| A ten-week feeding trial was conducted to evaluate the effects of dietary sulfur amino acids on the growth performance and amino acid metabolism of rice field eel(Monopterus albus)(30 ± 0.15)g.There are six isonitrogenous and isoenergetic diets were formulated,A positive control group(fish meal 550g/kg),a negative control group(fish meal 220g/kg,soy protein concentrate 300g/kg),and 2g/kg of taurine,methionine,cysteamine and cystine were added to the low fish meal diet,three replicates per group,and 50 fishes in each cage(2m×1.5m×1.5m).Results are as follows:Part two: Compared with positive control group,weight gain rate,visceral body ratio of rice field eel and the enzyme activity of intestinal in negative control group were decreased significantly(P<0.05),but feed conversion rate increased significantly(P<0.05).Activity of intestinal lipase in low fish meal added taurine increased significantly(P<0.05).Weight gain rate of rice field eel,enzyme activity of intestinal and the crude lipid of whole body increased significantly(P<0.05),but feed conversion rate of rice field eel decreased significantly(P<0.05).Weight gain rate of rice field eel,enzyme of intestinal and the crude lipid of whole fish increased significantly by added cysteine(P<0.05),but feed conversion rate of rice field eel decreased significantly(P<0.05).Weight gain rate of rice field eel,activity of intestinal enzyme and crude lipid of whole fish increased significantly by added cystine(P<0.05),but feed conversion rate of rice field eel decreased significantly(P<0.05).Part three: Compared with positive control group,serum glucose,LDL-C,total cholesterol,triglyceride,total protein and hepatic GPT activity were significantly decreased in negative control group(P<0.05),but serum urea nitrogen,HDL-C and hepatic GOT activity were significantly increased(P<0.05).Serum glucose,triglyceride and urea nitrogen increased significantly in low fish meal added taurine group(P<0.05),but serum GOT activity decreased significantly(P<0.05).Serum glucose,LDL-C,total cholesterol,total protein,urea nitrogen,blood ammonia and hepatic GPT activity increased significantly in low fish meal added methionine group(P<0.05).Serum total protein,urea nitrogen,blood ammonia and hepatic GPT activity were significantly increased in low fish meal added cysteine group(P<0.05),but serum HDL-C and GOT activity decreased significantly(P<0.05).Serum glucose,triglyceride,bile acid,total protein,urea nitrogen,blood ammonia and hepatic GPT activity were significantly increased in low fish meal cystine added group(P<0.05),but serum HDL-C,LDL-C and GOT activity were significantly decreased(P<0.05).In control group,the hepatic cells were healthy and the hepatic tissues were normal.Negative control group shown vacuoles in hepatic tissue,and some hepatic tissues were damaged.Adding sulfur amino acids in low fish meal diet can improved hepatic histological structure.Part four: Compared with positive control group,the serum methionine and cysteine content in the negative control group decreased significantly during 3-24 h feeding(P<0.05).After feeding of 3H,the serum methionine in taurine added group increased significantly(P<0.05),and the serum cysteine in cystine added group increased significantly(P<0.05).After feeding of 6h,the serum cysteine in methionine,cysteamine and cystine added group increased significantly(P<0.05),but the serum cysteine in taurine added group decreased significantly(P<0.05).After feeding 9h,the serum methionine in methionine added group increased significantly(P<0.05),and the serum cysteine in cystine added group increased significantly(P<0.05).After feeding 12 h,the serum methionine in methionine added group increased significantly(P<0.05),and the serum cysteine in all sulfur amino acid added group increased significantly(P<0.05).After feeding 24 h,the serum methionine in the low fish meal diet increased significantly(P<0.05).The total essential amino acid of serum in the control group,the negative control group and the taurine group reached the peak value after feeding 6h,and the total essential amino acid content in the negative control group was lower than that in the control group.The content of essential amino acids was still less than that in the control group.The content of total essential amino acids in the methionine group reached the peak after ingestion of 9h,and the highest level of 9h intake was in the methionine group.The serum total essential amino acids of cystine group reached the peak after ingestion of 12 h.Part five: Compared with positive control group,the muscle hardness,elasticity,chewiness of the negative control group and the expression of MEF2 C,MYf5 and MYOD2 were significantly decreased(P<0.05),but the expression of MEF2 D and MRF4 in muscle increased significantly(P<0.05).The expression of MEF2 A,MEF2B,MEF2 D,MYf5,MYOD2 and MYOG in low fish meal taurine added diet increased significantly(P<0.05),but the expression of MEF2 C,MRF4,Myh6 and MYOD1 genes decreased significantly(P<0.05).The expression of all muscle related genes decreased significantly in added methionine and cystine group(P<0.05).The expression of MYOD1 and MYOD2 in cysteamine added group increased significantly(P<0.05),but the expression of MEF2 A,MEF2B and MEF2 D decreased significantly(P<0.05).Conclusion: Adding sulfur amino acid in high proportion soybean protein concentrate diet can improve the efficiency of amino acid metabolism,and increased regulate of muscle myogenic factors,thus inprove the growth performance of rice field eel. |
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