The Methane Emissions From Beef Cattle Manure During Storage And The Effects Of Aspergillus Oryzae On Enteric And Manure Methane Emission From Beef Cattle And Its Mechanism

Methane（CH₄）is an important Greenhouse Gas（GHG）.Manure and enteric of beef cattle are main source of methane.In order to understand the methane emission characteristic from beef cattle manure during storage and development mitigation strategies of beef cattle manure and enteric methane,experiments were conducted as follows:Experiment 1: Methane emission rate from beef cattle manure was measured during short-term storage in spring,summer,autumn and winter by using the static chamber-GC with manual method in this study.Methane emission rate was continuously measured for 30 d in every season.Meanwhile,air temperature（Tair）and temperature at 10 cm below the manure surface（Tinside）were measured.The results showed that the daily mean Tair of spring,summer,autumn and winter were 18.89℃,28.51℃,22.87 ℃and 0.04 ℃,respectively.The difference of daily mean Tair were extremely significant among four seasons（P<0.01）.The Tair in winter was lowest than that in other seasons and the Tair in summer was highest than that in other seasons.Moreover,Tinside was correlated with Tair（R²= 0.97,P<0.01）.When the daily mean air temperature increased from 0.04 ℃ to 28.51 ℃,the daily mean methane emission rate during short-term storage increased by 151 times and the methane emission rates of manure has a positive correlation with air temperature and the equation could be described as y = 21.73e0.167x（R²= 0.83,P<0.01）.The results meaned that themperature is an important factor influencing the methane emission rates from manure.Experiment 2: It was measured by using the static chamber-GC with manual method that the methane emission rate from short-term natural storage（NS）and plastic sheet cover（CS）storage manure in spring,summer,autumn and winter.The results showed that the effects of plastic sheet cover on methane emissions rate were not consistent over time and temperature variation.The daily mean methane emission rate of CS in the first 19 days of spring（average temperature is 18.89 ℃）,13 days of summer（average temperature is 28.51℃）,10 days of autumn（average temperature is 22.87℃）were respectively decreased by 46.58%（P<0.01）,50.28%（P<0.05）and 42.82%（P<0.01）compared with that of NS.However,the daily mean methane emission rate of CS were significant more than that of NS from the 20 th,14th,11 th in storage of spring,summer and autumn,respectively（P<0.01）;The daily mean methane emission rate of CS were decreased by 40.03%（P<0.01）than that of NS during the whole experimental period in winter（average temperature is 0.04℃）.Conclusion: covering the manure with plastic can reduce methane emissions rate early on（first 10-19 days after piling）in the spring-autumn,and in the winter,but increase methane emission rate in the later period of storage in the spring-autumn.Experiment 3:This study was investigated to evaluate the effects of crude extracts of Aspergillus oryzae culture on rumen gas and methane production and fermentation characteristics such as p H,ammonia nitrogen（NH₃-N）and microbial crude protein（MCP）in vitro.The treatments include four groups（A,B,C and D）.Crude extracts of Aspergillus oryzae culture was added at levels of 0 m L,0.5 m L,1.0 m L and 1.5 m L to the A,B,C and D,repectively.In other word,Crude extracts of Aspergillus oryzae culture was added at levels of 0,8.38 mL·m L^-1,16.67 mL·m L^-1 and 25 mL·m L^-1 in artificial rumen fluid,respectively.The results showed that the total gas production for 24 h of C and D was significant higher than that of A（P<0.05）,but the total methane production for 24 h of C and D was extremely significant lower than that of A（P<0.01）.The differences of total gas production and methane production for 24 h were not significant beteewn B and A（P>0.05）;The p H was not affected by adding differen doses crude extracts of Aspergillus oryzae culture（P>0.05）;NH₃-N contents of C and D were significant lower than that of A（P<0.05）,but the MCP contents were significant higher than that of A（P<0.05）;The differences of NH₃-N and MCP contents were not significant beteewn B and