Effects Of Thermostable Phytase Supplement On The Growth, Digestive Enzyme Activity Of Black Carp, Mylopharyngodon Piceus, And Nitrogen And Phosphorus In Water For Culturing This Carp

In this experiment black carp, Mylopharyngodon piceus, were fed with dietsprepared with two factors cross design, that is CaH2PO4 and neutral thermostablephytase. The CaH2PO4 was 0%, 0.75% and 1.5% levels respectively, and the neutralthermostable phytases were 0HYU/kg, 500HYU/kg and 1000HYU/kg respectivelyand 1000HYU/kg. The diet adding 1.5% CaH2PO4 but no phytase was used as basalgroup. The treatment of adding 0.75% CaH2PO4 and 1000HYU/kg ustable acid phytasein diet replaced to the treatment of adding 0.75% CaH2PO4 but no phytase in diet. Withthe 9 diets, the black carp had been rearing for 77 days, and then determined the weightgain, apparent digestibility, biochemical body composition, activities of intestinaldigestive enzyme, blood biochemical index of this fish and nitrogen and phosphoruscontents in the cultureing water. The results of this study were shown as the follows:1. The weight gains of black carp were significantly larger in groups which addedin 500HYU/kg and 1000HYU/kg of phytase than those in basal diet group(P<0.05).The weight gain of this fish had no significant difference among the basal group andadding 500HYU/kg or 1000HYU/kg thermostable phytase and 0.75% CaH2PO4groups(P>0.05). These results suggested that added phytase in basal diet couldenhance weight gain of black carp significantly.2. The feed coefficient deceased in adding thermostable phytase groups but hadno significant differences among all groups with the same CaH2PO4 level used(P>0.05).3. The apparent digestibilities of dry material in black carp fed with diets adding500HYU/kg and 1000HYU/kg thermostable phytase were significantly higher thanthose in basal group(P<0.05). Compared to the basal group, the apparent digestibilityof P was significantly improved in adding 0.75% CaH2PO4 and thermostable phytaseto diet groups (P<0.05). The apparent digestibilities of crude protein, crude fat, crudeash and calcium were not significantly different among all groups (P>0.05).4. Adding thermostable phytase could not influence the crude protein, crude fat, crude ash, calcium and phosphorus content in black carp body (P>0.05).5. The activity of AKP in serum of this fish was significantly lower in1000HYU/kg thermostable phytase group compared to basal group(P<0.05). Theconcentration calcium and phosphorus in serum did not changed significantly in allgroups(P>0.05).6. The protease activities of foregut in black carp fed with adding 500HYU/kg and1000HYU/kg phytase diets were significantly higher than those fed with basal diet(P<0.05). And the protease activities of foregut in fish fed with diets, which CaH2PO4level was lower to 0.75% but adding phytase instead, were significantly highercompared with those in basal group(P<0.05). The amylase activity of foregut in blackcarp in 1000HYU/kg thermostable phytase group was significantly higher than that inbasal group(P<0.05). With the same CaH2PO4 level in diet, adding thermostablephytase might improve the lipase activity of foregut of black carp(P>0.05).7. Nitrogen and phosphorus in culturing water had been determined for 15 days.The concentrations of total nitrogen or phosphorus were defined as the value of N or Pper liter water per kilogram of fish body weight (mg /L·kg-1). The results showed thatadding thermostable phytase could suppress the increase tendency of concentration ofnitrogen or phosphorus in water(P>0.05).In conclusion, under this trial conditions, adding thermostable phytase in dietscould significantly improve the weight gain, apparent digestibility of dry material andprotease and amylase activities of the black carp foregut(P<0.05). With the level ofCaH₂PO₄ lowing to 0.75% and adding thermostable phytase instead, the apparentdigestibility of P and activity of foregut protease in black carp could be significantlyimproved(P<0.05). It was suggested that adding 500HYU/kg to 1000HYU/kgthermostable phytase to diet is proper for the health and growth of black carp.