To better understand the nutritive value of the experimental soybean products, the
apparent protein digestibility and urease activities were studied. The apparent protein
digestibility was determined by using reference and test diets Wilson and Poe, 1985
The composition of the reference diet is shown in Table 2. The test diets consisted of
70% reference diet and 30% of the test ingredient. Chromic oxide 0.5% was used as an
indicator. Seabass with an average body weight of about 10 g were stocked in 45-l
aquarium at the rate of 25 fish each. Three replicate aquaria were randomly assigned to
each of the experimental diets. Fish were conditioned to both aquarium conditions and
the dietary regime for 5 days before feces collection began. Fish were fed to satiation
twice daily. Feces was collected for 2 weeks and kept in a freezer before freeze-drying.
Determination of protein and chromium contents in feed and feces was done as
previously described. The apparent digestibility of soybean protein was calculated
according to Cho et al. 1985 . Urease activities were measured by the rise in pHŽ .
Ž .AOCS, 1993 .