|Rawles, Steven - Steve|
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2005
Publication Date: 5/31/2006
Citation: Subhadra, B., Lochmann, R., Rawles, S.D., Chen, R. 2006. Effect of dietary lipid source on the growth, tissue composition and hematological parameters of largemouth bass (Micropterus salmoides). Aquaculture. 255:210-222. Interpretive Summary: Commercial production of largemouth bass (LMB) is increasing due to growing demand in ethnic food markets. Fish diets contain significant amounts of expensive fish oil because fish must be provided with certain highly unsaturated fatty acids (HUFAs) that can only come from the diet. Reducing the amount of fish oil in fish diets would reduce the cost of feed but could compromise production goals and fish health. We fed largemouth bass practical diets that differed only in the oil/fat source. Some diets contained mostly fish oil as the fat source while other diets replaced different amounts of fish oil with canola or poultry fat. None of the measurements of production (weight gain, survival, feed intake, feed conversion, and protein efficiency ratio) differed in fish fed the different test diets regardless of oil/fat in the diet. Fillets from fish fed diets with fish oil had more fat than fillets from fish fed diets containing canola oil or poultry fat. The fat (fatty acid) profiles from fillets of fish fed the different diets were considered healthy because of their low indices of atherogenicity (IA) and thrombogenicity (IT). There were no differences in most of the measures of immune function in the fish fed the different diets. Therefore, replacing fish oil with alternate oil/fat sources can reduce the cost of largemouth bass diets with few negative effects for at least a quarter of the production cycle of largemouth bass.
Technical Abstract: We conducted a 12-wk feeding trial with largemouth bass (LMB) fed practical diets differing primarily in lipid source. We reduced the fish oil content of menhaden fishmeal to 0.5-1.2% by solvent extraction, and used it as the primary protein in all test diets. Diets were supplemented with 10% lipid as canola (CAN), poultry (CHK), menhaden fish oil (MFO) or CHK+MFO (50/50%). A diet containing non-extracted fishmeal (NEF)+10% CHK (NEF+CHK), and a commercial trout diet were also included. Weight gain, survival, feed intake, feed conversion ratio, and protein efficiency ratio of LMB did not differ with respect to fish fed the test diets. However, weight gain was higher in fish fed the commercial trout diet. Muscle lipid of fish fed the MFO diet was higher than that of fish fed the other diets. Muscle lipid also was higher in fish fed the commercial diet. The n-3:n-6 ratio was higher in muscle and liver of fish fed the commercial diet. Some highly unsaturated fatty acids (22:6n-3 and 20:4n-6) were conserved in fish fed diets without HUFA, but eicosapentaenoic acid (20:5n-3) declined sharply. The indices of atherogenicity (IA) and thrombogenicity (IT) of fish fed all diets were considered healthful. There were no differences in most immune function and blood parameters measured in fish fed the test diets; however, fish fed diets with MFO or CAN had higher alternative complement activity. Therefore, replacing fish oil with alternate lipid sources can reduce diet cost with few deleterious effects for at least a quarter of the production cycle of largemouth bass.