Effects Of Thermostable Phytase On Phytate Phosphorus Degradation, Growth Performance And Mineral Utilization In Broilers

Four experiments were conducted to study the effects of thermostable phytase on phytate phosphorus (PP) degradation, growth performance, mineral utilization in broilers. In experiment 1, collecting corn, soybean meal and cottonseed meal from ten regions, three samples per region, used as test materials. Study the correlation of PP, total phosphorus (TP) and crude ash (CA) by measuring the content of PP, TP and CA in these materials. In experiment 2, phytase levels were 0.00, 0.25, 0.50, 0.75, 1.00 FTU/g soybean meal, and this experiment was conducted to study the effect of different levels of phytase on releasing PP, and at the same time, cellulose enzyme (20 U/g), pectinase (20 U/g), xylanase (20 U/g) and complex enzyme [cellulose enzyme (7 U/g); pectinase (7 U/g), xylanase (7 U/g)] based on phytase (0.50 FTU/g) were added to soybean meal, and the NSP enzyme was evaluated. In experiment 3 and 4, a total of 900 Arbor Acres (AA) broiler chickens were allotted to three treatments with three replicates. The control group without phytase was arranged with adequate active phorsphate (AP): 1 to 28-d-old (AP: 0.45%) and 29 to 48-d-old (AP: 0.42%); other groups were low AP diets (1 to 28-d-old: 0.30%; 29 to 48-d-old: 0.28%) and supplemented with 500 or 750 phytase FTU/kg of diet. Broilers were fed corn-soybean diets and carried out raising, metabolism, abatage experiments to study the effects of thermostable phytase on growth performance, bone development and mineral utilization in broilers.The results of experiment 1 showed that: the contents of PP in corn, soybean meal and cottonseed meal were 0.12%-0.18%, 0.17%-0.28%, 0.54%-0.79%; the content of PP in cottonseed meal was the highest, and was 4.25 and 2.96 times more than the amount in corn and soybean meal. There were nice linear correlation between the content of PP and TP in these ingredients (P<0.01), and the correlation between PP and CA were lower.To predict the content of PP according to TP: Corn: PP = 0.02142+ 0.55114 TP R=0.87235,n=10,(P <0.01) Soybean meal: PP = - 0.40600+0.91100 TP R=0.93400,n=10,(P <0.01) Cottonseed meal: PP = 0.12404+0.50405 TP R=0.89384,n=10,(P <0.01)The results of experiment 2 showed that: supplementation of 0.25, 0.50, 0.75, 1.00 FTU/g phytase can release P about 72.21%, 79.09%, 85.43% and 87.19%. The amount of inorganic P released from soybean meal was increased when the levels of phytase activity in the soybean meal increased from 0.00 to 1.00 FTU/g soybean meal. The regression model between phytase levels (x,FTU/g) and P release (y , mg/kg): y=1131.6130+1200.9998(1-e-4.046x) R=0.9973, P <0.05. Cellulose enzyme, pectinase, xylanase and complex enzyme, based on phytase (0.50 FTU/g) can increase PP degradation by 0.10 %, 0.87 %, 1.55 %, 1.64 %.The results of experiment 3 showed that: decrease the diets AP by 0.15% (1 to 28-d-old: 0.30%; 29 to 48-d-old: 0.28%) and supplement 500 and 750 FTU/kg themostable phytase can't influence daily feed intake, weight gain, feed efficiency, carcass and bone qualities, ALP activity, serum calcium and phosphate (P >0.05). The supplementation of 750 FTU/kg themostable recombinant phytase has better effect in tibia strength at the age of 28-d-old (P <0.05).The results of experiment 4 showed that: Compared to control group, broilers fed diets with phytase can increase retentions of Ca, P and Zn; meanwhile, increased levels of Cu, Zn, Mg and Mn in tibia bone at the age of 28 d and Zn and Mn at the age of 42 d (P < 0.05); Zn and Mg in plasma were increased significantly at the age of 42 d (P < 0.05); diets with phytase also profit to environmental protection and ecology for decreasing the excreta nitrogen by 5.56%-5.18%, phosphate by 10.60%-12.64%.These results indicate that: There were close relationship between PP and TP in corn, soybean and cottonseed meal, and the content of PP can be predicted by TP and CA; the amount of P released from soybean meal was increased when the levels of phytase increased, and there was better correlation by curve fitting; at the same time, cellulose enzyme, pectinase, xylanase and complex enzyme have effect on the P release by phytase; the thermostable phytase can withstand steam-pelleting temperatures (90℃), and added to low P diets not only keep the broilers growth performance, but also profit to metabolic rate of Ca and P, and improve Cu, Zn, Mn and Mg utilization; at last, the thermostable phytase also profit to environmental protection.