Methane Emissions from a Beef Cattle Feedyard during Winter and Summer on the Southern High Plains of Texas

Methane (CH4) emissions from enteric fermentation by livestock account for about 2.1% of U. S. greenhouse gas emissions, with beef and dairy cattle being the most significant sources. A better understanding of CH4 emissions from beef cattle feedyards can help build more accurate emission inventories, improve predictive models, and meet potential regulatory requirements. Our objective was to quantify CH4 emissions during winter and summer at a typical beef cattle feedyard on the southern High Plains in Texas. Methane emissions were quantified over 32 d in winter and 44 d in summer using open-path lasers and inverse dispersion analysis. Methane per capita emission rate (PCER) ranged from 71 to 118 g animal(-1) d(-1) in winter and from 70 to 130 g animal(-1) d(-1) in summer. Mean CH4 PCER was similar in January, February, and May (average, 85.0 +/- 0.95 g animal(-1) d(-1)) and increased to 93.4 g animal(-1) d(-1) during the June-July period. This increase coincided with increased dietary fiber. Methane loss ranged from 9.2 to 11.4 g CH4 kg(-1) dry matter intake, with lower values during winter. Gross energy intake (GEI) ranged from 135.2 to 164.5 MJ animal(-1) d(-1), and CH4 energy loss ranged from 4.5 to 4.9 MJ animal(-1) d(-1). Fraction of GEI lost as CH4 (Y-m) averaged 2.8% in winter, 3.2% in summer, and 3.0% overall. These values confirm the Y-m value currently recommended by the Intergovernmental Panel on Climate Change for Tier 2 estimates of enteric CH4 from feedlot fed cattle.