Studies On Nutritional Physiology Of Zinc And Phosphorus For Juvenile Turbot, Scophthalmus Maximus And Juvenile Japanese Flounder, Paralichthys Olivaceus

Feeding trials were conducted to investigate the nutritional physiology of minerals for the juvenile turbot,Scophthalmus maximus and juvenile Japanese flounder, Paralichthys olivaceus. The dietary requirements of zinc and phosphorus for juvenile turbot and Japanese flounder were conducted in indoor culture system. Results of the present study are presented as follows:1.An experiment was conducted to investigate the effects of dietary zinc on growth performance,body composition and tissue zinc accumulation of juvenile turbot(Scophthalmus maximus)with zinc sulfate( ZnSO4·H2O) as zinc source,by using a purified diet based on casein-gelatin as the main protein sources. The basal diet was supplemented with 0,15, 30,60,120 and 240 mg zinc per kg diet respectively and juvenile turbot[initial weight( 12.0±0.5) g]were fed 6 purified diets containing graded levels of zinc(17.41,33.04,47.42,76.83,137.96,258.62mg/kg) respectively for 8 weeks experimental period. The results showed that weight gain rate( WGR) increased significantly with increasing dietary zinc level( P<0.05) ,but no significant differences were observed among the juveniles fed the diets with equal to or higher than 137.96 mg/kg of dietary zinc( P>0.05), special growth rate( SGR) and WGR followed the same trend. The fish got the highest WGR,SGR and SR in the treatment with 137.96mg/kg of dietary zinc.The zinc accumulation contents in whole body, vertebrae, muscle and serum were significantly affected by dietary zinc level (P<0.05),however, the liver zinc contents remained comparatively stable among all groups( P>0.05). Broken-line analysis showed that the optimum dietary zinc requirement for juvenile turbot, using SGR as response criteria, was 96.52 mg zinc/kg diet, respectively.2.A feeding trial was conducted to estimate the optimum requirements of dietary available phosphorus for juvenile turbot in tanks (300L) of re-circulating system. Six practical diets were formulated to contain graded levels (0.23%, 0.37%, 0.51%, 0.64%, 0.79% and 0.93%) of available phosphorus from dietary ingredients and mono-calcium phosphate (MCP). Each diet was randomly assigned to triplicate groups of fish, and each group was stocked with 30 fish. Sleeve-fish muscle was used as the main protein sources in the semipurified experimental diets. Fish were fed twice daily (07:00 and 17:00) to satiation for 8 weeks. During the experimental period, the water temperature was controlled at 18°C±0.5°C, and salinity fluctuated from 31‰to 35‰and dissolved oxygen was approximately 7 mg/l. Specific growth rate (SGR) of turbot (initial body weight, 4.3±0.1g) increased significantly with increasing total phosphorus from 0.27% to 0.57% of diet (P<0.05), and then leveled off. The body composition analysis showed that the lipid,protein and ash was significantly affected by dietary total phosphorus (P<0.05). Survival and feed efficiency were not significantly affected by dietary total phosphorus level (P>0.05). The blood biochemistry analysis showed that plasma alkaline phosphatase (ALP) activity decreased with the increase of dietary total phosphorus levels (P<0.05). Broken-line analysis showed that the optimum dietary zinc requirement for juvenile turbot, using SGR as response criteria, was 0.51% diet, respectively.3.A feeding trial was conducted to estimate the optimum requirements of dietary available phosphorus for Japanese flounder in tanks (300L) of re-circulating system. Six practical diets were formulated to contain graded levels (0.23%, 0.37%, 0.51%, 0.64%, 0.79% and 0.93%) of available phosphorus from dietary ingredients and mono-calcium phosphate (MCP). Each diet was randomly assigned to triplicate groups of fish, and each group was stocked with 30 fish. Sleeve-fish muscle was used as the main protein sources in the semipurified experimental diets. Fish were fed twice daily (07:00 and 17:00) to satiation for 8 weeks. During the experimental period, the water temperature was controlled at 18°C±0.5°C, and salinity fluctuated from 31‰to 35‰and dissolved oxygen was approximately 7 mg/l.Specific growth rate (SGR) of Japanese flounder (initial body weight, 5.7±0.1g) increased with increasing total phosphorus from 0.27% to 0.57% of diet (P>0.05), then significantly decreased from 0.57% to 1.03% (P<0.05). The body composition analysis showed that lipid, protein and moisture was significantly affected by dietary total phosphorus (P<0.05). Survival and feed efficiency were not significantly affected by dietary total phosphorus level (P>0.05). The blood biochemistry analysis showed that plasma alkaline phosphatase (ALP) activity increased with the increase of dietary total phosphorus levels from 0.27% to 0.88% of diet (P<0.05),then decreased from 0.88% to 1.03% (P<0.05). Broken-line analysis showed that the optimum dietary zinc requirement for juvenile turbot, using SGR as response criteria, was 0.51% diet, respectively.