Effects Of Dietary Protein And Lipid Levels On Growth,Body Composition And Feed Utilization On Juvenile Kelp Grouper (Epinephelus Moara)

The kelp grouper?Epinephelus moara?is an emerging aquaculture species in China.Our study were conducted the effects of different dietary protein and lipid levels on the growth body composition and feed utilization of juvenile kelp grouper.The results are summarized as follows:1.Effects of different dietary protein levels on the growth,body composition and feed utilization of juvenile kelp grouperDietary protein requirement of juvenile kelp grouper Epinephelus moara was investigated through a feeding trial.Experimental diets with graded crude protein?CP?levels?33.01%,38.54%,45.21%,50.71%,56.10%and 63.09%of dry matter,respectively?were formulated.Six triplicate groups of fish?20 individuals per replicate with initial mean weight 6.00±0.10g?were fed with each diet for eight weeks.Best growth performance of fish was detected in 56.10%CP diet.The specific growth rate?SGR?significantly elevated with increasing dietary crude protein level to 50.71%,but there was no significant difference thereafter?P<0.05?.The feed conversion ratio?FCR?decreased significantly with dietary CP levels from 33.01%to 56.10%?P<0.05?.Glucose?GLU?and total protein?TP?concentrations in plasma had an increasing trend with dietary protein increasing.In the 33.01%CP group,plasma triglyceride?TG?content was significantly higher(1.67mmol L^-1)than that in other dietary treatments(0.65 to 1.14 mmol L^-1).The lowest alanine transaminase?ALT?activity was observed in the 56.10%CP group(163.16 U L^-1).Crude lipid content in the muscle and liver was significantly elevated with increasing dietary protein levels?P<0.05?.The glycogen content in the liver decreased significantly as CP levels increased?P<0.05?.The fish fed diet with higher CP level?56.10%and 63.09%?had significantly higher energy retention?ER?and lipid retention?LR?than other treatments.Based on the broken-line regression analysis of SGR and FCR,the optimal dietary protein requirement for juvenile kelp grouper is 54.61%to 56.22%.2.Effects of different dietary lipid levels on the growth,body composition and feed utilization of juvenile kelp grouperThis study aimed to estimate the effects of different level of lipid on growth performance,feed utilization and body composition by juvenile kelp grouper.Experimental diets with graded crude lipid levels?2.82%,5.30%,7.83%,11.76%,14.19%and 16.32%of dry matter,respectively?were formulated.Six triplicate groups of fish?20 individuals per replicate with initial mean weight 5.87±0.09g?were fed with each diet for eight weeks.With the increase of dietary lipid content,the weight gain?WG?improved progressively and then reach the maximum value in 7.83%dietary lipid treatment,but further increase of dietary lipid level resulted in a decreased growth performance?P<0.05?.A similar reaction was seen in the feed efficiency?FE?.The plasma glucose?GLU?concentration reduced in the fish when dietary lipid elevated with carbohydrate decreasing?P>0.05?.And the total cholesterol?T-CHO?concentration in the plasma was positive correlated to dietary lipid?P>0.05?.Both linear and quadratic responses were detected in the moisture and lipids contents of dorsal muscle,liver and the whole body to dietary lipid levels?P<0.05?.In addition,significant increases in daily lipid intake?DLI?,daily lipid gain?DLG?,daily energy intake?DEI?,and daily energy gain?DEG?were found by increment of dietary lipid level?P<0.05?,but the lipid retention?LR?decreased?P<0.05?.Both energy retention?ER?and nitrogen retention?NR?maximum were appeared in 7.82%CL treatment.According to the second-order polynomial regression analysis of WG and FE,the optimal dietary lipid level of juvenile kelp grouper is about 8.89%¹0.19%.