Comparison of diets containing various fish meal levels on growth performance, body composition, and insulin-like growth factor-I of juvenile channel catfish Ictalurus punctatus of different strains

A 3×3 factorial experiment was conducted in flow-through aquaria to evaluate effects of diets, containing 0%, 4%, or 8% menhaden fish meal, on growth performance, body composition, and insulin-like growth factor-I (IGF-I) of juvenile channel catfish of Mississippi “normal” (MN), NWAC103 [formally known as USDA103], or USDA303 strains. Twenty fish with an average weight of 4.7±0.1 g fish (±S.D.) were stocked into each of 36, 110-l aquaria (four aquaria per treatment). Fish were fed 28%protein diets containing various levels of fish meal to approximate satiation twice daily for 9 weeks. Regardless of fish strain, fish fed diets containing 4% or 8% fish meal had higher diet consumption, final weight, and feed efficiency (FE) than fish fed an allvegetable diet. Regardless of fish meal level, NWAC103 and USDA303 channel catfish consumed more diet, gained more weight, and converted diet more efficiently than MN fish. No differences were observed in diet consumption, final weight, and FE between NWAC103 and USDA303 strains. There was an interaction in specific growth rate between fish strain and fish meal level. Specific growth rate was greater for MN fish fed diets containing 4% or 8% fish meal than fish fed the all-vegetable diet, whereas there were no differences in specific growth rate for NWAC103 and USDA303 fish fed various diets. Fillet protein was lower and fillet fat was higher for NWAC103 and USDA303 strains than for the MN strain. Plasma IGF-I levels were greater in NWAC103 and USDA303 channel catfish than in MN fish. Levels of IGF-I were similar between NWAC103 and USDA303 fish. The addition of fish meal to the all-vegetable diet for the three strains did not affect levels of IGF-I. Mean plasma IGF-I concentration was positively correlated to specific growth rate. Results from the present study indicated that the optimum inclusion level for fish meal was 4% of a soybean meal-based diet (fish meal levels higher than 8% were not evaluated in the present study). Including 4% fish meal in the diet improved the performance more for the MN strain than for NWAC103 and USDA303 strains, suggesting that a genotype-diet interaction exists in juvenile channel catfish. Performance of the NWAC103 and USDA303 channel catfish fed the all-vegetable diet was better than MN fish fed the same diet. Plasma IGF-I concentration may be a good indicator for channel catfish growth. © 2005 Elsevier B.V. All rights reserved.