不同蛋白和中性洗涤纤维水平对瘤胃发酵、消化和微生物蛋白合成的影响

以3头装有瘤胃瘘管的干奶牛作为瘤胃液供体,用体外培养法研究不同日粮蛋白和中性洗涤纤维(NDF)水平对瘤胃发酵、消化和微生物蛋白合成的影响。采用2×3双因子完全随机设计,粗蛋白水平14%、16%和18%,NDF水平为32%和36%。体外发酵后2、4、6、12、24 h取瘤胃液测定pH、NH3-N浓度和微生物蛋白含量,发酵结束后测定饲料中干物质(DM)、NDF和酸性洗涤纤维(ADF)消化率。结果表明:随着蛋白水平升高,瘤胃发酵pH有增加趋势(P=0.079),显著提高NDF和ADF消化率和细菌蛋白合成量(P<0.05),但不影响DM消化率和原虫蛋白的合成量(P>0.05);日粮中NDF水平显著影响瘤胃pH、NH3-N浓度和ADF消化率(P<0.05),但不影响DM和NDF消化率以及微生物蛋白的合成量(P>0.05)。本试验条件下,日粮中16%CP和32%NDF组可在一定程度上促进瘤胃发酵,提高纤维消化率以及微生物蛋白的合成量。

Effect of Different Dietary Levels of Protein and NDF on the Ruminal Fermentation, Digestibility and Microbial Protein Synthesis in vitro

T hree ruminally cannulated dry cows were used to provide rumen fluid to investigate the effect of different dietary levels of protein and NDF on the ruminal fermentation,digestibility and microbial protein synthesis in vitro.A 2 × 3 two factorial random design was adopted: CP level(14%,16%,18%) and NDF level(32% and 36%).Rumen fluid samples were collected at 2,4,6,12,24 h after incubation and then pH,NH3-N and microbial protein yield were determined.The digestibility of DM,NDF and ADF were measured after the fermentation.The results showed that with increasing CP level pH tended to increased(P=0.079) and significantly increased digestibility of NDF,ADF and ruminal bacterial protein yield(P<0.05),however,neither DM digestibility or ruminal protozoal protein were related to CP level(P >0.05).A high NDF level influenced the pH,NH3-N and ADF digestibility(P <0.05),whereas the DM,NDF digestibility and microbial protein synthesis were not affected(P >0.05).Therefore,based on this study,16% CP combined with 32% NDF could promote the rumen fermentation,enhance the fiber digestibility and microbial protein synthesis.