APPARENT AND TRUE AVAILABILITIES OF AMINO-ACIDS FROM SEVERAL PROTEIN-SOURCES FOR FINGERLING RAINBOW-TROUT, COMMON CARP, AND RED-SEA BREAM

Apparent and true availabilities of amino acids from white fish meal ( FM), defatted soybean meal (SBM), malt protein flour (MPF), corn glute n meal (CGM), extruded SBM (ExSBM), and extruded MPF (ExMPF), were det ermined by an indirect method for fingerling rainbow trout Oncorhynchu s mykiss, common carp Cyprinus carpio, and red sea bream Pagrus major. Apparent protein digestibilities (APD) of FM (89 to 94%), SBM (90 to 93%), and MPF (81 to 84%) were almost identical in the three species t ested. However, the APD of CGM in carp (76%) and bream (79%) were lowe r than that in trout (95%). Individual apparent amino acid availabilit ies (AAAA) approximated the APD. The APD of ExSBM and ExMPF were two t o four percent higher than the unextruded SBM and MPF, respectively, w ithout any negative influences on individual AAAA. This finding sugges ts that the extrusion processing is an effective method to improve ava ilabilities of amino acids in SBM and MPF. On the other hand, relative ly large differences were recognized between the true amino acid avail abilities (TAAA) and the AAAA among certain amino acids. Thus, determi nation of TAAA may be necessary for more accurate and economical feed formulation.