EFFECTS OF EXOGENOUS ENZYMES ON AMMONIA NITROGEN AND SOLUBLE PHOSPHORUS EXCRETION IN LARGE YELLOW CROAKER (PSEU DOSCIAENA CROCEA) AND JAPANESE SEABASS(LATEOLABRAX JAPONICU S)

An experiment was conducted to evaluate the effects of dietary phytase (PY) and non-starch polysaccharide enzyme(WX and VP) on ammonia nitrogen and soluble phosphorus excretion in large yellow croaker (Pseudosciaena crocea) andJapanese seabass (Lateolabrax japonicus), respectively.Using soybean meal, rapeseed meal, peanut meal, fish meal and meatand bone meal as protein sources, fish oil and soybean oil as lipid sources, lysine, methionine and valine as supplements simu-lated the essential amino acid pattern of fish meal, five isonitrogenous and isoenergetic experimental dietswere formulated to con-tain 0, 200mg/kg phytase (2500 IU per gram), 800mg/kg WX (mainly including glucanase, pentosanase and cellulosase, eachwith 50 IU per gram), 400mg/kg VP (mainly including xylanase, 1000 IU per gram), and the combination of 800 mg/kg WXand 400mg/kg VP, respectively.Each diet was randomly assigned to triplicategroups of fish, and each group was stocked with180 large yellow croaker (initial body weight, (1.88±0.02) g) or 60 Japanese seabass initial body weight, (6.28±0.1)g.Fish were fed twice daily (06: 30 and 16: 30) to satiation for 8 weeks.During the experimental period, the water temperaturefluctuated from 26.5 e to 32.5 e, salinity from 32j to 36 j and dissolved oxygen was approximately 7mg/L.After feeding for8 weeks in sea cages with experimental diets, fish from each cage (3 fishes per cage) were transferred into indoor tank (20L) todetermine ammonia nitrogen and soluble phosphorus excretion rates in starvation and satiation condition.Each tank stocked with1 large yellow croaker (12.48±1.02) g or 1 Japanese seabass (54.87? 2.34) g.The ammonia nitrogen was determined by thesodium hypobromite oxidation method.The soluble phosphorus was determined by phosphorus molybdenum bluemethod.There-sults showed that ammonia nitrogen and soluble phosphorus excretion rates of fish in starvation condition were not affected by theexperimental diets (p>0.05).However, the ammonia nitrogen excretion rates in satiation condition were significantly lower infish fed with diets supplemented with the combination of WX and VP, WX or VP than that fed with basal diet and phytase sup-plemented diet (p0.05), but therewas an upward trend of soluble phosphorus excretion rate in fish fed with phytase supplementeddiet.These findings in the present study suggested that supplementation of 200 mg phytase per kilogram diet might degrade thedietary phytate and increase availabile phosphorus absorbability, but not significant effects on ammonia nitrogen excretion rates oflarge yellow croaker and Japanese seabass.The non-starch polysaccharide enzymes (400 mg VP, 800 mg WX, or the combina-tion of 800 mg WX and 400 mg VP per kilogram diet) were effective to degrade the ant-i nutritional effect of non-starch polysac-charide and decrease ammonia nitrogen excretion rates of large yellow croaker and Japanese seabass, but not significant effects onsoluble phosphorus excretion rates of experimental fish.