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

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.