Effect of solvent extracted soybean meal and full-fat soya on the protein and amino acid digestibility and body amino acid composition in rainbow trout (Oncorhynchus mykiss)



 This study was carried out to investigate the apparent digestibility
coefficients (ADCs) value of protein, amino acid and energy and body amino acid
composition of rainbow trout fed
solvent extracted soybean meal (SBM) and full-fat soybean meal (FFS) partly
replacing fish meal (FM) in diets. Five iso nitrogenous (average 50.36% crude
protein) and energetic (4294 kcal/kg total energy) diets were designed in 5
groups in triplicates. Diet one as control group with 43% FM and 25% SBM, Diet
2 with 28% FM and 40% SBM, Diet 3 with 13% FM and 55% SBM, Diet 4 with 28% FM
and 40% FFS, Diet 5 with 13% FM and 55% FFS. Diets were fed to trout fishes with
49 g initial
body weight for 20 weeks at 8.8±0.45 ºC. It was found that ADCs of energy,
protein and most amino acids particularly methionine and lysine and fish body
muscle lysine levels, significantly decreased by increasing the amount of FFS
and SBM in diets (P < 0.05). On the other hand, valine, isoleucine, threonine,
methionine, phenylalanine, lysine and histidine showed a decreasing tendency
with the increasing proportion of SBM in fish body composition. It was concluded
that increasing the SBM and FFS percent replacing FM in trout fish diet, caused
reducing protein, amino acid and energy digestibility, compared with the
control diet. However, it can also be concluded that the replacement of SBM was
more efficient than the replacement of FFS as regarding growth, ADCs of protein
and essential amino acid contents of O. mykiss.