Effect Of Dietary Taurine Level On The Growth Performance Of GIFT Tilapia Oreochromis Nilotictus And Grouper Epinephelus Coioides

The effects of different taurine levels in diets on the growth performance and free aminoacid distribution in tissues of GIFT tilapia (Oreochromis niloticus) and grouper (Epinepheluscoioides) were investigated. The results are presented as follows:1. Effects of dietary taurine levels on the growth performance and body composition of tilapiaand grouper.Three hundred tilapias were randomly divided into five groups with three replicate tanks ata stock density of twenty fish in each replicate. Tilapias were fed the diets containing differenttaurine levels of DT1(0.0%（)control group）、DT2(0.4%)、DT3(0.8%)、DT4(1.2%) and DT5(1.6%).Groupers of five dietary taurine treatments like tilapia feeding were respectively fed the diets atthe taurine levels of DG1(0.0%)（control group）、DG2(0.4%)、DG3(0.8%)、DG4(1.2%) andDG5(1.6%). The tilapias and groupers were fed for56d.(1) tilapia: With the increase in dietarytaurine level, weight gain rate and specific growth rate increased from DT1to DT3and thendecreased at DT4. Weight gain rate and specific growth rate in DT2-DT4groups weresignificantly higher than those of DT1and DT5groups (P<0.05); Compared with the controlgroup, feeding intake rate in taurine treated groups significantly increased and feed efficiencyrate, protein efficiency rate significantly decreased (P<0.05); Hepatosomatic index andviscerasomatic index in taurine treated groups were significantly higher than those in the controlgroup (P<0.05); There were no significant differences in condition factor and survival acrosstreatments(P>0.05); Compared with the control group, the body moisture contents in taurinegroups significantly decreased, but body lipid contents significantly increased. Body ash contentssignificantly lower than control group,but body protein contents of DT2and DT3groups weresignificantly higher than control group (P<0.05); Quadratic cruve analysis based on weigt gainindicated that the optimal level of taurine in tilapia diet was0.75%.(2) grouper: Weight gain rate,specific growth rate, feeding intake rate, protein efficiency rate and efficiency rate in taurinetreated groups were significantly higher than that in control group (P<0.05); Hepatosomaticindex in taurine treated groups were significantly lower than control group (P<0.05), the DG4group had the lowest hepatosomatic index and was about89.9%of control group’s. There wereno significant differences in viscerasomatic index, condition factor and survival rate between alltrial groups(P>0.05); Body protein contens and body lipid contents in taurine treated groups were significantly higher than control group(P<0.05), Body ash contents of taurine treatedgroups were all lower than control group, but there were no significant differences between alltrial groups(P>0.05); No significant differences in body moisture contents were found betweenall trial groups(P>0.05); Quadratic cruve analysis based on weigt gain indicated that the optimallevel of taurine in grouper diet was1.04%.2. Effects of dietary taurine levels on the free amino acid distribution in the tissues of tilapiaand grouper.Serum, liver, muscle and whole body fish were sampled to determine the free amino acidcontents.(1) With the increase of dietary taurine level, free amino acid contents in serum, liver,mucle and whole body fish of tilapia and grouper gradually decreased and free amino acidcontents in taurine treated groups were significantly lower than that in control group(P<0.05);(2)Taurine contents in serum, liver, mucle and whole body fish of tilapia and grouper graduallyincreased with increasing dietary taurine level, and the taurine contents in tissues and wholebody were positively correlated with the taurine contents in diets (r>0.907, P<0.05), and thevalues for these tissues of taurine treated groups were significantly higher than that of controlgroup (P<0.05).