyceride（TG） content in 0.49% group was significantly higher than that in other groups（P〈0.05）.Serum total cholesterol（CHOL） content was increased firstly and then decreased with the dietary n-3 HUFA level increasing,and the highest value was found in 0.73% group,which significantly higher than 0.49%,2.06% and 2.83% groups（P〈0.05）.Serum highdensity lipoprotein（HDL） content in 0.98% group was significantly higher than that in other groups（P〈0.05）.Serum low-density lipoprotein（LDL） content in 0.98% to 2.83% groups was significantly higher than that in 0.49% and 0.73% groups（P〈0.05）.3） The highest C14 ∶ 0 and C21 ∶ 0 contents in muscle and liver were found in 2.83% group,and C16∶ 0 content and the total amount of saturated fatty acids（∑SFA） were not significantly influenced by dietary n-3 HUFA level（P〉0.05）.C18∶ 1 n-9,C18∶ 2 n-6 contents and the total amount of monounsaturated fatty acids（∑ M UFA） all showed a decreased trend with the dietary n-3 HUFA level increasing.With the dietary n-3 HUFA level increasing,the total amount of n-6 polyunsaturated fatty acids（∑n-6 PUFA） increased firstly and then kept stable,and the contents of C20∶5 n-3（eicosapentaenoic acid）,C22∶ 5 n-3,C22∶6 n-3（docosahexaenoic acid）,the total amount of n-3 polyunsaturated fatty acids（∑ n-3 PUFA） and the total amount of n-3 HUFA（∑n-3 HUFA） all showed a gradually rising tendency（P〈0.05）.In conclusion,dietary n-3 HUFA positively improves grow th performance of lager cobia and decreases the body lipid deposition,enhances lipid metabolization,and affects the fatty acid composition in body and liver.With the SGR as evaluation index,the suitable dietary n-3 HUFA level of larger cobia is 0.95% by broken-line model.