Technical note: Evaluation of an enteric methane emissions measurement system for cattle

Through the process of enteric fermentation, cattle produce methane (CH4), a potent greenhouse gas (GHG). Growing public concern about climate change has increased the need for accurate methods of measuring CH4 emissions from cattle directly to improve emission inventories and evaluate emissions mitigation techniques. The present study evaluated a ventilated head box system capable of measuring CH4 and carbon dioxide (CO2) emissions, and oxygen (O-2) consumption from cattle. Six Holstein heifers were used to measure CH4 and CO2 emissions and O-2 consumption from 2 ad libitum intake measurement periods (ADAPT and ADLIB) and 1 measurement period (RESTRICT) with intake restricted to 2% of BW on a DM basis. Methane emissions during RESTRICT were significantly lower (P < 0.0001) than both ad libitum periods. Daily CH4 emission rates per animal were 235.0 +/- 6.19 L/d, 228.3 +/- 6.18 L/d, and 193.2 +/- 8.88 L/d for the periods ADAPT, ADLIB, and RESTRICT, respectively. Carbon dioxide emission rates were 3627 +/- 90.72 L/d, 3632 +/- 90.47, and 3184 +/- 104.79 L/d for the ADAPT, ADLIB, and RESTRICT periods, respectively. Oxygen consumption rates were 3391 +/- 99.77 L/d, 3454 +/- 99.57 L/d, and 3002 +/- 111.36 L/d for the periods ADAPT, ADLIB, and RESTRICT, respectively. The head box system evaluated provides an accurate method of measuring emissions from cattle and can provide information about daily variations and peaks in emissions.