Study On The Utilization Of Dietary Soybean Meal Protein In Siganus Guttatus

The serious imbalance between supply and demand of fish meal has led to the high cost of artificial diet for aquic animal.It is great significance to find the suitable sources and levels of vegetable protein to replace fish meal for promoting the research on the nutritional demands of aquaculture animals and the further development of aquaculture and diet processing industries.This study focus on the future trend of the aquaculture industry development and select the economic fish Siganus guttatus as experimental fish and soybean meal as the vegetable protein source to replace fish meal,two experiments were designed to investigate the effects of different replacement level of fish meal by soybean meal and dietary supplement of exogenous methionine,taurine on growth performance,biological indicators and body composition of Siganus guttatus.The main results are as follows:?1?An 8-week feeding trial was conducted to investigate the effects of different replacement level of fish meal by soybean meal on Siganus guttatus growth performance,biological indicators and body composition and to seek optimum soybean meal replacement level of Siganus guttatus.Six iso-nitrogenous and iso-energetic diets?fish meal and soybean meal were used as protein sources,corn starch as carbohydrate sources,fish oil and soybean oil as lipid sources?were formulated with six levels of soybean meal?0%,20%,35%,50%,65%,80%?,named P1,P2,P3,P4,P5 and P6,respectively.Each diet was fed to 3 replicates of fish(22fish replicate^-1,initial weight:10.25±0.36g).In this study,the addition of soybean meal in the diet had no significant difference on the survival rate of Siganus guttatus?P>0.05?.The weight gain and specific growth rate of group P2 was the highest,significantly higher than that of group P3,P4,P5 and P6?P<0.05?,but no significant difference with group P1.The feed conversion rate and daily feed intake increased with the improvement of soybean meal substitution level,and the feed conversion rate of group P1 and P2 was the lowest,significantly lower than that of group P6?P<0.05?.Protein efficiency decreased significantly when soybean meal substitution level increased from 20%to 80%?P<0.05?.There was no significant difference in viscerosomatic index and intraperitoneal fat ratio between each treatment group?P>0.05?.With the increase of soybean meal substitution level,the hepatosomatic index gradually decreased,and the hepatosomatic index in P4,P5 and P6 groups was significantly lower than that in P1 and P2 groups?P<0.05?.The moisture,ash,crude protein and crude lipid content of whole fish in each group were not significantly affected?P>0.05?.The crude protein content in the muscle and liver of P1 group was the lowest,which was significantly lower than that of the soybean meal replacement group?P<0.05?.There was no significant difference in muscle protein content when soybean meal substitution level increased from 20%to 80%?P>0.05?.The content of crude protein in the liver of P6 group was the highest,and there was no significant difference between P6 group and P4 group?P>0.05?,but there was significant difference between P6 group and the other four groups?P<0.05?.With the increase of soybean meal substitution ratio,the content of moisture and crude lipid in the liver was significantly affected?P<0.05?.The content of crude lipid in the liver of P1 group was the highest,and that of P6 group was the lowest?P<0.05?.There was no significant difference between the other four groups and groups P1 and P2?P>0.05?.According to the broken line model based on the two indexes of weight gain rate and specific growth rate,when the substitution level of soybean meal was about 18.92%¹9.13%will obtain the highest growth of the Siganus guttatus.?2?This study was conducted to evaluate the effects of dietary exogenous essential amino acids supplementation?the protein sources were fish meal and soybean meal?on the growth performance,biological indicators and body composition of Siganus guttatus.Four iso-nitrogenous and iso-energetic diets were prepared,which were named D1?0%of soybean meal instead of fish meal?,D2?65%of soybean meal instead of fish meal?,D3?methionine 0.68%added on the basis of 65%of soybean meal instead of fish meal?and D4?taurine 1%added on the basis of 65%of soybean meal instead of fish meal?.Each diet was based on fish meal and soybean meal as protein sources,corn starch as carbohydrate sources,fish oil and soybean oil as lipid sources.Three repeated groups with 22 fish replicate?10.23±0.33g?were set for each experimental diet.Fed for 8 weeks,the results showed that addition of methionine and taurine on the basis of the soybean meal substitution level of 65%had no significant effect on the survival rate of Siganus guttatus?P>0.05?.There were significant differences in weight gain,feed conversion rate,specific growth rate,protein efficiency and dietary intake between the whole fish meal diet group and the soybean meal replacement diets group?P<0.05?.The addition of methionine and taurine increased the weight gain,specific growth rate and protein efficiency of soybean meal substitution?P>0.05?,while the feed conversion rate and daily intake showed a downward trend with the addition of methionine and taurine?P>0.05?.There was no significant difference of viscerosomatic index between the four groups?P>0.05?.The addition of methionine to soybean meal substitute diet significantly reduced the intraperitoneal fat ratio of Siganus guttatus?P<0.05?,while the addition of taurine significantly reduced the intraperitoneal fat ratio of Siganus guttatus?P<0.05?.There was no significant difference in moisture,ash,crude protein and crude lipid content between the four groups?P>0.05?.Addition of methionine and taurine had no significant effect on muscle moisture,crude protein and crude lipid content?P>0.05?.The addition of methionine significantly increased the content of moisture and crude protein in the liver of Siganus guttatus?P<0.05?,while the addition of taurine only significantly increased the level of crude protein in the liver of Siganus guttatus?P<0.05?.Methionine and taurine were added to the diet with 65%soybean meal substitution ratio,and there was no significant difference in the liver crude lipid of Siganus guttatus?P>0.05?.