Lipid Requirement And Fishmeal Replacement In Diets Of Large Yellow Croaker, Pseudosciaena Crocea R.

In order to investigate the optimum requirement of dietary lipid for large yellowcroaker two feeding trials were proceeded at two different growth stages. Experimentson the survival, growth, body composition, digestive enzyme activity and tissuestructure were conducted and the results are as following;1. The effects of replacement of fish meal FM by soya bean meal SBM on thesurvival, growth, body composition and activity of some digestive enzymes wasinvestigated during a60days growth experiment for large yellow croaker(Pseudosciaena crocea R). Five isonitrogenous (42%crude protein) and isolipic(13%DM) diets were formulated replacing0,35%,40%and45%FM by SBMprotein（named as PP00,PP35,PP40,PP45）. The100%frozen trash fish （FTF）diet and the PP00diet were used as control. Each dietary treatment was tested intriplicate groups of180fish (initial weight of10.57±0.43g) stocked in seafloating cage (1.5m×1.5m×2m) arranged with a density of60fish per tank in acompletely randomized design. Fish were fed twice per day at a feeding rate of3%of biomass. There were no significant differences in the survival and specialgrowth rate (SGR) among the fish fed the diets with0(the control group),15,30and45%protein from SBM. The digestibility experiment showed that the liverlipase activity were significantly higher in the groups feed with diet replaced bySBM compared with those feed with diet containing FM (P0.05). However,trypsin activity was found decreased in the group fed with SBM. The histologicalstudy reveled that the dietary of the40and45%of SBM protein damage theultrastructure of the liver and the intestine. The FM replacement by SBM at thelevel of35%don’t affect the survival and the growth of the large yellow croakereither damage the tissue structure and then can be considered as an optimum replacement level.2. As second experiment we propose to determine the dietary lipid requirement ofthe large yellow croaker through a growth trial. Purified diets with six dietarylipid levels (3%,6%,9%,12%,15%and18%named as L3,L6,L9,L12,L15andL18) were each fed to triplicate groups of juvenile fish (mean initial weight10.57±0.43g g) and adult (mean initial weight194.65g±2.31g) stoked in a sea floatingcage for60days and71days respectively. Weight gains was highest (P <0.05) infish fed diets with3–11%lipid for the juvenile’s fish group and with3–12%lipid for the adult fish group and insignificantly decrease on further lipid level.The use of a diet containing more than9%resulted in a significant decrease inpercentage body composition content (BCC)(protein, moisture and ash) in thecarcass of the juvenile’s group, whereas juvenile’s fish fed diets containinggreater amounts of lipid showed an increase in carcass.No significant change inthe BCC was reported for the adult group. Both the high-density lipoproteincholesterol (HDL-C) and the low-density lipoprotein cholesterol (LDL-C)increase significantly with the increase of the lipid level in the juvenile’s group.Meanwhile, only the (HDL-C) follow the same pattern then in the juvenile’sgroup. According to this data the optimum lipid level was recorded in fish fedwith11%for the juvenile’s group and12%lipid diet for the adult group.