A（P>0.05）.Conclusion: Total gas and MCP contents of rumen fermentation in vitro were significiantly increased by adding crude extracts of Aspergillus oryzae culture(≥16.67 mL·m L^-1).Methane productions and NH₃-N contents of rumen fermentation in vitro were significiantly reduced by adding crude extracts of Aspergillus oryzae culture(≥16.67 mL·m L^-1).Experiment 4:The objective of the experiment was to investigate the effect of Aspergiluus oryzae supplementation on methane emission,production performance and digestibility efficiency of nutrition of beef cattle.Eight healthy Simmental crossbred beef cattle（male,the beginning live weight 552.38±35.48 kg）were randomly and equally assigned to the experimental treatments:（1）control groups（CG,basal diet）;（2）Aspergillus oryzae grounp（AO,basal diet+6 g·（head·d）-1 Aspergillus oryzae）.The experiment included feeding experiment and manure methane emission experiment.The feeding experiment lasted 38 d.d1 to 25 for adaptation,d 26 to 30 for measurement enteric methane,d31 to 37 for feed intake,and digestion and metabolism experiments,and d 38 for ruminal sampling.Manure methane emission experiment lasted 45 d.In the later stage（d 29 to d 35）of feeding experiment,manure of experimental beef cattle was collected respectively.Two groups manure were stored on outdoor cement floor.Methane emission was measured by susing static chamber-GC with manual method.The results showed that there were not significant effects of Aspergillus oryzae on average daily gain（ADG）and dry matter intake（DMI）of experimental cattle（P>0.05）.But the gross profit per head per day of AO was increased by 29.30% than that of CG;The apparent digestible coefficient（ADC）of neutral detergent fiber（NDF）was significantly increased by 36.41% by adding Aspergillus oryzae in diet（P<0.05）.But there were not significant effects of Aspergillus oryzae on ADC of acid detergent fiber（ADF）and dry matter（DM）（P>0.05）;Enteric methane emission production and manure daily mean methane emission rate was extremely significant reduced 18.78% and 56.55% by supplementing Aspergillus oryzae,respectively（P<0.01）.The results suggested that Aspergillus oryzae as a methane inhibitor can be fed beef cattle in production practice.Experiment 5:In order to measure the effects of Aspergillus oryzae on rumen formation characteristics and microbial populations,eight healthy Simmental crossbred beef cattle（male,the beginning live weight 552.38±35.48 kg）were randomly and equally assigned to the experimental treatments:（1）control groups（CG,basal diet）;（2）Aspergillus oryzae grounp（AO,basal diet+6 g·（head·d）-1 Aspergillus oryzae）.After feeding 37 d,the rumen fluid was sampled for detecting the ammonia nitrogen（NH₃-N）,microbial crude protein（MCP）and volatile fatty acids（VFA）content and microbial populations.The results showed that Fungi and B.fibrisolvens as permillages of totle bacteria were increased in response to supplement of Aspergillus oryzae,respectively（P<0.05）;Protozoa and Methanogens as permillages of totle bacteria were decreased by supplementing Aspergillus oryzae,respectively（P<0.05）.Supplementing Aspergillus oryzae significantly decreased NH₃-N content in the rumen and increased MCP content in the rumen,respectively（P<0.05）.The content of acetate and butyrate of AO was higher than that of CG（P<0.05）,but there was no significant effect of Aspergillus oryzae on the propionate content and acetate: propionate ratio（P>0.05）.The results suggested that dirct-fed Aspergillus oryzae to beef cattle can significantly affect the Protozoa,Methanogens,Fungi and B.fibrisolvens as permillages of totle bacteria,and change the rumen formation characteristics.Above all,it seems better to avoid covering manure using plastic in the long-term storage to prevent development of anaerobic conditions which might result in extremely high methane emissions under high temperature.Enteric and manure methane emissions were decreased in beef cattle that received an Aspergillus oryzae supplement.The supplement affected microbial populations in the rumen and in manure,changing ruminal fermentation characteristics.Aspergillus oryzae is a effective feed additive for redusing the methane emissions from cattle.