饲料中添加几丁聚糖对吉富罗非鱼幼鱼生长性能、免疫调控与抗海豚链球菌感染的影响

摘要

本试验旨在探讨饲料中添加几丁聚糖对吉富罗非鱼幼鱼生长性能、免疫调控与抗海豚链球菌感染的影响。选择健康、均重为(2.97±0.02) g的吉富罗非鱼375尾,随机分为5组,每组3个重复,每个重复25尾鱼。5组试验鱼分别饲喂在基础饲料中添加0(对照)、10、20、30和40 mL/kg几丁聚糖溶液(几丁聚糖的有效浓度为0.6%)的试验饲料。饲喂63 d后,测定各组试验鱼的生长性能指标、血常规指标、血清生化指标、头肾免疫相关基因的表达量以及海豚链球菌感染192 h后的累计死亡率。结果表明：与对照组相比,饲料中添加几丁聚糖对吉富罗非鱼幼鱼的特定生长率、存活率及血清总蛋白与甘油三酯含量无显著影响( P>0.05),但是添加量为10和20 mL/kg时可显著降低肝体比和血清皮质醇含量,提高血液红细胞数目、白细胞数目和血红蛋白浓度、红细胞压积以及血清溶菌酶和超氧化物歧化酶活力,促进头肾白细胞介素1β、肿瘤坏死因子α和干扰素基因的表达( P<0.05)；同时,添加量为20 mL/kg时还可显著增加饲料效率,降低血清葡萄糖、胆固醇与低密度脂蛋白胆固醇含量,提高高密度脂蛋白胆固醇含量( P<0.05)。海豚链球菌感染192 h后,10和20 mL/kg添加组的累计死亡率分别为30.06%和32.38%,显著低于对照组的51.19%与40 mL/kg添加组的77.55%( P<0.05)。由此得出,饲料中添加10和20 mL/kg几丁聚糖溶液有助于降低吉富罗非鱼幼鱼的肝体比与肝脏应激,提高非特异性免疫功能。同时,20 mL/kg添加量可以有效地促进饲料利用,降低血清脂肪沉积。在实际生产中,建议在吉富罗非鱼饲料中添加10~20 mL/kg的几丁聚糖溶液(几丁聚糖的有效浓度为0.6%),以促进吉富罗非鱼健康养殖。%The present study was performed to investigate the effects of chitosan supplementation on growth performance, immunomodulatory and against Streptococcus iniae infection of juvenile GIFT tilapia ( Oreochro-mis niloticus). A total of 375 health juvenile GIFT tilapia with an average body weight of (2.97±0.02) g were randomly divided into 5 groups with 3 replicates in each group and 25 fish in each replicate. Fish in those 5 groups were fed with a basal diet supplemented with 0 ( control) , 10, 20, 30 and 40 mL/kg chitosan solution (the effective concentration of chitosan was 0.6%). After 63-day feeding trial, the growth performance indi-ces, hematological parameters, serum biochemical parameters, the expression of immuno-related genes in head kidney and the cumulative mortality under Streptococcus iniae infection on 192 h were determined. The results showed as follows:compared with control group, chitosan supplementation had no significant effects on special growth rate ( SGR ) , survival ratio ( SR ) , serum total protein ( TP ) and triglyceride ( TC ) contents ( P>0.05) , but 10 and 20 mL/kg chitosan solution could reduce hepatosomatic index ( HIS) and serum cortisol ( COR) content, enhance blood white blood cell ( WBC) count, red blood cell ( RBC) count, haemoglobin ( Hb) concentration, haematocrit ( Hct) , serum lysozyme ( LZM) and superoxide dismutase ( SOD) activi-ties, and promote the expression of interleukin 1β( IL-1β) , tumor necrosis factorα( TNF-α) and interferonγ(IFN-γ) in head kidney (P<0.05). In addition, diet supplemented with 20 mL/kg chitosan solution could significantly increase feed efficiency ( FE) and serum high-density lipoprotein-cholesterol ( HDL-C) content, and reduce serum glucose ( GLU) , triglyceride ( TC) and low-density lipoprotein-cholesterol ( LDL-C) con-tents ( P<0.05) . Moreover, tilapia fed the diets supplemented with 10 and 20 mL/kg chitosan solution had 30.06% and 32.38% cumulative mortality on the 192 h following S. iniae infection, respectively, and signifi-cantly lower than 40 mL/kg group (77.55%) and control group (51.19%) (P<0.05). Base on these results, diets supplemented with 10 and 20 mL/kg chitosan solution are optimal for reducing HSI and liver stress and promoting non-special immunity and disease resistance of juvenile GIFT tilapia. Moreover, diets supplemented with 20 mL/kg chitosan solution can effectively increase feed utilization and reduce the fat deposition in serum. It is suggested that in the course of the tilapia culture, diets supplemented with 10 to 20 mL/kg chitosan solu-tion (the effective concentration of chitosan is 0.6%) can enhance healthy breeding of GIFT tilapia.