Abstract:

The effect of partially replacing fish meal in seabass diets with different soybean meal SBM.
products on the growth and apparent protein digestibility was studied. Five isonitrogenous and
isocaloric diets were formulated to contain all fish meal control diet., 21.0% solvent extracted
SBM, 27% extruded full-fat SBM, 28.5% steamed full-fat SBM and 27.5% soaked raw full-fat
SBM as substitutes for 15% fish meal in the control diet. Each diet was fed to three replicate
groups of juvenile seabass with an average initial weight of 1.26–1.37 g over a period of 10
weeks. The fish were contained in flow-through and aerated aquaria. Fish fed the control diet grew
significantly better than fish fed extruded full-fat SBM, steamed full-fat SBM or soaked raw
full-fat SBM diets, but not significantly different from that of fish fed the solvent-extracted SBM
diet. Feed efficiency and survival did not differ significantly among treatments except for fish fed
the soaked raw full-fat SBM diet. Fish fed the soaked raw full-fat SBM had significantly lower
weight gain, feed efficiency, protein efficiency and survival. Fish fed this diet also showed some
histological changes in their gastrointestinal tract. The apparent protein digestibility of diets
containing all fish meal, solvent-extracted, extruded, steamed and soaked raw full-fat SBMs were
92.8, 94.2, 92.3, 94.4 and 73.7%, respectively. The lower growth obtained in fish fed the extruded
or steamed full-fat SBM diets as compared to that of the control fish meal diet could not be
attributed to protein digestibility, but it could be due to the lower feed intake during the first two
weeks suggesting that palatability was possibly a factor. Soaked raw full-fat SBM is a poor protein
source for seabass diet. Solvent-extracted SBM is more palatable for small seabass 1.30–3.50 g.