| Seven studies were conducted in this dissertation to improve the digestive enzyme for simulating the hindgut digestion of swine in using simulative digestion system(SDS-ΙΙ), to establish an in vitro method for screening NSP enzymes of 4 swine diets, to investigate the NSP types on the endogenous AA flow and nutrient digestibility of corn- soybean and nitrogen-free diet. The effects of optimized NSP enzyme combinations on the digestibility of nutrients and degradation of NSP components were also conducted.Firstly, two experiments were conducted to provide data for improving the digestive enzyme for simulating the hindgut digestion of swine in using SDS-ΙΙ. In experiment 1, 24 pigs were used to investigate the effect of dietary fiber level on the ability of NSP enzymes in swine cecum. The pigs were allotted to 4 treatments and provided 4 different TDF level diet for 14 d(12.3, 14.6, 16.9 and 21.4% dietary fiber). 3 pigs of each treatment were slaughtered for measuring the ability of celluase, xylase, β-glucanase and pectinase in cecum. The results indicated that the TDF level had no significant effect on the ability of the 4 primarily NSP enzymes. In experiment 2, The NSP contents of corn, soybean meal, wheat bran, corn DDGS, alfalfa and soybean hull were measured. Following the simulated digestion in the stomach and small intestine of feedstuffs, 3 enzymes(cellulase, Viscozyme and bionic enzyme, which was prepared by the results of exp.1) were used to stimulate the hindgut digestion. Each treatment contained 5 replicates, the DMD, GED and EHGE of each treatment were determined. The results showed that the DMD of corn, soybean meal and soybean hull and the EHGE of soybean meal and soybean hull increased by the 3 digestive enzyme(P<0.01).The DMD and EHGE of alfalfa and DDGS were not affected by the inclusion of cellulase and the DMD and EHGE of wheat bran and DDGS were not affected by the inclusion of Viscozyme(P>0.05). Bionic enzyme improved the DMD of 6 feedstuffs and increased the EHGE of 6 feedstuffs with the exception of DDGS(P<0.01). The R-square of regression equation between the DMD, GED and NSP concentration using the bionic enzyme(0.95, 0.89) were higher than using the cellulase(0.94, 0.86) and using the Viscozyme(0.93, 0.81), respectively. The results from this study showed that using the bionic enzyme to simulate hindgut digestion based on the physiological value of pigs, has a significant effect on the in vitro digestion of feedstuffs than cellulase and Viscozyme. The bionic enzyme can be used to simulate the hindgut digestion using the SDS-ΙΙ.Secondly, the effects of digestive time of different phase on the in vitro digestibility of dry matter and energy of corn, soybean meal and wheat bran were investigated to establish an in vitro method for screening NSP enzymes of swine diet based on the physiological digestive enzymes of pigs and “flask+ shaking bath”. The results showed that the best digestive time of stomach and small intestine were 4 h and 22 h in the two-step in vitro method, and the best digestive time of stomach, small intestine and hindgut were 4 h,14 h and 24 h in the three-step in vitro method. The DMD and GED of 4 swine diets were determined using the in two-step and three-step in vitro method, and the results were compared with the in vivo value to evaluating the feasibility. The results showed that the coefficient of variation of the in vitro values were less than the coefficient of variation of the in vivo value, the correlation of DMD(R2 = 0.94) and GED(R2 = 1.00) of the 4 diets using the two-step in vitro and in vivo method was very high(P < 0.05), and the of DMD(R2 = 0.90) and GED(R2 = 0.94) of the 4 diets using the three-step in vitro was also had a good correlation with in vivo method(P < 0.05). The results from this study showed that the in vitro method based on the physiological digestive enzymes of pigs and “flask+ shaking bath” can evaluate the digestibility of swine diets accurately, and could be used for screening NSP enzymes of swine diet.Thirdly, the effects of NSP enzymes on the in vitro dry matter digestibility(IVDMD) of corn-soybean meal diet, corn-soybean meal-DDGS diet, corn-miscellaneous meal diet and wheat-soybean meal diet for growing pig were measured using the in vitro method established in the second part. Aim is to resolve the problem of massive work and poor comparability for screening NSP enzymes by animal experiment. The first step was to determine the dose-response of the NSP enzymes(cellulase, xylanase, β-glucanase, β-mannanase, α-galactosidase and pectinase) on the IVDMD of diets using one-way randomized experimental design. The second step was to screen the optimal combinations of the 6 NSP enzymes using quadratic regress-orthogonal rotary design. The results showed that the NSP enzymes had quadratic effects on the IVDMD of diets were observed, The IVDMD of the 4 diets were increased by 3.26%(corn-soybean meal diet), 3.89%(corn-soybean meal-DDGS diet), 3.75%(corn-miscellaneous meal diet) and 3.48%(wheat-soybean meal diet) respectively. The results from this study showed that the combination of the 6 NSP enzymes could improve the IVDMD of growing pig diets more effectively.Fourthly, the effects of NSP type on the apparent digestibility of nutrients in swine N-free diets and endogenous AA flow were investigated, in order to provide data for improving the N-free diet method in the measurement of standardized ileum digestibility(SID) of AA in feedstuffs. 