| The dry matter degradibilities of4wheat samples of different origins were measured using a Simulated Digestion System (SDS-III) after adding different levels of xylananse. The In Vitro digestibilities wre compared with that of In Vivo ones, which were generated from male broilers following Fasting-Force Feeding procedure. The feasibility of the application of SDS-III system in evaluating the effects of xylanase in wheat-based diets were discussed according to the accordance of In Vitro and In Vivo results.Trail1The stability of bionic digestive system and its collaboratory study on the enzymatic hydrolyzate gross energy of duck-feedsThe dry matter digestibilities of18corn-soybean based duck diet samples, which were provided by Institute of Animal Science, the Chinese Academy of Agricultural Science (Beijing) for collaboratory studies, were determined in our laboratory according to the standardrised SDS operational procedure. The intra-and inter-batch variabilities were analysed according to the results obtained in our lab. The reproducibilities and precision of measurements were compared between our results and that of the Beijing parallel lab. The results showed that the maximum absolute difference of DMD measurements from the same instrument were not more than0.9%and1.3%for intra-batches and inter-batches, respectively, and that of variation coefficients for intra-bathes, inter-bathes, and total samples were not more than0.59%,0.57%, and0.59%, respectively. The variation coefficients of intra-bath, inter-bath were not more than0.66%,0.79%, and that of intra-laboratory, inter-aboratory, and total measurements were not more than0.84%,1.7%and1.9%, respectively. Fifiteen repeative measurements of each of2feed samples verified that99%of DMD varation could be controlled within0.6%and0.9%. In summary, the SDS-Ⅲ system was operating stablely in our laboratory.The results we got had a higher comparability with that of collab.Trial2Evaluation the dosage-response effects of xylananse in wheat using SDS-III system (in vitro)The wheat samples from4different origins were selected, and different levels of xylanase followed by0,500,2000,8000, and12500U/g were incorporated into the4cultivars, thus, forming20test samples. In addition, each sample was tested either withendogenous enzymes addition or not. The validated SDS-Ⅲ system was applied to evaluate the effects of xylanase levels, wheat origins as well as endogenous enzymes on the DMD of all tested samples. The results revealed that although endogenous enzymes significantly increased the digestibilities of the four wheat cultivars (P<0.01), the trends of DMD varations were similar to that of no endogenous enzymes addition counterparts. The regression coefficients of DMD between the paired treatments of the four wheat cultivars were0.751,0.758,0.789and0.679, respectively (P<0.01). The DMD of the four wheat cultivars all showed an increasing-then-decreasiing pattern as the elevation of xylanase activities. However, the DMD measurements differed significantly between the minimum and the maximum in each of the four cultivars (P<0.05). But the most effective dosage of added xylanase on DMD in the four cultivars were not thesame (P<0.05). In summary, there was a non-linear association between DMD of wheats and the levels of xylanase added, and there was an optimal level of xylanase that could achieve the best DMD in each wheat. According to the dose-response pattern, once the xylanase exceeded the optimal level, the xylanase would have a negetive effect on DMD. Hence, we proposed the effect as "negetive response-to-high levels of xylanase". Meanwhile, the DMD measurements also affected by the cultivars of wheat. The results indicated that endogenous enzymes might not required for the evaluation of the effects of xylanase on DMD of wheats using SDS-III system.Trial3The effects of xylanaseon digestibilities of wheat-based diets using Fasting-Force Feeding male broilers (in vivo)The effects of xylanase levels on apparent metabolic rate of wheat were evaluated in broiler chicken using the fasting-force feeding method. Moreover, the so-called ’negetive response-to-high levels of xylanase’ found in thein vitro expriment conducted in trial2 were further evaluated in this in vivo trial. The compostion changes of wheats using the SDS-Ⅲ system and the animal model were examined extensively to elucidate the potential reasons for this observed response. The results from the in vivo experiment could also be used to verify the efficiency of SDS-III for the evaluation of the effects of enzymes on the digesitibilities of feedstuffs in vitro. Forty-eight healthy adult male yellow-feathered broilers with an average body weight of2.5±0.2kg, aged over18weeks were selectedand alloted randomly to a2×3factorial design with three wheat cultivars (i.e., wheat No.1,2and4) and three levels of xylanase (i.e.,0,2000and12500U/g). This experiment was run in twice, and there were eight and ten replicates in each treatment in the first and second run, respectively. In each treatment, there was one broiler. Both of the two runs were conducted following the standarised fasting-force feeding procedure, and the feces samples were collected from all the individuals. Apart from the significant effect of xylanase on the digestibilities of crude ash (P<0.05), there was no effect observed on the rest examined nutrients. There was a significant positive association between the digestibilities of dry matter and protein obtained from thein vitro and in vivo studies. In contrast, a negative association was observed on crude ash and non-starch polysaccharides (P<0.01). Protein and dry matter are the major componets in wheat in both in vitro and in vivo studies. The results suggested the metabolic pattern of wheat obtained by SDS-III system and animal model was similar, and the variations between the two methods may attribute to the NSP contents in wheat and the increased protein content in broilers from the endogenous origin. The large variations of the results obtained from thein vivo study may also attenuate the dose-response of xylanase in the digestibilities of wheat. In conclusion, the SDS-III system could be a useful tool to predict the digestibilites of the main componets in diets. However, the accuracy of the results could also be interfered by NSP and crude ash in the diets. |
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