豆科和蓼科牧草的组合发酵特性研究

Study on in vitro fermentation characteristics of Leguminous grass mixed with Polygonaceous grass

应用体外发酵产气技术,评价了鲁梅克斯、三叶草和苜蓿分别以0∶100、25∶75、50∶50、75∶25和100∶0进行两两组合时的发酵特性。结果表明,鲁梅克斯与苜蓿组合时,不同组合比例间的发酵动力学参数差异不显著(P>0.05);苜蓿与三叶草组合时,理论最大产气量(A)及产气速率常数(b)以苜蓿占25%时最高,显著(P<0.05)高于苜蓿占75%的组合;鲁梅克斯与三叶草组合时理论最大产气量及产气速率常数分别以鲁梅克斯占25%和50%的组合最高,并显著高于鲁梅克斯占75%的组合。相同牧草组合时不同组合比例产气延滞时间之间的差异不显著(P>0.05)。不同牧草组合时不同比例组合牧草各时间点的产气量表现出显著的正组合效应或正组合效应趋势,在发酵12和24 h时,产气量最易出现显著的正组合效应,不同牧草组合时产气量的组合效应量随发酵时间的延长而下降。理论最大产气量、产气速率常数及48 h产气量(GP)与OM、ADF、NDS含量及NDS/CP呈显著正相关关系,而与CP、NDF及HC的含量呈显著负相关关系。发酵延滞时间与OM(P<0.001)、ADF(P<0.001)含量及NDS/CP(P<0.01)呈显著负相关关系,而与CP(P<0.001)及HC(P<0.001)的含量呈显著正相关关系。结论认为,组合牧草体外发酵产气程度主要受非结构性碳水化合物与粗蛋白比例的影响。

An experiment was conducted to investigate in vitro gas production characteristics of mixed forages. The mixed forages investigated in this experiment were Rumex mixed with Medicago,Rumex mixed with Trifolium,and Trifolium mixed with Medicago,all mixtures replicated at proportions of 0 ： 100,25 ： 75,50 ： 50, 75 ： 25,and 100 ： 0. The significant differences amongst the different mixtures of forage species,and the coefficients between in vitro fermentation kinetic parameters and different chemical compositions were analyzed and discussed in this paper. Based on results it was shown that there were no significant differences between the kinetic parameters and the different proportion mixtures of Rumex and Medicago. The recorded values of A and b of the mixed forages were the highest when the proportion of Medicago was 25%, and were significantly higher （P〈0.05） than the mixed forage of Medicago with Trifolium at 75%. The highest values of the theoretical maximum gas production and the rate of gas production occurred for the mixture of Rumex with Trifolium at 25 % and 50% respectively. Significant differences in lag time among different forage proportions were not found for the same mixed pastures. Statistically significant positive interaction effects or positive interaction effect tendencies were observed when the three species of forage were mixed with each other, significant positive associative effects of cumulative gas production were produced after 12 and 24 h in vitro incubation, and the extent of associative effects decreased with an increase in incubation time. Correlation analysis showed that the theoretical maximum gas production,the rate of gas production and cumulative gas production at 48 h were positively related to the content of OM,ADF,NDS and the ratio of NDS to CP,and negatively related to the content of CP,HC and NDF. The lag times were positively related to the content of CP （P〈0. 001）,HC （P〈0. 001）, and negatively related to the content of OM （P〈0. 001）,ADF （P〈0. 001） and the ratio of NDS to CP （P〈 0.01）. It is therefore suggested that the extent of in vitro gas production was primarily affected by the ratio of nonstructural carbohydrates to crude protein.