Studies On Methane Emission Measurement And Predicting Model Of Beef Cattle

Livestock production is an important methane emission source. The population of cattle in China is huge, and contributes 70 percent of total livestock methane emission. This study designed different forage treatments and feeding levels to investigate beef cattle enteric fermentation methane emission rates, manure characteristics and manure methane emission fluxes, influences of main factors, then can quantify and evaluate the real effects of methane mitigation techniques more accurately, provide references for predicting beef cattle methane emission, contribute to the national ruminant methane emission inventory and provide scientific evidences for establishing strategies about methane emission control and mitigation.To explore the influences of major factors on methane emission from cattle manure, methane emission fluxes of beef cattle manure in different environmental temperatures and manure stack heights were measured by dynamic chamber method. Experimental results showed that the methane emission rate and cumulative emission during a 15-d ventilated storage period in 16℃was 0.031±0.002- 0.002±0.000 g·d-1·kg-1 manure and 0.17-0.18 g·kg-1 manure, 0.323±0.018-0.051±0.063 g·d-1·kg-1 manure and 3.8-5.1 g·kg-1 manure during 26-d a ventilated storage period in 25℃, 0.414±0.073- 0.033±0.050 g·d-1·kg-1 manure and 3.6-6.6 g·kg-1 manure during a 26-d ventilated storage period in 36℃. Manure methane emission rate in 16℃was significantly lower than the emission in 25℃and 36℃(P<0.01). The research allowed for development of empirical model that predicts methane emission from the stored manure for different manure stack heights. Reduce manure stack temperature and height properly to help reduce methane emission during storage.Twelve beef cattle were subjected to different feeding levels and forage treatments. Methane emission rates were determined by SF6 tracer method. Analytical results of this experiment showed that the enteric fermentation methane emission of cattle fed ammonia corn straw, silage and dry corn straw was 248.4±23.3, 234.3±19.4 and 261.7±20.7 L·d-1 respectively, there was significant difference between cattle fed silage and dry straw treatment with different feeding levels(P<005). The methane emission of cattle fed 1.43, 1.73 and 1.47M was 229.8±20.2, 248.3±14.2 and 266.4±20.1 L·d-1, respectively. There were significant differences among treatments with different forage treatments (P<005). Methane emission value increased when energy intake and dry matter increased. GE, DM and NFE daily intake can be used to estimate enteric fermentation methane emission rates from beef cattle.This study simulated 25℃environmental temperature, applied dynamic chamber method to measure manure methane emission rates and explore the influences of diets on methane emission from cattle manure. Experimental results showed that the manure stack methane emission rate and cumulative methane emission of cattle fed ammonia, silage and dry corn straw dietary with 1.19M and 1.47M feeding level was 0.015±0.009~0.001±0.001, 0.082±0.046~0.010±0.004, 0.018±0.004~0.003±0.003, 0.030±0.006~0.002±0.001, 0.065±0.014~0.005±0.001, 0.013±0.004~0.002±0.001 g?d-1?kg-1 and 0.20, 1.41, 0.27, 0.37, 1.13, 0.29 g·kg-1 manure during a 36-d ventilated storage period, respectively. The manure stack methane emission rate and cumulative methane emission of cattle fed ammonia, silage and dry corn straw dietary with 1.29M feeding level was 0.039±0.007~0.002±0.001, 0.073±0.007~ 0.001±0.001, 0.027±0.010~0.004±0.002 g·d-1·kg-1 and 0.19, 0.34, 0.28 g·kg-1 manure during a 21-d ventilated storage period. Forage treating mode had a great influence on manure methane emission rate, but energy intake had a minor influence.