Effects of different types of dietary lipids on growth and fatty acid composition of largemouth bass

The effects of feeding diets supplemented with oils of varying sources and fatty acid compositions on growth, survival, and biochemical composition of juvenile largemouth bass Micropterus salmoides were evaluated under controlled conditions in aquaria for 12 weeks. Feed-trained juvenile largemouth bass (15.7 +/- 0.6 g) were stocked into eighteen 114-L glass aquaria at 25 fish/tank and were fed one of five experimental diets (3 replicate aquaria/diet). All diets were formulated to be approximately isocaloric (4,200 kcal gross energy per kilogram) and isonitrogenous (40% crude protein), containing protein primarily from solvent-extracted fish meal and soybean meal. Each diet was supplemented with 5% oil (by weight) using lipids from various sources and with different fatty acid compositions. These included fish oil, corn oil, sunflower oil (high oleic), linseed oil, and a fungal oil (high arachidonic acid). Fish were fed twice daily to apparent satiation. At the end of the study period, there were no significant differences (P > 0.05) between treatment groups in terms of survival (98%), weight gain (595%), specific growth rate (2.2% per day), feed conversion ratio (1.5), percent protein deposited (28%), or hepatosomatic index (2.3). Whole-body proximate composition was not significantly affected (P > 0.05) by source of added lipid, but whole-body fatty acid composition showed large differences and primarily reflected the fatty acid compositions of added oils. Largemouth bass may be able to use diets containing vegetable- and animal-source lipids, which are less expensive than the previously recommended fish oil.