北方主要粗饲料不同组合体外发酵效果的研究

Effect of different combinations of main roughage in northern China by in vitro fermentation

为研究北方主要玉米秸秆、羊草和玉米秸秆青贮不同组合比例体外发酵特性,筛选不同饲料组合应用的最适比例,将羊草和玉米秸秆组合按不同比例进行体外发酵试验,筛选出最佳组合比例,再与玉米秸秆青贮按不同比例进行组合,进一步筛选出粗饲料最优组合。试验利用体外发酵测定不同粗饲料组合产气量、干物质消失率(DML)、pH值、微生物蛋白(MCP)、氨态氮(NH_(3)-N)、挥发性脂肪酸(VFA),计算各组合的单项组合效应值和综合组合效应值。结果表明:1)羊草与玉米秸秆按不同比例组合后,产气量各组间均随发酵时间的延长而增加,同一时间点产气量随玉米秸秆比例的增加而减少;DML产量均随玉米秸秆比例的增加而呈现增加的趋势,0∶100比例组合极显著高于其余比例组合(P<0.01);各比例组合间pH值差异不显著(P>0.05);MCP产量均随玉米秸秆比例的增加而呈现减少的趋势,各组合间存在差异极显著(P<0.01);而NH_(3)-N浓度随玉米秸秆的比例的增加而增加;除丁酸外,其他VFA各组均随玉米秸秆添加量增加呈先上升后下降的趋势。2)羊草-玉米秸秆:玉米秸秆青贮组合后,产气量各组合间均随发酵时间的延长而增加,且在同一时间点的产气量是随玉米秸秆青贮比例的增加而降低;各比例组合间pH值无显著差异(P>0.05);DML、MCP和NH_(3)-N产量均随玉米秸秆青贮比例的增加而呈现减少的趋势,DML各组合间存在极显著差异(P<0.01),MCP和NH_(3)-N各组合间存在显著差异(P<0.05);乙酸、总挥发性脂肪酸的浓度各比例组合间存在极显著影响(P<0.01),丙酸在比例为100∶0和50∶50组合差异极显著(P<0.01),丁酸各比例组合差异不显著(P>0.05)。总之,以综合组合效应评定指数评定各组合效应,羊草:玉米秸秆组合为60∶40时产生最大正组合效应、羊草-玉米秸秆:玉米秸秆青贮组合为50∶50时产生最佳正组合效应。

In order to study the in vitro fermentation characteristics of corn stalk,Leymus chinensis and corn stalk silage in different proportions in northern China,and to determine the optimum proportions of different feed combinations of those roughage products,Leymus chinensis and corn stalks were used in combinations of different proportions and were fermented in vitro so as to select the best combination ratio.Then,Leymus chinensis and corn stalk silage were combined in different proportions to further determine the optimum combinations of the roughage.In vitro fermentation was used to measure the gas production,dry matter loss,pH,microbial crude protein,NH_(3)-N and volatile fatty acids of different roughage combinations;and the single-factor associative effects and multiple-factor associative effects of each combination were calculated.The results showed as follows:1)The gas production increased with the extension of fermentation time of the different proportion groups of Leymus chinensis and corn stalks,but decreased with the increase of the corn stalk ratio at the same time point.DML increased with the increase of the corn stalk ratio,and the combination ratio of 0∶100 was significantly higher than the other ratios(P<0.01).However,there was no significant difference in pH among the tested groups(P>0.05).MCP decreased with the increase in the corn stalk ratio,and there was a significant difference among the combinations(P<0.01).The concentration of NH_(3)-N increased with the increase in the proportion of corn stalks.Except butyric acid,the other volatile fatty acids in each group increased first and then decreased with the increase in corn stalk addition.2)For the Leymus chinensis-corn stalks:cornstalk silage combination,the gas production increased with the extended fermentation time among the groups,and the gas production at the same time point decreased with the increase in the proportion of cornstalks silage,but there was no significant difference in pH among the groups(P>0.05).The dry matter loss,microbial crude protein and NH_(3)-N concentrations decreased with the increase of corn stalks silage,the dry matter loss was significant(P<0.01),and there was a significant difference between the contents of microbial crude proteins and NH_(3)-N(P<0.05).The concentrations of acetic acid and total volatile fatty acids among the groups were very significant(P<0.01).Propionic acid concentrations at 100∶0 and 50∶50 combinations were significantly different(P<0.01);but the combination of butyric acid ratios was not significant(P>0.05).To sum up,the maximum positive combination effect of Leymus chinensis:corn stalk was the ratio of 60∶40;and that of Leymus chinensis-corn stalk:cornstalk silage combination was 50∶50.