The fish fed with SPKM and SMPKM diets were
superior in specific growth rate (P b 0.05) and feed conversion ratio (P N 0.05) when compared with the UPKM
treatment. The digestion capacity of fish also slightly improved with both these dietary treatments, as indicated
by the specific activities of trypsin and amylase (P N 0.05). Only the fish fed with SPKM were adapted to digest
lipids as compared to the control. Significant improvements in the radical scavenging activity of stomach were
observed with MPKM and SMPKM treatments, but the levels were unaffected in the liver and intestine. No
negative effects were found on scavenging activity in the three organs, in fish fed SPKM diet as compared to
the control. The carcass and muscle compositions were closely similar across the four dietary treatments, with
only small improvements fromthe SPKMand the SMPKMdiets in terms of carcass moisture and ash, and muscle
protein and RNA/protein ratio. No differences were observed in the enthalpy responses of muscle actin and
myosin between the four dietary treatments, but an inducible protein peak was found only in the fish fed with
SPKM. Overall, these findings indicate that water soaking or soaking followed by microwave irradiation improved
the nutritional quality of the PKM-containing diet. Practically, the simple low-cost modification bywater soaking
has wide application potential in the administration of aquafeed.