Effects of different modified diets on growth, digestive enzyme activities and muscle compositions in juvenile Siamese fighting fish (Betta splendens Regan, 1910)

摘要

The effects of four modified diets (gamma-irradiated, microwave-irradiated, probiotic-supplemented andcarbohydrase-supplemented diets) were studied on digestive enzyme specific activities and growth performancequality of juvenile Siamese fighting fish (Betta splendens Regan, 1910) during 2 weeks of critical andintensive rearing period. The modified procedures did not change biochemical compositions and gross energyof diets, but generally resulted in relatively higher in vitro digestibilities of protein and carbohydrate andfish survival rate, albeit insignificant. Only gamma irradiation significantly increased in vitro protein digestibilityof 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 digestiveenzyme specific activities (except lipase), with significantly higher amylase specific activity and activityratio of amylase to trypsin (A/T ratio). Correlation analysis indicated significant relationships (Pb0.05) amongthe levels of total protease, amylase and trypsin, and between SGR and A/T ratio. Muscle and body compositionsof juveniles fed on microwave- or gamma-irradiated diets were similar to the control, while the juveniles fed onprobiotic- or carbohydrase-supplemented diets showed lower protein depositions (Pb0.05). Similar levels ofRNA, RNA/Protein ratio, and Protein/Lipid ratio in body andmuscle in all dietary groups fed ad libitumsuggestedthat the improved growth performance in juvenile Siamese fighting fish fed on microwave-irradiated diet maynot be only due to improved physicochemical properties of the diet but also improved fish consumption rate.