Effects Of Dietary Protein Level, Lipid Level And Feeding Frequency On The Growth And Feed Utilization Of Juvenile Large Yellow Croaker, Pseudosciaena Crocea R.

Two8-week feeding trials were conducted to study the effects of dietary proteinlevel, lipid level and feeding frequency on the growth, body composition and feedutilization of juvenile large yellow croaker, Pseudosciaena crocea R. Results of thepresent study are presented as follows:1. An8-week3×2two-factorial experiment was conducted to examine effects ofdietary protein level (40,45, and50%) and feeding frequency (two times daily andone feeding daily) on the growth, body composition and protein metabolism ofjuvenile large yellow croaker [initial average weight (13.64±0.18) g] in floatingnet cages. In the present study, at40%and45%protein level, compared with fishfed two times daily, fish fed one time daily had significantly lower final weight,SGR, but higher FCE. When fish was fed two times daily, the SGR of fish fed thediet with45%protein was significantly higher than that of fish fed the40%proteindiet (P<0.05), but no significant difference in SGR was observed between fish feddiet with50%protein diet and fish fed diet with45%protein diet (P>0.05).However, when fish was fed once daily, SGR of fish fed the50%protein diet wassignificantly higher compared to the40%protein diet and45%protein diet(P<0.05). Regardless of feeding frequency, higher dietary protein level led tosignificantly higher whole body protein and significantly lower body lipid content(P<0.05). Dietary protein level and feeding frequency both had no significanteffects on hepatosomatic index (HSI), viscerosomatic index (VSI), alanineaminotransferase (ALT) and aspartate aminotransferase (AST)(P>0.05).Significantly higher activity of liver ALT and AST were observed in higher dietaryprotein level group at each feeding frequency treatment (P<0.05). Feeding frequency had no significant effect on liver ALT and AST (P>0.05). Regardless offeeding frequency, higher dietary protein level led to significantly higher liver ALTand AST (P<0.05). Significant interactions between effects of dietary protein leveland feeding frequency were found on the growth and FCE of juvenile large yellowcroaker (P<0.05), but not on the HSI, VSI, CF, body composition and the activityof ALT and AST in serum and liver (P>0.05).2. An8-week3×2two-factorial experiment was conducted to examine effects ofdietary lipid level (9,12, and15%) and feeding frequency (two times daily and onefeeding daily) on the growth, body composition and fat deposition of juvenile largeyellow croaker [initial average weight (13.57±0.33) g] in floating net cages. In thepresent study, compared with fish fed once daily both, fish fed two times daily hadsignificantly higher final weight, SGR, but lower FCE at each dietary lipid level(P<0.05). Dietary lipid level only had a significant effect on the FCE (P<0.05).When fish were fed two times daily, no significant difference was observed in theSGR and FCE among dietary lipid level (P>0.05). However, SGR and FCE of fishfed once daily increased significantly with the increase of dietary lipid contents(P<0.05). Compared with fish fed once daily, fish fed two times daily hadsignificantly lower body moisture, but higher body crude lipid contents (P<0.05) ateach dietary protein level. Body crude lipid contents of fish fed two times dailyincreased significantly with the increase of dietary lipid contents (P<0.05), butthere was no significant difference in the body crude lipid contents of fish fed onedaily among different dietary lipid levels (P>0.05). Compared with fish fed oncedaily, fish fed two times daily had significantly higher liver and muscle lipidcontents (P<0.05). No significant difference was observed in HSI and VSI amongdifferent dietary lipid levels (P>0.05). Different dietary lipid level had significanteffects on lipid contents in liver and muscle, HSI, and VSI (P<0.05). When fishwere fed two times daily, lipid contents in liver and muscle, HSI, and VSIincreased significantly with the increase of dietary lipid level (P<0.05); However,there was no significant difference in lipid contents of liver and muscle, HSI, andVSI among dietary lipid level when fish fed once daily (P>0.05). Significant interactions of dietary lipid level and feeding frequency were only found in growth,FCE of juvenile large yellow croaker (P<0.05), but not in HSI, VSI, bodycomposition and lipid contents in liver and muscle (P>0.05).