15 ileal-cannulated pigs(initial BW=50.7±5.2 kg) were allotted to 5 treatments in an incomplete block design(5?2). The pigs were provided a corn starch N-free control diet or a diet in which corn starch was partly replaced by 5% inulin(INU), carboxymethylcellulose sodium(CMC), microcrystalline cellulose(MCC) or Solka floc(SF). The apparent ileal digestibility(AID), apparent total tract digestibility(ATTD) of nutrients and endogenous AA flow were measured. The results indicated that NSP type can affect the AID and ATTD of nutrients and energy in N-free diet, soluble CMC and inulin can reduce the AID of nutrients and energy more significantly than insoluble MCC and SF, inulin with high fermentability improved the hindgut fermentation of nutrients(P<0.05), while CMC, MCC and SF(with lower fermentability) reduced the ATTD of nutrients(P<0.05), especially viscous CMC. High viscous CMC improved the water content and viscosity of feces and the endogenous AA flow(P<0.01). The results from this study showed that CMC is not a good fiber source adding to the N-free diet compared with insoluble and lower fermentable MCC and SF.Fifthly, the effects of NSP type on intestinal nutrient and energy digestibility and hindgut fermentation of corn-soybean meal diet in growing pigs were investigated. 6 ileal-cannulated growing pigs were allotted to 3 treatments in a replicated 3?3 Latin square. The pigs were provided a corn-soybean meal control diet or a diet in which corn and soybean meal was partly replaced by 5% inulin(INU) or carboxymethylcellulose sodium(CMC). The AID, ATTD of nutrients and energy, AID and SID of AA were measured. The VFA concentration was also determined in the ileal and fecal samples. The results showed that the AID of DM, CHO, NDF and GE were less(P?0.01) for pigs fed the INU diet than those fed the control and CMC diets. The ATTD and hindgut fermentation of DM, CHO, ADF, NDF, and GE were less(P?0.01) in the CMC diet than in the control diet or the INU diet, whereas, the AID of CP was greater(P?0.05) in the CMC diet than in the other diets. The hindgut fermentation of CHO and GE were greater(P?0.01) in the INU diet than in the control diet or the CMC diet. The fecal acetate and total VFA concentrations were greater(P?0.01) in pigs fed the INU diet than fed the control diet or the CMC diet. The fecal pH and concentration VFA were less(P?0.01) in pigs fed the CMC diet than those fed the control diet or the INU diet. In conclusion, addition of 5% inulin into a diet had a low digestibility of nutrients and energy in upper gut and high hindgut fermentation. In contract, the CMC increased the AID of CP and reduced other nutrient and energy digestibility and fermentation.Sixthly, the effects of the NSP enzyme combinations optimized in the third part on intestinal nutrient and energy digestibility and hindgut fermentation in the 4 growing pig diets were investigated. 24 ileal-cannulated pigs(initial BW=50.9±4.9 kg) were allotted to 8 treatments in an incomplete block design(8?3). 8 diets(the 4 diets with or without the addition of the optimal NSP enzymes combination) were fed to the pigs. The results showed that the difference extent of AID were higher than the ATTD of the same nutrient in different type diets, the optimal NSP enzymes combination increased the AID of DM and NDF in corn-soybean meal diet(P?0.05), pigs fed the corn-miscellaneous meal diet with the addition of NSP enzymes had greater AID of all nutrients but EE(P?0.05) than those fed the diet without NSP enzymes. The optimal NSP enzymes combination decreased the AID of DM, GE, CP and ash in corn-soybean meal-DDGS diet(P?0.05), but increased the AID of NDF(P?0.01), pigs fed the wheat-soybean meal diet with the addition of optimal NSP enzymes combination also had lower AID of DM, GE, CP, CHO and ash(P?0.05), but increased the AID of NDF(P?0.04) compared with those fed the diet without NSP enzymes. The optimal NSP enzyme combinations were all increased the ATTD of nutrients in the 4 diets with different extent, only increased the ATTD of DM, GE, CP and EE in corn-miscellaneous meal diet and GE, CP and EE in wheat-soybean meal diet significantly(P?0.05).Finally, the effects of the optimal NSP enzymes combinations on the degradation of NSP components in the 4 growing pig diets were also investigated. The results showed that the AID of SNSP were higher than the INSP in all 4 diets with no NSP enzymes, the SNSP and its components were degraded almost completely. The optimal NSP enzymes combination increased the AID of the most components of INSP in corn-soybean meal diet(P?0.05), increased the ATTD of the most components of TNSP and total SNSP(P?0.05). Pigs fed the corn-miscellaneous meal diet with the addition of optimal NSP enzymes combination had greater AID and ATTD of the most components of INSP and total INSP(P?0.05) than those fed the diet without NSP enzymes, and the ATTD of the components of TNSP had a tendency(0.05?P?0.10) to increase in corn-miscellaneous meal diet with the addition of NSP enzymes. The optimal NSP enzymes combination increased the AID of INSP and its most components(P?0.05), but decreased the AID of SNSP and its most components in corn-soybean meal-DDGS diet(P?0.01), and increased the ATTD of xylose, arabinose and uronic acid of INSP(P?0.05). Pigs fed the wheat-soybean meal diet with the addition of optimal NSP enzymes combination had greater AID of galactose and uronic acid of TNSP(P?0.05) and ATTD of galactose, rhamnose and fucose of TNSP(P?0.05) than those fed the diet without NSP enzymes. The AID of total INSP content had a tendency(P = 0.09) to increase in wheat-soybean meal diet with the addition of NSP enzymes. The results from this experiment showed that the degradation of NSP components and the effects of NSP enzymes on the digestibility of nutrients were varies with the composition of the diets. |
PDF Full Text Request