EFFECTS OF DIETARY PROTEIN LEVELS ON GROWTH PERFORMANCE, BODY COMPOSITION AND SERUM BIOCHEMICAL INDICES OF JUVENILE SINILABEO DECORUS TUNGTING (NICHOLS)

The study was conducted to evaluate the effects of dietary protein on condition factors, body composition and serum biochemical indices of juvenile Sinilabeo decorus Tungting (Nichols). Five isolipidic and isoenergetic diets were formulated containing 32.57%, 37.58%, 42.76%, 47.83% and 52.22%, respectively. A total of 450 juvenile S. decorus tungting with the average initial weight of (14.10±1.08) g were randomly distributed into five groups with three replicates per group containing 30 juvenile S. decorus Tungting per replicate for 60 days. The results indicated that the survival ratio (SR) and the feed conversion ratio (FCR) had no significant differences among groups (P>0.05). Protein efficiency declined with increased dietary protein levels (P<0.05). The weight gain rate (WGR) and the specific growth rate (SGR) of 52.22% group were significantly lower than those of 32.57% and 42.76% groups (P<0.05). The condition factor (CF) and the intestine length ratio (ILR) decreased with increased dietary protein levels, in which 52.22% group were significantly lower than 32.57% group (P<0.05). There was no significant difference in body chemical composition, except muscle crude protein and ash. With the increase of dietary protein level, the muscle crude protein increased. Seventeen amino acids were found in fish muscle. The contents of Met, Ile, Leu, Asp, Ser, Glu, Ala, Arg, ƩEAA, ΣDAA and ΣTAA in dorsal muscle of 32.57% group were significantly lower than those in 52.22% group. With the increase of dietary protein level, the triglyceride (TG) and very low-density lipoprotein cholesterol (VLDL-c) in serum were increased, except the 37.58% group. The optimum level of dietary protein for juvenile S. decorus Tungting is estimated to 37.58%—42.76% under the current experimental condition. Broken-line of SGR estimated that protein requirements for the maximum growth was about 42.91% for juvenile S. decorus Tungting.