| With the development of bio-technique and fermentation technique, feed enzyme product brands and production increased rapidly. So, it's very important to establish a valid and reliable method for enzyme evaluation. At present, there are two primary methods used in exogenous enzymes preparation evaluation. One is enzyme activities assay, animal experiment is another one, but both of them have some limitation. Therefore, it's necessary to found a simple, quick and economical method in lab for feed enzyme efficacy evaluation and selecting effective and economical enzyme products. The objects of this study were to establish a method imitating broiler digestion in vitro and test its feasibility and validity in evaluating feed enzyme efficacy, predicting animal performance and nutrients digestibility.Experiment 1. Development of digestive parameters in broiler with ageIn this experiment, digestive parameters development model with age, which can provide digestive parameters for digestion device in vitro to imitate nutrients digestion in broiler, and relationship between digestive parameters development and broiler growth were studied by determining digestive parameters, body weight and feed intake at different ages. 174 day-old AA male broilers were randomly assigned to 3 groups, which were provided corn-soybean meal diet and water for ad libitum. On 10,14,17, 21,28,35,42 and 49 days, 10,9,8,7,6,6,6 and 6 of chicks in each group were killed by cervical dislocation. Moisture, pH and digestive enzyme activities of chyme in crop, proventriculus and gizzard, duodenum, jejunum and ileum were measured. The small intestine length was determined too.Chyme pH in crop, proventriculus and gizzard increase gradually with age. The pH in jejunum and moisture of chyme in different part of digestive tract keep stable with age, but small intestine length increased greatly with age. Small intestine development deficiency will be a factor affecting broiler growth during young age period. Pepsin rises with age rapidly and reaches peak value on 28-day, then decrease slowly. Pepsin insufficient secretion before 28-day maybe limit broiler growth. Comparing to duodenum and ileum, digestive enzyme activities in jejunum content keep high level generally. Amylase and trypsin in jejunum increased fast with age and attained peak value about 35 and 21-day respectively. Chryomtrypsin and lipase in jejunum reached peak value at 14-days, and don't show any insufficiency in chryomtrypsin and lipase secretion during young age period. The ages of digestive enzyme peak value in jejunum are different between 4 expressing ways. When the enzyme activities expressed by U/mg protein amylase trypsin and chyomtrypsin peak value were putIVoff. 4 enzymes expressed by U/g chyme fresh weight, U/g chyme dry matter weight and U/m?AIA show same development tedency.Experiment 2. Establishing a digestion device in vitro to imitate digestion in broiler and its related parameters being studied.In this experiment, pH, moisture, digestive enzymes level and retention time of chyme in crop, proventriculus and gizzard, and small intestine were made certain respectively according to the results of digestive parameters developing model with age in chapter 1 and documents published. Several commercial digestive enzymes products from porcine pancreas, such as pepsin, pancreatin, trypsin, amylase and lipase, were used to imitate pancreas secretion nutrients digestive process in broiler gastric-intestinal tract. The continuous dialysis method was adopted to eliminate inhibition of digested product to digestive enzyme and simulate digested nutrients absorption in small intestine. Effects of buffer circulating rate, bile extract, Dialysis tube molecular weight cutoff, particle size and weight of feed sample on crude protein (CP) and starch digestibility in vitro were studied too.The digestibility of CP and starch rise with buffer circulation rate increase, and reach maximum values at the rate of 2.5ml/min. CP and starch digestibility were improved by addi...
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