瘤胃乙酸与丙酸摩尔比例的改变对瘤胃发酵及血液指标的影响

Effect of Changing the Molar Ratio of Acetate to Propionate in Rumen Fluid on Rumen Fermentation and Some Blood Indexes

通过向瘤胃灌注乙酸 :丙酸 :丁酸的摩尔比例分别为 75∶1 5∶1 0 ,65∶2 5∶1 0 ,55∶35∶1 0和 45∶45∶1 0溶液 ,并在连续灌注的作用下 ,以期达到最终改变瘤胃液中乙酸∶丙酸∶丁酸摩尔比例的目的。研究表明 :(1 )随着灌注液中丙酸浓度的提高 ,最终瘤胃液中丙酸的比例增加 ,乙酸的比例逐渐下降 ,与对照组差异显著 (P <0 0 5) ,丁酸的摩尔比例无论与对照组 ,还是各处理间均无差异 ;(2 )向瘤胃灌注的VFA溶液提供高于维持能量水平 30 %以上的能量 ,使瘤胃中总的VFA浓度、VFA产生速率、丙酸的产生速率及VFA的总产量均显著增加 (P <0 0 1 ) ;但是对基础混合日粮的干物质 (DM)、有机物 (OM)、中洗纤维 (NDF)、酸洗纤维 (ADF)、半纤维素 (HCF)等养分的消化率不构成显著影响 ;(3)当灌注溶液中丙酸所占摩尔比例增加到 35 % ,粪氮和尿氮的排出量显著减少 (P <0 0 5) ,从而提高日粮氮的沉积能力。进一步研究表明 ,当灌注液中丙酸的摩尔比例进一步提高至 45 %时 ,血糖浓度及胰岛素的浓度才显著增加 (P <0 0 5) ;但胰岛素与胰高血糖素的比值对于不同的处理或对照组 。

The four designed VFA infusions with different molar ratio of acetate:propionate:butyrate were used to establish final molar ratio of VFAs in the rumen of the sheep.It was found that the proportion of propionate in the rumen fluid at steady state increased with the increase of propionate in the mixture of VFAs,and the concentration of acetate was down gradually and different from un infused control group( P <0 05).The concentration of butyrate in the rumen fluid changed a little.The infused level of VFA was the equivalent of an additional 30% of ME requirement at maintenance and the study demonstrated that:①there were no differences in rumen pH,the digestibilities of DM,OM,NDF,ADF and HCF for mixed diet as well as the blood CO 2 combining power between different infused levels of VFAs.②The outputs of feces nitrogen and urine nitrogen reduced significantly( P <0 05)when the molar proportion of propionate in the rumen fluid was elevated to 23 95%,which indicated increasing the concentration of propionate in the rumen was helpful to deposit of dietary nitrogen by animal.Therefore,keeping a proper ratio of acetate:propionate in the rumen fluid is very important,especially for feeding high level of lower quality of roughages to both steers and sheep in our country nowadays.Meanwhile,when the molar proportion of propionate in the rumen fluid was elevated to 45%,the concentrations of both blood glucose and insulin elevated to 45%,the concentrations of blood glucose and insulin were increased significantly ( P <0 05),and both of them had a positive linear relationship with the increase of production rate of propionate in the rumen.When the ratio of insulin to glucagon was observed,it showed this ratio appeared constant in different groups,even for control group.