Dietary Protein Requirement of Juvenile Erythroculter ilishaeformis(♀) ×Ancherythroculter nigrocauda(♂) Hybrid F_1

WU Fan;WEN Hua;LI Qing;CHEN Jian;WANG Guiying;LI Pei;SUN Yanhong;LU Xing;YANG Changgeng;Fisheries Research Institute,Wuhan Academy of Agricultural Sciences;Yangtze River Fisheries Research Institute,Chinese Academy of Fishery Sciences;Wuhan Xianfeng Aquaculture Technology company limited;

WU Fan%WEN Hua%LI Qing%CHEN Jian%WANG Guiying%LI Pei%SUN Yanhong%LU Xing%YANG Changgeng%Fisheries Research Institute,Wuhan Academy of Agricultural Sciences%Yangtze River Fisheries Research Institute,Chinese Academy of Fishery Sciences%Wuhan Xianfeng Aquaculture Technology company limited

juvenile hybrid F1;;protein;;growth;;requirement;;serum biochemical index;;digestive enzyme

This experiment was conducted to investigate the effects of dietary protein level on growth performance,whole body composition,serum biochemical indexes and digestive enzyme activities of juvenile Erythroculter ilishaeformis( ♀) ×Ancherythroculter nigrocauda(♂) hybrid F_1. Fish meal,casein and glutin were used as the protein sources to formulate 6 experimental diets containing different protein levels of 25.63%,30.28%,35.13%,40.26%,45.42% and 50.53%,respectively. A total of 630 juvenile hybrid F_1 with an average body weight of( 5.42±0.16) g were randomly assigned to 6 groups with 3 replicates per group and 35 fish per replicate. The experiment lasted for 56 d. The results showed as follow: 1) the weight gain rate( WGR) and specific growth rate( SGR) of the juvenile hybrid F_1 significantly increased as dietary protein level increasing( P<0.05),and then tended to stabilize when protein level was 35.13%. The feed conversion ratio( FCR) showed a decrease trend,and the FCR in 40.26% group was the lowest,and significantly lower than that in the first three groups( P<0.05). Protein efficiency ratio( PER) and protein productive value( PPV) in 50.53% group were the lowest,and significantly lower than those in the first four groups( P< 0.05). 2) The dietary protein level did not significantly affect the whole-body moisture and ash contents( P>0.05),but significantly affected the crude protein and crude lipid contents( P<0.05). Body protein contents in 40.26%,45.42% and 50.53%groups were significantly higher than those in 25.63% group( P<0.05),while the crude lipid content trended to decrease as the dietary protein level increasing. The lipid content in 50.53% group was the lowest,and significantly lower than that in other groups( P < 0. 05). 3) There were no significant differences in triglyceride( TG) and total cholesterol(TCHO) contents in serum among all groups(P>0.05). Serum total protein(TP)content trended to increase first and then decrease with increasing dietary protein level,that in 40. 26% group was the highest,and significanlty higher than that in other groups( P<0.05). Serum aspartate aminotransferase(AST) activity in 45.24% group was the highest,and significantly higher than that in other groups except40.26% group( P < 0. 05). Serum alanine aminotransferase( ALT) activity was increased initially,and then reached a plateau with increasing dietary protein level. The values in 45.42% and 50.53% groups were significantly higher than those in other groups( P<0.05). 4) The protease and amylase activities in the intestine and liver significantly affected by dietary protein level( P<0.05). While the lipase activities in the intestine and liver did not significantly affected by dietary protein level( P>0.05). Broken-line regression analysis shows that the optimal requirement of dietary protein for juvenile hybrid F_1,using WGR and PPV as a response criteria,are 36.43% and 38.81%,respectively.