| As we know,China is the largest aquaculture country in the world.With the gradual expansion of aquaculture area,the quality and demand of feed in the process of aquaculture is getting higher and higher,so the use of feed protein source is increasing.However,for a long time,the situation of lack of feed protein sources has existed in the world,and some high-quality feed protein sources such as fish meal in China mainly rely on imports.With the increasing demand for high-quality animal protein sources such as fish meal,China has become the largest importer of fish meal in the world,leading to the continuous increase in the import price of fish meal and other animal protein sources,and the situation of higher and higher costs and lower and lower benefits in the process of aquaculture.How to reduce the use of fish meal in aquatic feed has become a recognized severe problem and challenge in the entire aquatic industry.By reducing the protein level in feed or replacing fish meal,the use of fish meal can be effectively reduced with low breeding cost.However,with the decrease of protein content in feed,it will cause the imbalance of amino acid ratio,and affect the normal growth of cultured objects.Use plant-based protein sources instead of fish meal,but plant-based protein sources contain a lot of ingredients that fish can’t use.It has become a hot topic to reduce the feed protein level and improve the utilization of protein without affecting the normal growth of cultured fish.This experiment is to big sea bass as the research object,to set low protein feed and supplement the methionine and lysine and soybean meal replacement for big sea bass fish meal and add butyric acid bacteria growth performance,feed utilization,body composition and the influence of oxidation resistance,is big sea bass quality and compound feed research and provides some references for the healthy breeding.1.Effects of methionine and lysine supplementation in low protein diets on growth performance,body composition,antioxidant capacity and immune enzymes of largemouth bass(Micropterus salmoides).To investigate the effects of methionine and lysine supplementation on growth performance,transaminase,body composition and antioxidant performance of Juvenile largemouth bass(initial body weight 31.52 ± 0.62g).Three dietary protein gradients(46%(control),41%(LP1)and 36%(LP2))were set,and the corresponding crystal lysine and methionine were supplemented on the basis of 41% and 36% protein diets to keep the same content with the control group,which were recorded as LP1+AA group and LP2+AA group,respectively.Each experimental group contained 3 biological replicates and the feeding cycle was 8 weeks.The results showed as follows: there were no significant differences in weight gain rate(WGR),feed conversion ratio(FCR),specific growth rate(SGR)and protein retention(PR)in LP1+AA group compared with Control group(P>0.05),but significant changes were observed in other groups compared with Control group(P<0.05).With the decrease of protein level,crude protein content in muscle and whole body was significantly decreased(P<0.05),but there was no significant difference between LP1+AA group and Control group.There was no significant change in crude fat and ash content.The hepatosomatic ratio(HIS)in low protein diet group were significantly decreased(P>0.05),but there was no significant difference between LP1+AA group and Control group(P>0.05).Compared with the Control group,the levels of liver reactive oxygen species(ROS)and total antioxidant capacity(T-AOC)of fish in LP2 and LP2+AA groups were significantly changed(P<0.05);The T-AOC of liver in LP1 group was significantly decreased(P<0.05),but lysine and methionine supplementation significantly increased(P<0.05).Reducing dietary protein level(5% or10%)had no significant effect on liver transaminase activity(P>0.05).Although serum glutamic-pyruvic transaminase(GPT)activity in LP2 group was significantly changed(P<0.05),there was no significant difference between LP2+AA group and Control group(P>0.05).The results showed that when dietary protein content was reduced from 46% to41% and essential amino acids were supplemented,there was no significant effect on growth performance,but when dietary protein content was reduced to 36%,lysine and methionine supplementation could not effectively alleviate the negative effects of dietary protein low on growth performance.2.Effects of replacement of fish meal(FM)with Soybean meal(SM)and Addition of Clostridium butyricum(CB)on growth performance,feed utilization,body composition and antioxidant performance of largemouth bass.Objective To investigate the effects of replacing fish meal with soybean meal and adding Clostridium butyricumon growth performance,feed utilization,body composition and antioxidant performance of largemouth bass.Juvenile largemouth bass(initial body weight 50.78±1.15g)were used as the research object.Seven diets were designed.The fish meal content of control group was 30%,and soybean meal was used to replace fish meal with 25%,50% and 75%,respectively.Three groups of soybean meal were supplemented with 0.05% Clostridium butyricum.An 8-week feeding experiment was conducted,and the growth performance,feed utilization,body composition and antioxidant performance of largemouth bass were analyzed after the feeding experiment.The results showed as follows: there were no significant differences in growth performance,body composition and antioxidant capacity of largemouth bass when25% fish meal was replaced by soybean meal(P>0.05),but WGR and SGR of largemouth bass were significantly decreased(P<0.05),and FCR was also significantly increased(P<0.05).ROS,T-AOC and SOD in liver and serum were significantly changed(P<0.05).However,there were no significant differences in WGR,SGR,ROS,T-AOC and SOD in the group supplemented with Clostridium butyricumon the basis of replacing50% fish meal compared with the control group.When the replacement level reached75%,the growth performance and antioxidant performance were improved by adding Clostridium butyricum,but still significantly lower than the control group.The results showed that adding Clostridium butyricum on the basis of replacing 50% fish meal with soybean meal did not negatively affect the growth performance and antioxidant capacity of largemouth bass. |
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