饲料中添加肽聚糖对大黄鱼生长和非特异性免疫力的影响

Effects of dietary peptidoglycan on growth and non-specific defence of Pseudosciaena crocea

以初始体重（30．8±1．33）g的大黄鱼（Pseudosciaena crocea）为研究对象，探讨饲料中添加肽聚糖对其生长和非特异性免疫力的影响。分别向每千克基础饲料中添加0（对照组）、100、500mg肽聚糖，配制出3种等氮等能的实验饲料，进行为期8周的摄食生长实验。实验在海水浮式网箱（1．5m×1．5m×2．0m）中进行，每个处理设3个重复，每个重复放养40尾。实验采取饱食投喂方式，每天投喂2次（05：00和17：30），实验期间海水水温为27．5—30．5℃，盐度为29—33，溶解氧含量在7mg·L^-1以上。饲喂实验结束后测定实验鱼的生长及相关的免疫学指标，同时每网箱取10尾实验鱼转入室内300L水族箱内进行攻毒实验。实验结果表明，饲料中添加肽聚糖显著影响大黄鱼的成活和生长。当饲料中添加100和500mg·kg^-1肽聚糖时，成活率（分别为95．8％和95．0％）显著高于对照组（88．3％）。当饲料中添加100和500mg·kg^-1肽聚糖时特定生长率（分别1．44％·d^-1和1．41％·d^-1）显著高于对照组（1．12％·d^-1）（P〈0．05）。饲料中添加肽聚糖实验组大黄鱼血液白细胞吞噬活力和血清溶菌酶活力显著高于对照组（P〈0．05），且添加肽聚糖的两实验组之间差异不显著；而血清替代补体途径活力则随着饲料中肽聚糖添加水平的增加而显著提高（P〈0．05）。哈维氏弧菌攻毒实验结果表明，饲料中添加肽聚糖实验组的累积死亡率（分别为25．0％和25．7％）显著低于对照组（64．3％）（P〈0．05）。因此，饲料中添加适宜含量的肽聚糖可显著提高大黄鱼生长率和非特异性免疫力，肽聚糖可以作为一种安全高效的口服免疫增强剂应用于大黄鱼的养殖生产。

A feeding experiment was conducted to examine the effects of dietary peptidoglycan on growth, non- specific immunity and disease resistance for large yellow croaker, Pseudosciaena crocea. The basal diet was supplemented with 0, 100 and 500 mg·kg^-1 peptidoglycan, respectively, to formulate three experimental diets. Each diet was fed to triplicate groups offish in seawater floating cages （1.5 m×1.5 m×2.0 m）, and each cage was stocked with 40 fish （with initial weight of 30.8±1.33 g）. Fish were fed twice daily （05：00 and 17：30） to apparent satiation for 8 weeks. The water temperature fluctuated from 27.5 to 30.5 ℃, the salinity from 34 to 35%0 and dissolved oxygen content was approximately 7 mg·L^-1 during the experimental period. Results showed that survival and growth were significantly （P 〈 0.05） affected by dietary peptidoglycan. Fish fed diets with 100 and 500 mg·kg^- 1 peptidoglycan supplementation had significantly （ P 〈 0.05） higher survival （95.8 % and 95.0%） than the control group （88.3%）. Specific growth rate （SGR） in fish fed the diets with peptidoglycan （ 1.44%·d^- 1 and 1.41%·d^-1, respectively） was significantly （ P 〈 0.05） higher compared with the control group （1.21% ·d^-1）. Phagocytic index （PI） and lysozyme activity （LA） of fish fed the diets with peptidoglycan were also higher than those of control group, and there were no significant （ P 〉 0.05） differences between two peptidoglycan supplementation groups. However, altemative complement pathway activity （ACH50） significantly （P 〈 0.05） increased with increasing dietary peptidoglycan. The results of Vibrio harveyi challenge showed that the fish fed diets with peptidoglycan supplementation had significantly lower cumulative mortality （25.0% and 25.7%, respectively） than the control group （64.3%）. The results suggested the dietary peptidoglycan significantly improved the growth, non-specific immunity and disease resistance of large yellow croaker. Therefore, peptidoglycan could become a safe and efficacious immunostimulate supplemented to the diets for large yellow croaker.