| Rainbow trout is a typical cold-water fish with the characteristics of delicious meat,fast growth,and high nutritional value.Its upper limit of water temperature is about 26℃,and the optimum water temperature is 16℃-18℃.At present rainbow trout has become the largest breeding fish and the highest yield among freshwater cold-water fish in China.As global warming becomes more severe and high density breeding mode appeares in most areas in China.High temperature in summer is the biggest threat to rainbow trout breeding.In the paper 450 rainbow trouts with consistent genetic background and healthy(203.72±8.97 g)were selected and randomly divided into three groups.The fish was fed different levels of taurine fodder.The additive amount of taurine were 0,600.0 and 1200.0 mg/kg respectively in the basic diet.After being raised at 18℃ for 30 days,the effect of taurine on growth performance of rainbow trout was investigated in this study.Then,the water temperature was slowly raised to 25℃.When the water temperature reached 25℃,serum samples and different tissues samples(heart,liver,spleen and brain)were collected.The changes of Hsp70 mRNA expression and biochemical indexes of rainbow trout were measured.The researched results were as follows:1.18℃ was suitable for raising water temperature,rainbow trout were fed with taurine of 600.0 mg/kg and 1200.0 mg/kg for one month.Compared with the control group,the taurine group rainbow trout the WGR increased by 68.70%(P<0.05)and 28.82%(P<0.05),the SGR increased by 52.44%(P<0.05)and 21.95%(P<0.05),which showed that adding appropriate amount of taurine to the basic feed could promote the growth of rainbow trout.2.18℃ was suitable for raising water temperature,rainbow trout were fed with taurine of 600.0 mg/kg and 1200.0 mg/kg for one month.Under the condition of heat stressed,the activities of total-superoxide dismutase(T-SOD),catalase(CAT),glutathione peroxidase(GSH-Px)and lysozyme(LZM)in heat stressed rainbow trout were significantly higher than the control groups(P<0.05).The contents of malondialdehyde(MDA)and glutamic oxalacetic transaminase(AST)in serum were significantly lower than the control group.This showed that the antioxidant enzyme activity of rainbow trout could be improved by adding an appropriate amount of taurine in basic feed.When the rainbow trout were stimulated by heat stressed,taurine could reduce the heat stress response of the body.3.18℃ was suitable for raising water temperature,rainbow trout were fed with taurine of 600.0 mg/kg and 1200.0 mg/kg for one month.Under the condition of heat stressed,the contents of albumin(ALB)and total protein(TP)in serum were significantly higher than those in the control group(P<0.05).It showed that adding appropriate amount of taurine in the basic feed can increase the protein anabolic capacity of rainbow trout,inhibit the protein decomposition process in the body caused by high temperature stressed of rainbow trout and ease the effects of high temperature stress.4.18℃ was suitable for raising water temperature,rainbow trout were fed with taurine of 600.0 mg/kg and 1200.0 mg/kg for one month.Compared the control group,1200.0 mg/kg taurine were added to basic feed,the gene expression of Hsp70 a and Hsp70 b in different tissues(heart,liver,spleen and brain)were significantly increased under the condition of heat stressed,and liver and brain were more sensitive to taurine.It showed that taurine could be used as an alternative additive resisting heat stressed in rainbow trout.The upregulation of Hsp70 were beneficial to the improvement of heat tolerance,so taurine could be used as an alternative additive for rainbow trout to resist heat stress. |
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