The effects of four modified diets (gamma-irradiated, microwave-irradiated, probiotic-supplemented and
carbohydrase-supplemented diets) were studied on digestive enzyme specific activities and growth performance quality of juvenile Siamesefightingfish (Betta splendensRegan, 1910) during 2 weeks of critical and
intensive rearing period. The modified procedures did not change biochemical compositions and gross energy
of diets, but generally resulted in relatively higher invitro digestibilities of protein and carbohydrate and
fish survival rate, albeit insignificant. Only gamma irradiation significantly increased in vitro protein digestibility of the diet, and microwave irradiation increased starch gelatinization and water solubility (Pb0.05).
Fish fed microwave-treated diet showed highest values in all studied growth indicators and digestive
enzyme specific activities (except lipase), with significantly higher amylase specific activity and activity
ratio of amylase to trypsin (A/T ratio). Correlation analysis indicated significant relationships (Pb0.05) among
the levels of total protease, amylase and trypsin, and between SGR and A/T ratio. Muscle and body compositions
of juveniles fed on microwave- or gamma-irradiated diets were similar to the control, while the juveniles fed on
probiotic- or carbohydrase-supplemented diets showed lower protein depositions (Pb0.05). Similar levels of
RNA, RNA/Protein ratio, and Protein/Lipid ratio in body and muscle in all dietary groups fed ad libitum suggested
that the improved growth performance in juvenile Siamesefightingfish fed on microwave-irradiated diet may
not be only due to improved physicochemical properties of the diet but also improvedfish consumption rate.