Effect of dietary replacement of fish meal protein with soybean meal protein on the growth, body composition and hematology indices of Schizothorax prenanti

This experiment was conducted to study the effect of replacement of fish meal by soybean meal protein on the growth ,body composition and hematology indices of juvenile Schizothorax prenanti. Healthy S. prenanti with the initial weight (14.67±0.51) gwere randomly divided into six groups with three replicates of 30 fish. Six isonitrogenous and isoenergetic diets were formulated to contain different levels of soybean meal based upon the basal diet to replace fish meal protein 0 (A1), 20% (A2), 40%(A3), 60%(A4), 80% (A5) and 100%(A6). The experiment lasted for 45 days. The results showed that the weight gain ratio(WGR), the specific growth ratio(SGR) and protein efficiency ratio(PER) were highest(118.08%, 1.95%/d, 207.22%, respectively ), the feed conversion ratio (FCR) was the lowest(1.27) when the replacement ratio of fish meal protein by soybean meal was 60%(P<0.05). The WGR, SGR, PER were significantly lower when the replacement ratio of fish meal protein of 100% ,while the FCR was significantly higher than that of the other groups(P<0.05).Based on quadratic regression analysis,the best replacement ratio of fish meal protein by soybean meal was 34.25%-45.46%.There were no significant difference in whole body moisture, crude ash and the condition factor(CF) with the replacement ratio of fish meal protein by soybean meal increased, the crude protein in whole body was highest(15.53%) when the replacement ratio of fish meal protein by soybean meal was 60%. The crude protein and lipid in whole body had no significant difference when the replacement ratio of fish meal protein by soybean meal was less than 80%(P>0.05). while the hepatopancreas somatic index(HIS) increased as soybean meal protein ratio increased, but there were no significant differences when the replacement ratio of fish meal protein by soybean meal was 0-80%(P>0.05). Superoxide dismutase(SOD) activities have a certain fluctuation as soybean meal protein ratio increased,at the same time, SOD activities were highest when the replacement ratio of fish meal protein by soybean meal was 40%. Lysozyme(LSZ) activities were gradually increased when the replacement ratio of fish meal protein by soybean meal was 20%-60%(P>0.05). The aspartate aminotransferase(AST)and alanine aminotransferase (ALT)activities increased as soybean meal protein ratio increased, but there were no significant differences when the replacement ratio of fish meal protein by soybean meal was less than 80%(P>0.05).The AST and ALT activities were significantly higher than the control group and other experimental groups(P<0.05). Results of above show that a certain percentage soybean meal protein ratio in diet could promote the growth, and improve feed protein metabolism and immunity of S. prenanti.In conclusion, the maximum replacement ratio of fish meal protein by soybean meal was 80% in the diets of S. prenanti, and the most suitable replacement ratio of fish meal protein by soybean meal was 34.25%-45.46%.