Effects Of Rumen Protected Folic Acid Supplementation On Ruminal Fermentation,Digestibility And Metabolism Of Beef Cattles Based On Different Protein Levels Diets

In order to evaluate the effects of rumen protected folic acid supplementation on growth performance,ruminal fermentation,digestibility and metabolism and blood indexes of beef cattles based on different protein levels diets,four Blonde D’Aquitaine steers with permanent ruminal cannula feeded standard protein diet or high protein diet(at the protein levels were 11.91%and 13.07%,respectively)supplemented with 0,0.07,0.14,0.21 mg/kg body weight per day rumen protected folic acid(RPFA)were used in two 4x4 Latin square designs.The results showed that dry matter intake in high protein diet significantly increased compared with standard protein diet(P<0.01).Rumen pH and molar ratio of acetate were lower(P<0.01)and total volatile fatty acids,NH3-N and molar ratio of butyrate were higher significantly in high protein diet than those of standard protein diet(P<0.01).High protein diet could highly significantly improve the ruminal effective degradability of DM in mixed concentrate and corn straw and OM in mixed concentrate(P<0.01),the ruminal effective degradability of NDF in corn straw was increased(P<0.05).The flora of rumen Ruminobacter amylophilus and Prevotella ruminicola,the enzyme activity of rumen pectinase,a-amylase,xylanase were extremely significantly higher in group of high protein diet than standard protein diet(P<0.01),the enzyme activity of rumen protease was higher(P<0.05).Digestibilities of DM and CP,intake nitrogen,digestible nitrogen,retention nitrogen,retention nitrogen and digestible nitrogen ratio increased highly significantly in high protein diet(P<0.01),digestibilities of EE and NDF were raised(P<0.05).Albumin,total protein and growth hormone of serum in high protein diet were very significantly higher than standard protein diet(P<0.01),while serum urea nitrogen decreased extremely significantly(P<0.01).Average daily gain in MRPFA group was significantly higher than Control group(P<0.01),feed conversion rate was significantly lower than Control group(P<0.01).Rumen pH,total volatile fatty acids and NH3-N were not affected by RPFA(P>0.05).Molar ratio of acetate in group of MRPFA increased than Control group(P<0.05),whereas propionate molar ratio decreased significantly(P<0.01).Ruminal effective degradability of nutrient in mixed concentrate gradually increased with the supplementation of RPFA,and the ruminal effective degradability of DM in corn straw was extremely significantly higher in MRPFA group than Control group(P<0.01),the ruminal effective degradability of NDF was higher than the group of Control(P<0.05).The flora of rumen Ruminobacter amylophilus and Butyrivibrio fibrisolvens,the enzyme activity of rumen a-amylase and cellulolytic enzymes in MRPFA group were extremely significantly higher than Control group(P<0.01).Digestibility of diet nutrient,digestible nitrogen,retention nitrogen,retention nitrogen and digestible nitrogen ratio increased with the increasing dose of RPFA compared with Control group.The concentration of total protein,growth hormone,methionine synthase,5,10-methylenetetrahydrofolate reductase and folic acid of serum in MRPFA group were extremely significantly higher compared with Control group(P<0.01),the concentration of homocysteine decreased highly significantly(P<0.01).The interaction of diets and RPFA had no significant effects on all indexs measured in this experiment(P>0.05).These results indicate that supplementation of RPFA in diet and high protein diet can increase the growth performance,improve the rumen environment,increase the digestibilities and ruminal degradability of nutrients and the concentration of albumin,total protein,growth hormone and folic acid in serum,decrease the concentration of serum urea nitrogen and homocysteine.The optimum dose of RPFA in this experiment is 0.14 mg/kg body weight per day.