| Three experiments were conducted to study the effects of utilization of acidic micro-phytase in vegetable protein based on diet of non-stomoach fish species, gibel carp (Carassius aruatus,gibelio). Firstly, survial rate of phytase under cold pelleting, steam pelleting and extrusion conditions were deterimined, respectively. Two growth trials were designed to study the effect of replacement mono-calcium phosphate with acidic phytase on the growth performance, feed efficiency ratio, body composition, nutrient retention and excretion and bone development of gibel carp.(arassius aruatus,gibelio).Experiment 1 was conducted to study the effects of three different feed processing methods (cold pelleting process, steam pelleting process and extrusion process) on phytase activity. The results showed that extrusion might totally killed phytase with high processing temperature of above 120℃. After steam pelleting processing (90℃), 65% and 22.3% of phytase activities were reserved for thermal-stable phytase and common phytase, respectively. Besides, 76% of common acidic phytase activity could be reserved after cold pelleting process (60~66℃). Accordingly, from low to high, the activity ratio reserved under different feed processing technology were extrusion process, steam pelleting process, and cold pelleting process.After the experiment 1, the experiment 2 was conducted to evaluate effects of acidic phytase on the growth performances and the metabolism of phosphorus of gibel carp (Carassius aruatus, gibelio, initial body weight 5.14±0.01g) fed with vegetable protein based diets. Seven experimental diets Control,PE250,PE275,PE2T,PE550,PE575,PE5T were formulated to contain 2000FTU/kg or 5000FTU/kg acidic phytase to replace 0%, 50%, 75%, 100% Ca(H2PO4)2, respectively, and the control diet contains 21mg/kg Ca(H2PO4)2, and another diet was PEHT, which contained 1500FTU/kg high thermal-stability of phytase to replace 100% Ca(H2PO4)2. Four replicates were designed for each diet and 50 fish were batch-weighted in each tank in a recirculating system for 8 weeks. The results showed that control diet was significantly better than other diets on growth performance, body composition and bone development. With higher acidic phytase replacement level, growth performance, feed efficiency ratio and phosphorus utilization were significantly decreased(P<0.05), while condition factor was significantly increased (P<0.05). Phytase content in diets at 2000FTU/kg and 5000FTU/kg did not significantly affect the growth performance. There were no significant effects on apparent digestibility coefficients (ADC) of dry matter and protein among all diets(P>0.05), but ADC of total phosphorus of Control,PE250 and PE550 groups were significantly higher than that of other group(sP<0.05). And the growth performance and feed utilization of PEHT was the worst. Meanwhile, there were no significant difference on Hepaticsomatic index(HSI)and serum calcium and phosphorus among groups (.P>0.05). In Experiment 3, according to the results from experiment 2, five experimental diets Control, PE220, PE230, PE240, PE250 were formulated to contain 2000FTU/kg acidic phytase to replace 0%, 20%, 30%, 40%, 50% Ca(H2PO4)2, respectively. While the other five experimental diets ControlA,PE220A,PE230A,PE240A,PE250A were formulated to contain 2000FTU/kg acidic phytase and 0.3% acidifier to replace 0%, 20%, 30%, 40%, 50% Ca(H2PO4)2, respectively. Both of Control and ControlA diets contain 21mg/kg Ca(H2PO4)2. Four replicates were designed for each diet and 23 fish were batch-weighted in each tank in a recirculating system for 8 weeks. The results showed that diets with 0.3% acidifier could increase the FBW, SGR, PER, PRE, serum calcium and phosphorus, but decrease FCR, though there was no significant difference with no acidifier diets(P<0.05). There were no effects on growth performance and feed utilization among 0-30% replacement of Ca(H2PO4)2 diets, but 40-50% replacement significantly went down(P<0.05). The ADCd and ADCpro of 30% replacement level was significantly lower than other diets(P<0.05).The ADCp of 20% replacement level was the highest, and 0-20% replacement level were significantly higher than 30%-50%(P<0.05).With higher acidic phytase replacement level, PRE was significantly decreased(P<0.05).With acidifier and different replacement level, there were no significant effects on the content of fish body protein and vertebrae phosphorus(P>0.05), but replacement level affected the content of fish body phosphorus and vertebrae ash very significantly(P<0.01). Acidifier significantly affected fish body composition but couldn't affect vertebrae composition. |
