Study On Predicting The Metabolizable Energy Of Soybean Meal In Ducks With Enzymatic Method

The objective of this study was to establish a reasonable enzymatic method for measuring the true metabolizable energy (TME) value of soybean meal in ducks. Based on the two-stage in vitro system with"pepsin-artifical duck intestinal fluid"established by our laboratory, A three-stage in vitro assay procedure with"pepsin-artifical duck duodenum-artificial ducks jejunum fluid"was established in this study.In the fist part, the objective was to establish a reasonable method for measuring the metabolizable energy (ME) value of soybean meal in ducks by compared the direct method with difference method in ME determination. Eighty-four adult ducks were randomly selected and divided into seven treatments with each contained four replications of 12 ducks. Seven treatments were used for measuring the ME value of 7 diets with the soybean meal content of 7 levels ( 0%, 10%, 20%, 30%, 40%, 50%, and 100%, respectively). The results showed that the metabolizble energy value of soybean meal in ducks determined by direct method was lower than that by difference method, but the coefficient variation was higher. However, in the measuring the ME value of soybean meal, the experimental dietary soybean meal content should between 40% and 50% in the difference method.In the second part, the artifical duodenum fluid and artifical jejunum fluid were designed according to the digestive enzymes activities range of intestinal fluid under normal physiology and nutrition condition. The optimum hydrolyzation conditions for pepsin, artifical duodenum fluid and artifical jejunum fluid were studied. The results showed that, the optimum concentration of pepsin was 1418.26U/ml, and hydrolyzation time was 3 h. The optimum hydrolyzation time for the artifical duodenum and jejunum fluid stage was 10 h, 10 h, respectively.The third part was conducted to predicting true metabolizable energy (TME) of soybean meal in ducks with enzymatic hydrolyzate gross energy (EHGE). The results showed there was no significant difference between EHGE and TME (P>0.05), which meant EHGE is equal to the value of true metabolizable energy of soybean meal. There was no fit model using EHGE or enzymatic method dry matter digestibility for improving the accuracy of the predicted TME of soybean mean in ducks.The fourth part conducted to compare the difference between chemical method and enzymatic method for predicting the true metabolizable energy of soybean meal in ducks. The results showed there were no significant correlations between NDF,ADF,CP,GE and TME content of soybean, which suggested the four chemical compositions could not be used for predicting the TME of soybean in ducks. Compared to the chemical method, the enzymatic method can predicted the TME of soybean with EHGE in ducks directly.