β-葡聚糖对杀鲑气单胞菌感染后虹鳟应激过程的调节作用

摘要

为研究不同浓度的β-葡聚糖对感染杀鲑气单胞菌(Aeromonas salmonicida)的虹鳟(Oncorhynchus mykiss)应激过程的调节作用, 在虹鳟饲料中添加不同浓度的β-葡聚糖(0, 0.05%, 0.1%, 和0.2%), 投喂42 d后感染杀鲑气单胞菌, 在感染后第2, 4和6天取样检测血清应激指标的变化, 第7天时统计虹鳟的存活率.结果表明, 添加β-葡聚糖能显著提高感染杀鲑气单胞菌后虹鳟的存活率, 其中0.2%剂量的保护效果最好(P<0.05).感染后第4天 β-葡聚糖组的血清总蛋白(total protein, TP)浓度显著高于对照组(P<0.05).0.1%和0.2%组的血清丙二醛(malondialdehyde, MDA)活性在感染后第2天达到峰值, 早于0.05%和对照组.0.1%和0.2%组血清髓过氧化物酶(myeloperoxidase, MPO)活性在感染后显著上升, 而0.05%和对照组却显著下降(P<0.05).β-葡聚糖组在感染后血清乳酸脱氢酶(lactic dehydrogenase, LDH)活性一直显著低于对照组(P<0.05).β-葡聚糖组血清甘油三酯(triglycerides, TG)和总胆固醇(total cholesterol, TCH)感染后下降程度显著低于对照组(P<0.05).感染后第4天, β-葡聚糖组的血清尿素氮(urea nitrogen, BUN)浓度显著低于对照组(P<0.05).总胆红素(total bilirubin, T-BIL)浓度在感染后显著下降(P<0.05), 其中0.2%组下降幅度最小.各组肝脏和脾脏热休克蛋白70基因(heat shock protein 70, HSP70)表达量在感染后都显著升高(P<0.05), 0.1%和0.2%组表达峰值出现时间早于其他组, 且其峰值高于其他组峰值.综上所述, 本实验中, 添加β-葡聚糖能显著提高感染杀鲑气单胞菌的虹鳟的存活率和有效减弱细菌感染引起的机体应激反应,其中 0.2%剂量的保护效果最好且对应激过程的减弱效果最明显(P<0.05).%In recent years, immunostimulants have become a new research field in aquaculture. β-glucan is one of the most important immunostimulants, which can enhance the body's resistance to infection by improving the non-specific and cellular immunity of animals. The present study evaluated the effects of different dietary β-glucan dosages(0,0.05%,0.1%,and 0.2%)on the anti-infection ability of rainbow trout(Oncorhynchus mykiss) after 42 days of feeding.Thereafter,rainbow trout were infected with Aeromonas salmonicida and sampled on the 2nd, 4th, and 6th days post-infection. Survival rates as well as the regulatory processes of serum stress-related factors were analyzed. Survival rates in the β-glucan groups increased significantly compared with those in the control group after A.salmonicida infection,with the 0.2% group showing the best effect(P<0.05).On the 4th day after infection, the serum total protein concentrations in all β-glucan groups were significantly higher than those in the control group (P<0.05). Serum malondialdehyde activity in the 0.1% and 0.2% groups reached a peak on the 2nd day post-infection, which was earlier than in the other infected groups. The activity of serum myeloperoxidase in the 0.1% and 0.2% groups increased significantly after infection, whereas in the 0.05% and control groups, it decreased significantly (P<0.05). The activity of lactate dehydrogenase in all β-glucan groups after infection was significantly lower than that in the control group (P<0.05). Serum triglyceride and total cholesterol levels in all β-glucan groups increased more obviously than those in the control group(P<0.05).On the 4th day after infection, the serum urea nitrogen concentration in all β-glucan groups was markedly lower than that in the infected control group (P<0.05). Total bilirubin (T-BIL) concentration decreased significantly after infection; however, T-BIL in the 0.2% group was clearly higher than that in the other groups.After infection,HSP70 expression in the liver and spleen in all groups increased significantly. In the 0.1% and 0.2% groups, it reached a higher peak earlier than in the control group. Overall, the liver and head kidney in rainbow trout were damaged to a certain extent after in-fection with A.salmonicida;however,β-glucan can effectively protect fish from damage caused by A.salmonicida, with 0.2% β-glucan showing the best effect.