体外法研究纤维日粮的发酵特性及对猪氮排放相关指标的影响

摘要

[Objective]The present study was conducted to investigate and compare the fermentation characteristics and effects on nitrogen excretion related indicators of different fiber diets using anin vitro method in pigs. The study aimed to provide an experimental basis for the rational application of dietary fiber in pig production and for the preparation of diets to reduce nitrogen excretion.[Method]Wheat fiber (WF), wheat bran fiber (WBF) and oat bran fiber (OBF) were purified from wheat, wheat bran and oat bran, respectively, using the enzyme-gravimetric method (AOAC Method 985.29). WF diet, WBF diet and OBF diet based on maize and soybean were formulated to contain 5% WF, WBF and OBF. The three fiber diets were undergone a stomach-small intestine digestion of pigs by simulative digestion system (SDS-II). A total of six growing pigs, which were in good health and had similar weight, were used to collect fresh feces. The mixed feces and culture solution were compounded in an appropriate proportion to prepare inocula which were quantitatively charged into fermentation flasks for simulating large intestine fermentation. After the stomach-small intestine digestion, the digestive products were pooled. 200 mg digestive products were added into a fermentation flask filled with 30 mL of inocula, placed in an incubator at (39±0.25)℃. The fermentation were stopped at 4, 12, 24, 36, 48 and 72 h of incubation. Then the fermentation residues and fermentation broth were collected, and the relevant indicators were determined.[Result]The results indicated that in the large intestine fermentation stage, there were significant differences in dry matter degradability during thein vitro fermentation (IVDMD) and total short-chain fatty acid (SCFA) concentration, pH, ammonia nitrogen (NH3-N) concentration and microbial protein (MCP) production in fermentation broth among the three fiber groups (P0.05). At 4 h, the IVDMD of OBF group was 18.32% and 15.21% higher than WF group and WBF group, respectively (P0.05).在4 h,OBF组的IVDMD比WF组与WBF组分别高18.32%、15.21%(P<0.01);在12 h,比WF组与WBF组分别高14.87%、10.06%(P<0.01).(2)在发酵24与36 h,OBF组发酵液总SCFA含量显著高于其他两组(P<0.05),在72 h,OBF组与WBF组极显著高于WF组(P<0.01),在4与12 h,OBF组有高于其他两组的趋势(P=0.0599;P=0.0504).在24 h,OBF组发酵液总SCFA含量比WF组与WBF组分别高27.32%、17.11%(P<0.05);在36 h,比WF组与WBF组分别高16.65%、25.96%(P<0.05).(3)在发酵4与12 h,OBF组发酵液pH在3组中最低(P<0.01);在24、36与72 h,OBF组与WBF组显著低于WF组(P<0.05).(4)在发酵24与48 h,OBF组发酵液NH3-N浓度显著低于其他两组(P<0.05),并在12 h,有低于其他两组的趋势(P=0.0559).在24 h,OBF组发酵液NH3-N浓度比WF组与WBF组分别低6.86%、4.59%(P<0.05);在48 h,比WF组与WBF组分别低8.44%、7.09%(P<0.05).(5)在发酵4 h,OBF组发酵液MCP产量显著高于其他两组(P<0.05),并分别在12、24 h与36、48 h,显著高于WF组与WBF组(P<0.05).在4 h,OBF组发酵液MCP产量比WF组与WBF组分别高69.85%、82.25%(P<0.05).[结论]体外条件下,燕麦麸纤维显著提高了日粮在发酵阶段的干物质降解率、发酵液总短链脂肪酸含量与微生物蛋白产量,并显著降低了发酵液pH与氨氮浓度.因此,相比小麦纤维与麦麸纤维,燕麦麸纤维在促进微生物发酵及氮减排方面具有更高的潜力.