Apparent and True Availabilities of Amino Acids from Several Protein Sources for Fingerling Rainbow Trout, Common Carp, and Red Sea Bream

Abstract

Apparent and true availabilities of amino acids from white fish meal (FM), defatted soybean meal (SBM), malt protein flour (MPF), corn gluten meal (CGM), extruded SBM (ExSBM), and extruded MPF (ExMPF), were determined by an indirect method for fingerling rainbow trout Oncorhynchus 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 tested. However, the APD of CGM in carp (76%) and bream (79%) were lower than that in trout (95%). Individual apparent amino acid availabilities (AAAA) approximated the APD. The APD of ExSBM and ExMPF were two to four percent higher than the unextruded SBM and MPF, respectively, without any negative influences on individual AAAA. This finding suggests that the extrusion processing is an effective method to improve availabilities of amino acids in SBM and MPF. On the other hand, relatively large differences were recognized between the true amino acid availabilities (TAAA) and the AAAA among certain amino acids. Thus, determination of TAAA may be necessary for more accurate and economical feed formulation.