A Study On The Optimum Sites Of Phytase In Broiler Gastrointestinal Tract

Microbial phytase can raise the utilization of plant feed phytate phosphorus, and lower the addition of inorganic phosphate in the feed. Phytase can ease phosphorus shortages and environmental pollution caused by phosphorus. However, the potential for practical application of phytase has not been brought into full play. This is mainly because it is lack of a scientific theoretical guidance in the area of efficient application of phytase. At present the application of phytase in broiler diets, is mainly concentrated on phytase increase the nutrition of feedstuff and the performance of broilers. The appropriate sites of phytase in broiler gastrointestinal tract and the model it released has not been reported. This study using broilers as experimental animals, as the changes of activity (phytase), substrate (phytate) and product (Pi) in the broiler intestinal tract, reveal the appropriate sites of phytase in broiler gastrointestinal tract. The study will provide theoretical guidance for the efficient applications of phytase, like development of new phytase, phytase release at specifically gastrointestinal sites in broilers, and application of coating technologies.1. A Study on the mechanism and suitable sites ofphytase in broiler gastrointestinal tractThe first part of the study was carried out in vitro conditions, it analyzed the phytase activity under the parameters of broiler gastrointestinal tract, and simulated the loss of phytase activity in gastric and intestinal of broilers with day; Secondly, through feeding test measured the phytase activity in the gastrointestinal thyme, and found the main factor affecting phytase activity and the main survival sites of the phytase. The results show that: in vitro conditions, phytase activity has two peaks at pH 3 and 5.5; the closer to pH 3.0 and 5.5 the higher at phytase relative activity; at pH2.5-7.5, the phytase activity can be maintained above 30%, and when the pH was higher than 6.0, the activity was dropped quickly; at 41℃, phytase through different pH buffer handling, it's activity is stabilization after it decreased promptly for 30 minutes; the destruction of phytase in small intestine more than in stomach; phytase through the stomach into the small intestine in different days broilers, phytase activity be recovered slightly only occurred in the 14-day-old broiler group, and into the optimum pH 5.5, the resumption of the phytase activity has been found in all three day-groups, in descending order of 28,42 and 14 days; phytase has been seriously damaged in small intestine, remaining 20% of activity, and the three day-groups? are not very different. In vivo conditions, crop, stomach, duodenum, distal-jejunum cutting, proximal-jejunum and ileum had 55%～57%, 3%～9%, 28%～29%, 10%～11%, 3%～5% and 1%～2% phytase activity reservations, and showed a decreasing trend with age increased, phytase activity retention rate showed no significant difference in crop and duodenal of broiler with age (P＞0.05). Phytase activity retention rate are not difference between 14 and 28-day In distal-jejunum (P＞0.05), significantly higher than 42-day (P＜0.05). In proximal-jejunum, there are not much difference between 14 and 28-day (P＜0.05), 55% higher than 42-day (P＜0.01).2. A study on the rule ofphytate release in broiler gastrointestinal In this study has found the site being rich with the soluble substrates, by measuring dissolved rate of phytate in broilers' digestive tract with age,and find the rich site of phytate that suit phytase function in whole digestive tract. The results show that: In addition to the stomach and ileum, dissolution rate of phytate in thyme increases gradually with moving to the end of digestive tract. Dissolution ratio of phytate is low in the three days broilers' stomach, about 3%. As in 14 and 28-day broilers, after entering into the ileum, dissolution ratio of phytate increases further, and for 42 days, the dissolution ratio decreases by 16%. Being attached to the dissolution ratio of phytate in crop, it is not much difference between 14-day and 28-day (P＜0.05), while for 42-day' broilers, it is significantly higher than the 14-day and 28-day (P＜0.01). Phytate dissolution ratio in duodenum of 14-day is 17% higher than 28-day (P＜0.01), while it is no significant difference with 42-day (P＞0.05). In proximal-jejunum and distal-jejunum, there is no significant difference between 14 and 42-day(P＞0.05), significantly higher than 28-day(P＜0.01).3. A study on the main site of inorganic phosphorus absorption in digestive tract of BroilerIn this study has determined the intestinal phosphorus main absorption site, by testing phosphorus retention of gastrointestinal chyme in broilers with different day. The results show that: the phosphorus absorption is mainly in duodenum and distal-jejunum. In this site, digestibility of phosphorus is about 68% of the total digestibility. Proximal-jejunum has also phosphorus absorption, accounting for 30% of total digestibility. Ileal absorption of phosphorus is little. In duodenum and distal-jejunum, comparing phosphorus digestibility, 14-day is 12% higher than 28-day and 42-day (P＜0.01), 28-day has little difference with 42-day (P＞0.05). In proximal-jejunal and ileal, digestibility of phosphorus has no significant difference (P＞0.05).