USE OF SOYBEAN-MEAL AS PARTIAL OR TOTAL SUBSTITUTE OF FISH-MEAL IN DIETS FOR BLUE CATFISH (ICTALURUS-FURCATUS)

Two 12-week feeding experiments were conducted in aquaria with juvenil e blue catfish, Ictalurus furcatus. In experiment 1, juvenile (6 g) bl ue catfish were fed one of four isonitrogenous (34% protein) and isoca loric (10.0 kJ of digestible energy/g of diet) diets containing 13, 9, 4, and 0% menhaden fish meal. Soybean meal was added in increasing pe rcentages (48, 55, 62, and 69%) to the respective diets. Fish were fed all they would consume in 40 minutes twice daily (08:00 and 16:00). A fter 12 weeks, fish fed a diet with 13% fish meal had a significantly higher individual body weight than fish fed any of the other diets. Th ere was no significant difference (p>0.05) in body weights of fish fed the other four diets. No significant differences were found in percen tage survival, feed conversion ratio, and protein efficiency ratio amo ng treatments. In experiment 2, blue catfish (9 g) were fed one of fiv e isonitrogenous (35% protein) and isocaloric (10.5 kJ of digestible e nergy/g of fiet) diets. Diet 1 contained 15% menhaden fish meal and 42 % soybean meal. Diets 2-5 contained 0% fish meal and 69% soybean meal with various (0.0, 0.3, 0.6, and 0.9%) percentages of added L-methioni ne. Fish were fed as in experiment 1. After 12 weeks, individual weigh t, weight gain, survival, specific growth rate, and feed conversion ra tio were not significantly different (p>0.05) among treatments and ave raged 36 g, 302%, 100%, 1.6%/day, and 2.4, respectively. Whole-body co mpositions of fish were not significantly different (p > 0.05) among t reatments and averaged 61% and 27% for percentage protein and fat, res pectively. These data indicate that soybean meal can totally replace f ish meal in a diet for blue catfish without supplemental L-methionine. This may allow producers to feed more economical diets without advers e effects on growth and survival.