Study On The Effect Of Phytase On Availability Of Phytate Phosphorus In Plant Feed

Two experiments were conducted to investigate the effect of phytase on rapeseedmeal and cottonseed meal availability.The two-step in vitro method of pepsase-trypase wasperformed in experiment one to test the effect of phytase on rapeseed meal and cottonseedmeal. The results showed that: exogenous phytase could markedly improve the phosphorusdialysance of rapeseed meal and cottonseed meal (P＜0.01), and the phosphorus dialysancesignificantly depend on the added dosage of phytase (P＜0.01).Though, when the phytasewas more than 750U/kg, it's ability on releasing phosphorus of phytate phosphorus infeedstuffs decreased.Balance test and 3×3 Latin Square design were used in experiment two to investigatethe effect of phytase on rapeseed meal and cottonseed meal availability. TwelveDLY(Duroc×Landrance×Yorkshire) crossbred barrows were selected, and the initialaverage weight of the pigs was 42±5kg. Four groups were included in the experiment, andthe first one was control, which was fed corn-soybean meal base diet, and 250, 500,1000U/kg of phytase was added on the basis of the control,respectively, to constitute thesecond, third and the forth group. Two diets were formulated in which the rapeseed mealand cottonseed meal provided 20.1% phytate phosphorus of all phytate phosphorus. Eachturn of experiment lasted 8 days (6 days of preliminary experiment, and 2 days of formalexperiment), during the latter 2 days of formal experiment, manure and urine werecollected completely, and their content of total phosphorus and phytate phosphorus wereexamined. The results showed that:1. The digestibility of rapeseed meal and cottonseed meal were greatly increased by phytase(P＜0.01). The digestibility of phytate phosphorus and the added dosage of phytasewas quadratically curvelinear related((P＜0.001), and when the phytase were 945 and873U/kg, the digestibility of phtate phosphorus were 86.27% and 83.35%, respectively,which were the best of it. The digestibility of phytate phosphorus and total phosphorus'apparent digestibility was extremely linearly related (P＜0.001).2. The total phosphorus digestibility and retention ratio of rapeseed meal andcottonseed meal increased while the added dosage of phytase increased. The totalphosphorus apparent digestibility and retention ratio of rapeseed meal and cottonseed mealwas significantly improved when the phytase was 250U/kg, and the figure was 36.8% and27.7, 23.7 and 32.3%, respectively. When the phytase was 500U/kg, the total phosphorusapparent digestibility of rapeseed meal and cottonseed meal increased 56.5% and 45.2%(P＜0.05), and the total phosphorus retention ratio increased 64.2% and 53.0%,respectively. When the phytase was 1000U/kg, the digestibility increased 95.8% and88.8%(P＜0.01), the retention ratio increased 100.5% and 85.4%(P＜0.01).3. The phosphorus excretion of rapeseed meal and cottonseed meal was decreased bythe phytase. When the phytase was 1000U/kg, the decreased figure of excretion ofphosphorus in rapeseed meal and cottonseed meal were 28.5% and 24.4% (P＜0.05).In conclusion, phytase greatly improved the digestibility of rapeseed meal andcottonseed meal. Hence, the author recommend that the decent added dosage of phytase in rapeseedmeal and cottonseed meal be 945U/kg and 873U/kg, respectively. The total phosphorusdigestibility and retention ratio of rapeseed meal and cottonseed meal increased while thephytase increased, and the digestibility of phytate phosphorus and total phosphorus'apparent digestibility was extremely significant linearly related.