DIETARY LIPID UTILIZATION BY JUVENILE SUMMER FLOUNDER (PARALICHTHYS DENTATUS)

Authors: Gaylord, Thomas; SCHWARZ, MICHAEL - VIRGINIA TECH; DAVITT, GINA - VIRGINIA TECH; COOL, RYAN - VIRGINIA TECH; JAHNCKE, MICHAEL - VIRGINIA TECH; CRAIG, STEVEN - VIRGINIA TECH

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2002
Publication Date: 6/1/2003
Citation: GAYLORD, T.G., SCHWARZ, M.H., DAVITT, G.M., COOL, R.W., JAHNCKE, M.L., CRAIG, S.R. DIETARY LIPID UTILIZATION BY JUVENILE SUMMER FLOUNDER (PARALICHTHYS DENTATUS). JOURNAL OF THE WORLD AQUACULTURE SOCIETY. 2003. v.34. p.229-235.

Interpretive Summary: The ability of juvenile Summer flounder (Paralichthys dentatus) to utilize dietary fat as energy, and its affect on growth and fat deposition has not been addressed to date. Diets were formulated to provide graded fat levels of 8, 12, 16 and 20% total fat. An additional diet was included to reproduce currently available commercial diet formulations and provided 55% crude protein and 16% total fat. Juvenile summer flounder were stocked into three aquaria and fed their respective diets for12 weeks. Upon termination of the study, effects of dietary fat on weight gain, body condition indices and proximate composition were determined. Growth was not afftected by the fat level in the diet with values ranging from 136% of initial weight in fish fed the diet containing 12% fat to 149% of initial weight in fish fed the diet containing 8% fat. Feed efficiency ratio values were similarly unaffected. Fillet yield was unaltered as was the whole body composition of the fish. High levels of dietary fat did increase the fat deposition in some muscle types. These data indicate that currently available commercial feeds for summer flounder may be too high in fat and show a need for further research to determine specific and accurate nutritional information for this species.

Technical Abstract: The ability of juvenile Summer flounder (Paralichthys dentatus) to utilize dietary lipid as energy, and its affect on weight gain and body composition has not been addressed to date. Diets were formulated to provide 55% crude protein from herring meal and casein. Herring oil was added to produce diets with total lipid levels of 8, 12, 16 and 20% total lipid while providing 3.83 kcal available energy/g dry diet, except for the diet containing 20% total lipid, which supplied 4.00 kcal available energy/ g dry diet due to the high inclusion levels for protein and lipid. An additional diet was included to reproduce currently available commercial diet formulations and provided 55% crude protein and 16% total lipid supplied solely from herring meal. Juvenile summer flounder (initial weight 23 g) were stocked into triplicate aquaria in a closed, recirculating system maintained at 20 0C and fed their respective diets for12 weeks. Fish were fed a fixed percentage of their body weight each day divided into two equal feedings. Upon termination of the study, effects of dietary lipid on weight gain, body condition indices and proximate composition were determined. Weight gain was uninfluenced by the lipid level in the diet with values ranging from 136% of initial weight in fish fed the diet containing 12% total lipid to 149% of initial weight in fish fed the diet containing 8% total lipid. Feed efficiency ratio values were similarly unaffected, ranging from 0.47-0.49. Fillet yield was unaltered as was the whole body composition of the fish. High levels of dietary lipid did increase the lipid content in the finray muscle, as fish fed the diet containing 16 and 20% dietary lipid had significantly higher lipid levels in this tissue compared with fish fed the diet containing 8% dietary lipid. No apparent protein sparing effect of lipid was observed. These data indicate that currently available commercial feeds for summer flounder may be over-formulated and show a need for further research to determine specific and accurate nutritional information for this species.