饲料精氨酸含量对海水驯化虹鳟的渗透调节、抗氧化和免疫力的影响

DIETARY ARGININE CONTENT ON OSMOREGULATION,ANTIOXIDANT STATUS,AND IMMUNE CAPACITY OF RAINBOW TROUT(ONCORHYNCHUS MYKISS)DURING SEAWATER ACCLIMATION

实验旨在探究饲料添加精氨酸(Arg)对虹鳟(Oncorhynchus mykiss)海水驯化前后渗透调节、抗氧化和免疫力的影响。选择初始体质量(67.04±6.93)g的虹鳟480尾,随机分为4组,分别投喂Arg含量为1.46%(A-1.46)、2.50%(A-2.50)、3.45%(A-3.45)和4.62%(A-4.62)的4种实验饲料。在淡水养殖5周后,对上述每组虹鳟分别进行为期2d(SA-2)和4d(SA-4)的海水驯化,SA-2为首日从盐度0升至15,次日升至本地海水盐度27;SA-4首日升盐同SA-2,随后每天以4/d的升盐速度至盐度27。在淡水养殖结束和入海后的1d、7d和21d采样并测定虹鳟渗透调节、抗氧化和免疫等指标。结果显示,在淡水养殖结束后,A-4.62组虹鳟末体重、增重率显著低于其他组,表明饲料Arg含量过高会使虹鳟生长受到抑制。在两种驯化方式下,随着入海时间推移,A-3.45和A-4.62组虹鳟血清K^(+)含量先升高后恢复,表明两组虹鳟离子转运能力较好;在入海后21d时,各组虹鳟肝脏总抗氧化能力(T-AOC)显著高于其相应淡水值,而A-3.45组虹鳟的综合生物标志物响应(IBR)最小,表明A-3.45组可能所受盐度胁迫较小。相比于SA-2方式,SA-4方式下各组虹鳟渗透压较平稳,表明SA-4方式更有利于虹鳟维持其渗透平衡。此外,在SA-2方式入海1d时,A-3.45组虹鳟将体内多余Na^(+)排出体外,使其更好适应海水环境;随着入海时间推移,A-3.45组虹鳟血清溶菌酶(LZM)含量显著升高,表明入海后A-3.45组的体液免疫力显著提高。在SA-4方式入海21d时,A-3.45组虹鳟降低鳃NKA活力来减少Cl^(–)流入,从而更好维持离子平衡。综上,在两种驯化方式下,饲料Arg含量为3.45%时,虹鳟的生长好,适应能力更强。

This study aimed to investigate the effects of dietary supplementation with arginine(Arg)on osmoregulation,antioxidant status,and immune capacity of rainbow trout Oncorhynchus mykiss before and after seawater acclimation.A total of 480 rainbow trout(initial weight of 67.04±6.93 g)were randomly divided into four groups.Four experimental diets were formulated to contain Arg level of 1.46%(A-1.46),2.50%(A-2.50),3.45%(A-3.45),and 4.62%(A-4.62),respectively.After five weeks of freshwater culture,each group of rainbow trout underwent seawater acclimation for 2 days and 4 days,designated as SA-2 and SA-4,respectively.SA-2 entails a gradual increase in salinity from 0 to 15 on the first day,followed by reaching the local seawater salinity of 27 on the second day.SA-4 followed a similar increase as SA-2 on the first day,then increased by 4 units per day until reaching as a salinity of 27.Samples were collected at the conclusion of freshwater culture and at 1d,7d,and 21d after seawater transfer to evaluate osmoregulation,antioxidant,and immune parameters.Results showed that at the end of freshwater culture,the A-4.62 group had significantly lower final body weight and percent weight gain,indicating that excessive dietary Arg hinder their growth.Under both acclimation conditions,serum K^(+)levels in the A-3.45 and A-4.62 groups initially increased and then normalized over time,suggesting effective ion regulation in these Arg groups.After 21d after seawater transfer,the liver total antioxidant capacity(T-AOC)of all groups significantly surpassed their respective freshwater values,with the A-3.45 group displaying the lowest integrated biological response(IBR),indicating reduced stress in this group.Compared to the SA-2 method,rainbow trout in all SA-4 groups maintained more stable osmotic pressure,suggesting SA-4’s superiority in maintaining osmotic balance.Additionally,under SA-2,the A-3.45 group excreted excess Na^(+)to better adapt in seawater;serum lysozyme(LZM)levels notably rose over time in the A-3.45 group,indicating an enhanced immune response in these rainbow trout after seawater transfer under SA-2.Under SA-2,after 21d of seawater transfer,the A-3.45 group exhibited reduced gill NKA activity to decrease Cl^(–) influx,thereby better maintaining ion balance.In summary,under both acclimation conditions,rainbow trout demonstrated enhanced growth and adaptability when dietary Arg content was 3.45%.