| In this research,beef cattle were used as experimental animals to study the effects of tannic acid on rumen fermentation,rumen microbial flora,nitrogen utilization,nutrient digestibility and blood biochemical parameters,also the study on the rule of degradation of tannic acid in the rumen,to explore the mechanism on utilization of dietary nitrogen and nitrogen emissions in beef cattle with tannic acid addition.1.Effects of tannic acid on rumen fermentation,methane emission and rumen microbial floraFour adult Simmental male cattle(376 ± 9.0 kg initial BW),fitted with permanent rumen cannulas,were used in a 4 x 4 Latin square design to investigate the effects of dietary supplementing tannic acid on rumen fermentation,methane emission and rumen microbial flora.Four levels of TA,i.e.0,6.5,13.0,or 26.0 g/kg dry matter(DM),were added to the basal ration consisted of corn silage and concentrate mixture as experimental treatments.Each experimental period consisted of a 12 d adaptation phase followed by 3 d sampling phase.The results showed that addition of tannic acid did not affect rumen pH value of cattle(P>0.05);supplementing tannic acid at 13.0 or 26.0 g/kg DM decreased(?)the concentration of NH3-N(P<0.05),tended to decrease the total volatile fatty acid(VFA)concentration of rumen fluid(P = 0.066),decreased the ratio of acetate to propionate(P<0.05)and the molar proportion of valerate and isovalerate(P<0.05),and increased the molar proportion of propionate(P<0.05);supplementing TA at 6.5,13.0 or 26.0 g/kg DM significantly decreased the CH4 production expressed in L/d,L/kg dry matter intake,L/kg digested dry matter,L/kg digested organic matter,L/kg digested neutral detergent fiber(P<0.05);it was found that the addation of tannic acid to the ration can decrease the methane emission and change rumen fermentation parameters.Real-Time PCR technique was conducted to monitor the microbial populations in the rumen including protozoa,methanogens,fungi,Ruminococcus albus,Fibrobacter succinogenes,Ruminococcus flavefaciens,Butyrivibrio fibrisolvens,Selenomonas ruminantium,Ruminobacter amylophilus,Streptococcus bovis.The results showed that supplementing TA at 26.0 g/kg DM decreased the relative abundance of protozoa,methanogens and Ruminococcus albus(P<0.05);supplementing TA up to 26.0 g/kg DM did not affect the relative abundance of fungi,Fibrobacter succinogenes,Ruminococcus flavefaciens,Butyrivibrio fibrisolvens,Selenomonas ruminantium,Ruminobacter amylophilus,Streptococcus bovis(P>0.05).2.Effects of tannic acid on nutrient digestibility,nitrogen utilization and blood biochemical parametersFour adult Simmental male cattle(376 ± 9.0 kg initial BW),fitted with permanent rumen cannulas,were used in a 4 x 4 Latin square design to investigate the effects of dietary supplementing tannic acid on nutrient digestibility,nitrogen utilization and blood biochemical parameters.Four levels of TA,i.e.0,6.5,13.0,or 26.0 g/kg dry matter(DM),were added to the basal ration consisted of corn silage and concentrate mixture as experimental treatments.Each experimental period consisted of a 12 d adaptation phase followed by 3 d sampling phase.The results showed that supplementing TA at 26.0 g/kg DM decreased the DM and OM digestibility(P<0.05),and at 6.5,13.0 or 26.0 g/kg DM decreased the CP digestibility(P<0.01)whereas did not affect EE,NDF and ADF digestibility(P>0.05);supplementing TA increased the ratio of faecal N/total N excretion and decreased that of urinary N/total N excretion(P<0.05)while the total N excretion and N retention was not affected(P>0.05);supplementing TA increased the urinary hippuric acid excretion and allantoin excretion(P<0.05),and decreased the urinary urea excretion(P<0.05).Consequently supplementing TA increased the rumen microbial N flow predicted based on total urinary PD(P<0.05);supplementing TA increased plasma concentration of T-AOC and decreased the plasma urea nitrogen concentration(P<0.05),whereas did not affect the plasma concentration of Glu,TC,TG,TP,Alb,AST,ALT,GSH-Px and SOD(P>0.05).The excretion of hippuric acid in urine and the amount of TA added in the ration had a positive correlation,the regression equations:Y = 0.008 X + 17.116(R2 = 0.501,n = 16,P = 0.002).The amount of TA added in the ration and the excretion of resorcinol and pyrogallol in urine had a positive quadratic correlation,the regression equations:Y = 0.124 + 0.034 X-0.0001 X2(R2 = 0.741,n = 16,P<0.001);Y = 0.020 + 0.011 X-0.0001 X2(R2 = 0.715,n = 16,P<0.001).3.The degradation of tannic acid in the rumen and excretion in urineFour Simmental male cattle with initial liveweight of 503 ± 15 kg and fitted with permanent rumen cannulas,were conducted into three periods by self-control design.The basal ration was consisted of corn silage and concentrate mixture.Total mixed rations(TMR)were used as a basal diet in control period.Cattle were fed with tannic acid 10.0 or 20.0 g/kg DM to the TMR in experiment period.Each experimental period lasted 17 days,of which the first 12 days were for pre-treatment and the last 5 days were for sampling.The rumen fluid samples were collected for six time point(after morning feeding 2 h,4 h,6 h,8 h,12 h and 24 h).The total urine was collected five days.The results showed that gallic acid,resorcinol and pyrogallol were not detected in the control phase.The concentration of pyrogallol,gallic acid and resorcinol in rumen fluid were in the range of 303.67 ± 21.50-428.70 ± 22.03 μg/mL and 345.55 ± 27.74-525.71 ± 50.62 pg/mL,1.79 ± 0.41-4.77 ± 0.18 pg/mL and 2.52 ± 1.32-6.29 ± 0.49μg/mL,3.71 ± 0.97-14.38 ± 2.18 pg/mL and 4.82±1.18-16.36 ± 4.93 pg/mL,respectively.The average output of pyrogallol and resorcinol in urine for 5 days with tannic acid 20 g/kg DM in the ration was significantly higher than supplementation tannic acid 10 g/kg DM in the ration.In summary,supplementing tannic acid at 26.0 g/kg DM decreased the ratio of acetate to propionate and CH4 production,decreased the relative abundance of protozoa,methanogens and ruminococcus albus,and decreased DM,OM and CP digestibility.Supplementing tannic acid at 13.0 g/kg DM increased the faecal N/excretion and decreased urinary N excretion while the N retention was not affected(P>0.05),and increased the urinary hippuric acid.The average output of pyrogallol and resorcinol in urine for 5 days with tannic acid 20 g/kg DM in the ration was significantly higher than supplementation tannic acid 10 g/kg DM in the ration(P<0.05). |
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