Effects Of Hydrogen On Ruminal Fermentation,Digestion,Metabolism And Methane Emission In Holstein Cows

Methane is the second largest greenhouse gas after carbon dioxide,Due to it can not be used by the host and rumen microbial and be released into the environment,leading to a greenhouse effect and also causing the energy loss.Methane is produced by the production of methanogenic bacteria using carbon dioxide and hydrogen in the rumen,so hydrogen is an important precursor of methane production.At present,reducing the generation of methane by reducing the generation of hydrogen has become the focus of research.But there is limited knowledge about the relationship between hydrogen and methane in the rumen.Therefore,the aim of this study was to investigate the effects of hydrogen on the rumen digestibility and the ruminal fermentation mode by adding magnesium to the basal diet,and provide a direct prove for the relationship between hydrogen and methane.The study is divided into the following two parts:1.Effects of hydrogen on rumen fermentation,digestion and metabolism and methane emissions from dairy cowThe aim of this study was to investigate the effect of hydrogen on the rumen fermentation,digestion and metabolism and methane emissions by adding magnesium to the basal diet.Four weaned Holstein cattles?2-3 fetuses,BW:480-580 kg?were randomly allocated to the experimental group and control group using the cross-test method.Mg and Mg?OH?₂ were added to the basal diet at the dose of 0.6%DM.The test period was lasted for41 days,after 5 days of pre-feeding period,the test period was lasted for 21 days,the digestion test was lasted for 5 days,the metabolism test was lasted for 8 days,during the test period,recorded the feed intake and observed the health status of each cattle for each day.The rumen fluid samples were collected during the test period to test the pH value,VFA concentration,dissolved hydrogen concentration and the dessolved methane concentration.Collect the fecal samples for the diet digestibility.The results showed that the addition of Mg in the diet could significantly increase the concentration of dissolved hydrogen in the rumen fluid of cattle.There was no significant difference in the feed intake,pH value and the total VFA concentration between the experimental group and the control group,while increased the propionate concentration and thus changed the composition of VFA in the rumen by the hydrogen.Hydrogen significantly reduced the rumen digestion of acid detergent fibers?P<0.05?,and the production of methane in the rumen was increased by the hydrogen?P<0.05?.The results indicated that increasing of dissolved hydrogen in the rumen reduced the ability of rumen degradation,changed the rumen fermentation mode and increased the rumen methane emission.2.Effect of hydrogen on the degradation rate of dry matter in the rumenThe aim of this part was to investigate the effects of hydrogen on the degradation rate of gry matter in the rumen.Materials and methods in this experiment are based on Experiment1.The feed samples were collected at the first two days of each week and stored at 65°C to constant weight.At the beginning of the trial period,the nylon bags containing the feed samples were placed in the net pocket at 0,24,48,60,66 and 70 h,and all the nylon bags were removed from the net bag after 72 h to stop the fermentation.The samples in the nylon were stored at 20°C for the degradation rate analysis.The results showed that the addition of Mg to the diet tended to reduce the rapid degradation of DM?P<0.10?,and significantly decreased the slow degradation rate of DM?P<0.05?.The effective degradation rate of DM in Mg group was significant lower than that in Mg?OH?₂ group?P<0.05?.The results showed that hydrogen can reduce the degradation rate of dry matter in the rumen.