| The effect of microbial phytase (MP) and dark plum powder or citric acid supplementation in corn-soybean-rice bran based diet on hydrolysis of phytate phosphorus and digestibility of other nutrients were investigated in vitro assay and digestibility trial involving four DLY growing pigs, with average BW of 35±1.5kg, were fed four diets according to a 4×4 Latin Square design. The experimental diets were: 1) negative control (NC) formulated according to NRC (1998) except available P; 2) NC plus MP (500 U/kg); 3) NC＋MP and 1.5% dark plum powder; 4) NC＋MP and 1.5% citric acid. The experimental was divided into four periods which comprised 7d with a 3-d adaptation period and a 4-d collection of fecal samples. In vitro assay, the four diets were incubated under simulated gut conditions. Resu.lts indicated:1. In vitro assay, microbial phytase improved the hydrolysis of phytate phosphorus (31.73% Vs 81.95%, P＜0.01). The degradation rate of phytate phosphorus was further increased (P＜0.01) to 92.77% and 87.45%, respectively due to microbial phytase together with dark plum powder or citric acid,. The additive effect of dark plum powder on hydrolysis of phytate phosphorus by phytase was significantly stronger than artificial citric acid.2. In vivo assay, microbial phytase doubly improved apparent digestibility of phosphorus (36.58% Vs 76.26%, P＜0.01). Dark plum powder and citric acid further improved apparent digestibility of phytate phosphorus to above 89% and 82%, respectively. Equivalently avail phosphorus of the diet were improved by 0.19 and 0.17 percentage points, respectively, than diet without microbial phytase. An additive effect of dark plum powder and microbial phytase was found for digestibility of phytate phosphorus and effect of dark plum powder on improving the hydrolysis of phytate phosphorus by phytase was stronger than citric acid (8.67%, P＞0.05).3. Microbial phytase signigicantly improved the apparent digestibility of Ca (35.20% Vs 50.85%) and P (29.84% Vs 44.81%). When microbial phytase combined dark plum powder or citric acid, the apparent digestibility of calcium or phosphorus were significantly improved to above 64%, 59% and 61%, 50%(p＜0.01). An additive effect of dark plum powder and microbial phytase was found for utilization of Ca and P. equivalently, there was additional 0.07 percentage point digestible phosphorus released than phytase alone.4. There was no significantly effect of microbial phytase on CP utilization. Microbial phytase togther with dark plum powder or citric acid improved (P＜0.05) the apparent digestibility and retention of calcium or phosphorus to 4.14% or 14.02%, repectively.5. Microbial phytase improved the apparent digestibility of iron, copper, manganese or zinc(28.39%, P＜0.05 ). Phytase combined dark plum powder improved the apparent digestibility of iron and zinc to above 34% (P＜0.05), 65% (P＜0.01). Phytase combined citric acid improved the apparent digestibility of zinc to above 58% (P＜0.05), but not digestibility of iron (P＞0.05).6. Microbial phytase significantly (P＜0.01) decreased the content of phytate phosphorus, calcium, phosphorus and protein in manure. Dark plum powder further decreased (P＜0.05) the content of phytate phosphorus, calcium and phosphorus in manure, and citric acid only had the tendency of decreasing (P＞0.05) the content of phytate phosphorus, calcium and phosphorus in manure. The additive effect of the dark plum powder and phytase on decreasing the contents of phosphorus in manure was strong (P＞0.05) than that of artificial citric acid.7. Microbial phytase decreased the content of water solube phosphorus (WSP)in manure ( 0.60% Vs 0.47%, P＜0.05). Microbial togther with phytase dark plum powder decreased (P＜0.01) the content of WSP to 0.38%.In conclusion, microbial phytase significantly improved the hydrolysis of phytate phosphorus in diet. On the basis of phytase, dark plum powder and citric acid further improved the hydrolysis of phytatr phosphorus by microbial phytase, further enhanced the digestibition and utilization of Ca, P and other nutrients, further reduced environmental pollution, and An additive effect of dark plum powder and microbial phytase was found. Meanwhile, the additive effect of natural organic complexed acid, dark plum powder, on phytase was stronger than artificial citric acid.
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