饲料不同脂肪和脂肪酶水平对细鳞鲑生长性能、血清生化指标和肝脏抗氧化性能的影响

Effects of dietary lipid and lipase levels on growth performance, serum biochemical indices, and liver antioxidant activity of Brachymystax lenok

中文关键词: 细鳞鲑  外源脂肪酶  生长性能  血清生化指标  肝脏抗氧化性能

英文关键词: Brachymystax lenok  Exogenous lipase  Growth performance  Serum biochemical indices  Liver antioxidant activity

中文摘要:

      本实验旨在研究饲料不同脂肪和脂肪酶水平对细鳞鲑(Brachymystax lenok)生长性能、血清生化指标和肝脏抗氧化性的影响。采用2×3双因素实验设计，配制2个脂肪水平(180和220 g/kg)和3个脂肪酶水平(0、2500和5000 U/kg)的6种实验饲料，即C-0、C-2500、C-5000和H-0、H-2500、H-5000。挑选270尾初始体重为(7.34±0.16) g的细鳞鲑，随机分为6个组，每组3个重复，每个重复15尾鱼。各组实验鱼分别投喂6种不同的实验饲料，养殖63 d。结果显示，不同脂肪含量和脂肪酶水平对终末平均体重存在极显著交互作用(P<0.01)，对增重率(WGR)和特定生长率(SGR)存在显著的交互作用(P<0.05)，脂肪与脂肪酶二者均对机体的生长性能产生影响，其中，同一脂肪水平，鱼体重、WGR和SGR均以C-5000组最高。H-0、H-2500、H-5000组血液中的谷丙转氨酶(ALT)分别低于C-0、C-2500、C-5000组，其中，H-0、H-5000与C-0、C-5000组存在显著差异(P<0.05)；H-0、H-2500、H-5000组的低密度脂蛋白胆固醇(LDL-C)分别高于C-0、C-2500、C-5000组，其中，H-0、H-2500与C-0、C-2500组存在显著差异(P<0.05)。随着脂肪酶水平升高，肝脏中谷胱甘肽过氧化物酶(GPX)水平提高，且相同脂肪酶水平的220 g/kg组GPX高于180 g/kg组。综上所述，在脂肪水平为183.7 g/kg、脂肪酶添加量为5000 U/kg时，可以明显改善细鳞鲑幼鱼的生长和抗氧化性能。

英文摘要:

      With the increasing demand for marine fish and cold-water predatory fish, to ensure its scale and industrialization in the process of breeding and to provide safe, high-quality, and healthy aquatic animal food for the society, the quality requirements of aquatic compound feed in the industry are increasing. Among the three nutrients, predatory fish have a poor ability to use sugar. Protein is the most expensive raw material, and the final product of its metabolism is ammonia, which can lead to the deterioration of water quality. Fat provides energy for fish growth, and essential fatty acids promotes the absorption of fat-soluble vitamins, and promotes protein deposition and utilization as a non-protein energy substance. Therefore, increasing the oil content in predatory fish feed and reducing the use of protein as energy can save feed protein and increase economic benefit. Different fish have different responses to nutrients and energy in feed. The fat metabolism of cultured fish has a certain species-specificity. It is generally believed that cold-water fish have a higher dietary fat requirement. The fat requirement of juvenile salmonids is 20%~30%, much higher than that of warm water fish. As a cold-water fish, Brachymystax lenok has successfully evolved key genotypic or phenotypic traits to adapt to growing at low temperatures, with fat requirements in the range of 17%~19%, slightly below the recommended fat requirements for regular Salmonidae fish. The high-fat feed has been widely used in carnivorous cold-water fish. As physiological conditions limit the demand and utilization capacity of fat, long-term intake of high-fat feed will easily cause fat metabolism disorder and meat quality decline during the breeding period, which seriously affects the health and quality of fish. Nutritional regulation of fat metabolism has become feasible means to reduce body fat deposition and improve meat quality. Therefore, it is particularly urgent to elucidate the fat metabolism mechanism and nutrition regulation of predatory fish. Lipase plays an essential role in lipid metabolism. As an enzyme with affinity at the oil-water interface, glycerol and fatty acids obtained after lipid hydrolysis can provide energy for the animal body and be utilized for its growth. Therefore, adding lipase in feed to regulate body fat nutrition has garnered considerable attention. Exogenous lipase has been well used in broilers and pigs to improve growth performance and physiological metabolism. It is also widely used in fish. However, it is rarely reported in the studies on cold water and freshwater fish nutrition. B. lenok is a rare and cold-water fish found in clear rivers and streams in China. The optimum temperature range for its growth is 18~20℃, and it has very high economic, edible, and research value. This study aims to, through adding different levels of lipase in different fat feed, use lipase in fat metabolism under the effect of high-fat feedstuff stress B. lenok to fat metabolism regulation, nutrition research on B. lenok growth performance, serum biochemical indices, and liver antioxidant effect, for lipase in B. lenok feeds for young fish provide a reference for the application. In this experiment, a 2×3 two-factor experimental design was used to prepare six experimental diets with two lipid levels (180 and 220 g/kg) and three lipase levels (0, 2500, and 5000 U/kg): C-0, C-2500, C-5000 and H-0, H-2500, H-5000. A total of 270 B. lenok with an initial body weight of (7.34±0.16) g were randomly divided into six groups with three replicates and 15 fish per replicate. Fish in each group were fed six different experimental diets for 63 days. The results show that different fat content and lipase level had extremely significant interaction on average body weight (P<0.01) and significant interaction on weight gain rate and specific growth rate (P<0.05). Both fat and lipase had an impact on the growth performance of the body. The body weight, weight gain rate, and specific growth rate of fish in the C-5000 group were the highest. Serum alanine aminotransferase (ALT) levels in H-0, H-2500, and H-5000 groups were lower than those in C-0, C-2500, and C-5000 groups, respectively. There were significant differences between H-0 and H-5000 groups and those in C-0 and C-5000 groups (P<0.05). The low-density lipoprotein cholesterol (LDL-C) in H-0, H-2500, and H-5000 groups was higher than in C-0, C-2500, and C-5000 groups, respectively. There was a significant difference between H-0 and H-2500 groups, and the C-0 and C-2500 groups (P<0.05). With the increase of lipase level, liver glutathione peroxidase (GPX) level increased. The GPX of the 220 g/kg group with the same lipase level was higher than that of the 180 g/kg group. In conclusion, the growth and antioxidant performance of juvenile B. lenok can be significantly improved at a lipid level of 183.7 g/kg, and the lipase level of 5000 U/kg.