Acetohydroxamic Acid Synthesis And Its Effects On Rumen Urea Nitrogen Metabolism And Microbiota Of Dairy Cows

Urease inhibitor could reduce the hydrolysis rate of urea in the rumen of dairy cows,by inhibiting bacterial urease activity,which will benefit the utilization of urea in the rumen.The objectives of this study were to optimize acetohydroxamic acid(AHA)synthesis,then to evaluate the effects of the product(AHA)on urea nitrogen metabolism in the rumen of dairy cows using animal feeding experiment,and to evaluate the effects of AHA on rumianl microbiota.Results showed that the productive rate of AHA was 84.6%and the purity of AHA was 98%,after the optimization of reaction system and program.AHA significantly inhibited NH3-N and Urea-N concentrations in the rumen of dairy cows(P<0.01),but increased purine derivatives concentration in the urine(P = 0.01).There were no significant effects on blood NH3-N concentration,pH,routine blood indexes,milk yield,and milk fat and protein.Urea and AHA supplementation significantly increased the bacterial community diversity level according to the Shannon-Weiner index of 16S DGGE images.Urea supplementation reduced the abundance of cellulolytic bacteria,such as Ruminococcus albus,Ruminococcus flavefaciens,Fibrobacter succinogenes and Butyrivibrio fibrosolvens,but inhibition of urea hydrolysis by AHA addition alleviated the reductions during the early period of incubation.In addition,urea supplementation increased(P<0.01)the abundances of Pseudomonas,Streptococcus,Haemophilus,Neisseria and Actinomyces,but AHA addition decreased(P<0.01)them.It was concluded that synthesis of AHA was optimized.The product of AHA was benefit to ruminal urea nitrogen metabolim of dairy cows.Product of AHA slowed down urea hydrolysis rate,which increased ruminal bacterial diversity level and lessened the inhibition of cellulolytic bacteria growth.The rumen ureolytic bacteria were abundant in the genera of Pseudomoas,Streptococcus,Haemophilus,Neisseria and Actinomyces.