紫花苜蓿与披碱草混合青贮对体外瘤胃发酵特征的影响

Effects of Mixed Silage of Elymus dahuricus and Medicago sativa on in Vitro Rumen Fermentation Characteristics

为探究不同比例的紫花苜蓿和披碱草的混合青贮效应对人工体外瘤胃发酵参数的影响,以紫花苜蓿单独青贮为对照,采用体外瘤胃发酵法对紫花苜蓿和披碱草按照不同比例进行混合青贮,分析6~24 h内青贮的体外产气量(GP)、甲烷产量(CH_(4))、氨态氮(NH_(3)-N)、体外干物质降解率(IVDMD)、pH、挥发性脂肪酸(TVFA)等体外消化参数,并通过计算多项指标综合指数(MFAEI)对各试验组进行综合评定。结果表明:各处理组的GP、CH_(4)、NH_(3)-N、IVDMD均随发酵时间而升高,pH在6.24~6.77之间且差异不显著(P>0.05)。混贮组的GP、CH_(4)、IVDMD、乙酸(AA)、TVFA和乙酸/丙酸(AA/PA)值在各时间段内均呈现A_(2)组>A_(3)组>A_(4)组的趋势,且显著高于A_(1)组(P<0.05);NH_(3)-N浓度随发酵时间呈A_(4)组>A_(3)组>A_(2)组的趋势且显著高于A_(1)组(P<0.05)。紫花苜蓿单贮(A_(1)组)时AA/PA<3,瘤胃内发酵类型属于丙酸发酵,随着混贮中披碱草含量的增加,AA/PA值在各时间段内显著增加(P<0.05),其中A_(2)组在6 h~24 h内AA/PA>3,瘤胃中发酵类型由丙酸发酵转变为乙酸发酵。根据瘤胃发酵的各项指标和多项指标综合指数后A_(2)组最高,30%紫花苜蓿+70%披碱草混合青贮的体外消化效果最佳。

In order to explore the influence of the mixed silage effect of different proportions of Medicago sativa and Elymus dahuricus on artificial in vitro rumen fermentation parameters,the in vitro rumen fermentation method was used on mix silage of Medicago sativa and Elymus dahuricus in different proportions,with alfalfa silage as the control,to study in vitro gas production(GP),methane production(CH_(4)),ammonia nitrogen(NH_(3)-N),in vitro dry matter degradation rate(IVDMD),pH,volatile fatty acid(TVFA)and other in vitro digestion parameters of silage within 6 h~24 h,then multiple index comprehensive index(MFAEI)was comprehensively evaluated in each test group.The results showed that the GP,CH_(4),NH_(3)-N,and IVDMD of each group increased with time.The pH value was between 6.24 and 6.77 and there was no significant difference(P>0.05).The GP,CH4,IVDMD,AA,TVFA and acetic acid/propionic acid(AA/PA)in mixed silage group showed a trend of A_(2)>A_(3)>A_(4) in each period,which were all significantly higher than group A_(1)(P<0.05).The concentration of NH_(3)-N showed a trend of A_(4)>A_(3)>A_(2) with fermentation time and was significantly higher than that of A_(1)(P<0.05).When Medicago sativa was made silage(group A_(1)),AA/PA<3,which illustrated the fermentation in the rumen was propionic acid fermentation.As the content of Elymus dahuricus in mixed silage increased,the AA/PA value increased significantly in each period(P<0.05).In group A_(2),the AA/PA>3 within 6 h~24 h,showing the type of fermentation in the rumen had evolved from propionic acid fermentation to acetic acid fermentation.According to the indexes of rumen fermentation and the comprehensive index of multiple indexes,group A_(2) got the highest mark,indicating that the mixed silage of 30% Medicago sativa+70% Elymus dahuricus has the best in vitro digestive effect.