Effects Of Dietary Methionine Resources On Growth Performance, Feed Utilization And Protein Metabolism Responses Of Large Yellow Croaker (Larmichthys Crocea) Juveniles

Large yellow croaker (Larmichthys crocea) is widely farmed in China.The study was conducted to investigate the effects of dietary methionine resources on growth performance, feed utilization and protein metabolism of large yellow croaker (Larmichthys crocea) juveniles. The content and results of the experiments have been presented as follows:1.Effects of dietary crystalline methionine or oligo-methionine on growth performance and feed utilization of large yellow croaker (Larmichthys crocea) juvenilesAn 8 week feeding trial was conducted to investigate the effect of dietary crystalline methionine (CMet) and oligo-methionine (OMet) on the growth performance, feed utilization and protein reaction of large yellow croaker (Larmichthys crocea) juveniles at initial mean body weight of 26.0±1.6 g. A practical diet with low fish meal (31.8%) was used as control diet (LF). The other six isnitrogenous and isolipid diets (CMet0.35, CMet0.65, CMet0.95; OMet0.35, OMet0.65, OMet0.95) were formulated with 0.35%,0.65%,0.95% CMet or OMet added in. The results showed that the methionine sources significantly affected the growth performance, feed utilization and protein reaction of large yellow croaker juveniles. The growth gain rate of fish in OMet0.95 treatment was significantly higher than that in LF treatment (p <0.05). Feed conversion ratio and protein efficiency ratio of fish in OMet0.65 and OMet0.95 treatment was significantly lower than that in LF treatment(p<0.05). Nevertheless, there was no significant difference at growth gain rate, feed conversion ratio and protein efficiency ratio of CMet or LF groups.In addition, no significant difference in survival rate and body composition was observed (P>0.05).The fish in OMet treatment showed lower hepatosomatic index than that in control treatment(P<0.05).The study indicated that, dietary OMet resulted in lower hepatosomatic index, better growth performance and feed utilization of large yellow croaker juveniles compared with CMet.2. Effects of dietary methionine resources on growth performance and feed utilization of large yellow croaker (Larmichthys crocea) juvenilesAn 8 week feeding trial was conducted to investigate the effect of dietary methionine sources on the growth performance and feed utilization of large yellow croaker(Larmichthys crocea) juveniles at initial mean body weight of 8.00±0.68 g. A practical diet with high fish meal was used as control 1 diet(HF) and another diet replacing 40% fish meal of control 1 diet with a mixture of soybean meal and wheat starch meal was used as control 2 diet(LF). The other isnitrogenous and isolipid diets (CMet0.25, CMet0.75; OMet0.25, OMet0.75; HMTBa0.25, HMTBa0.75; CoMet0.25, CoMet0.75) were formulated with 0.25%,0.75% crystalline methionine (CMet),oligo-methionine (OMet), HMTBa or coated-methionine (CoMet) added in. The results showed that the methionine sources significantly affected the growth performance and feed utilization of large yellow croaker juveniles. The growth gain rate of fish in OMet and CoMet treatment was significantly higher than that in LF treatment (p<0.05). The feed efficiency and protein efficiency ratio of fish in OMet Nevertheless treatment was significantly higher than that in LF treatment (p<0.05). Nevertheless, no significant difference in survival rate and body composition was observed (p>0.05). In addition, the fish in OMet treatment showed significantly lower hepatosomatic index than that in LF treatment.3. Effects of dietary methionine sources on protein metabolism responses of large yellow croaker (Larmichthys crocea) juvenilesAn 8 week feeding trial was conducted to investigate the effect of dietary methionine sources on the growth performance and feed utilization of large yellow croaker (Larmichthys crocea) juveniles at initial mean body weight of 8.00±0.68 g. A practical diet with high fish meal was used as control 1 diet(HF) and another diet replacing 40% fish meal of control 1 diet with a mixture of soybean meal and wheat starch meal was used as control 2 diet (LF). The other isnitrogenous and isolipid diets (CMet0.25. CMet0.75:OMet0.25, OMet0.75; HMTBa0.25, HMTBa0.75; CoMet0.25, CoMet0.75) were formulated with 0.25%,0.75% crystalline methionine (CMet),oligo-methionine (OMet), HMTBa or coated-methionine (CoMet) added in. The results showed methionine sources significantly affected the activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in livers (p<0.05).The activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in livers of OMet treatment was significantly higher than that of LF treatment(p<0.05). In descending order of activities of GOT in livers of the treatments with 0.25% methionine added in, OMet>CoMet>HMTBa>CMet In descending order of activities of GPT in livers of the treatments with 0.25% methionine added in, OMet>CoMet>CMet>HMTBa. In addition, no significantly was observed in blood ammonia,urea nitrogen, the activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in serum of each treatment.