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

Area of Science:

• Animal Science
• Environmental Science
• Agricultural Engineering

Background:

• Cattle enteric fermentation produces methane (CH4), a significant greenhouse gas (GHG).
• Accurate CH4 emission measurement is vital for climate change inventories and mitigation strategies.
• Public concern over climate change necessitates reliable methods for quantifying livestock emissions.

Purpose of the Study:

• To evaluate the accuracy and utility of a ventilated head box system for measuring CH4 and carbon dioxide (CO2) emissions, and oxygen (O2) consumption in cattle.
• To assess the impact of feed intake levels on CH4 emissions using the head box system.
• To determine the system's capability in capturing daily variations and emission peaks.

Main Methods:

• A ventilated head box system was employed to measure gas exchange in six Holstein heifers.
• Measurements were conducted during two ad libitum feeding periods (ADAPT, ADLIB) and one restricted feeding period (RESTRICT, 2% BW DM basis).
• Methane (CH4), carbon dioxide (CO2) emissions, and oxygen (O2) consumption were quantified daily.

Main Results:

• Methane emissions were significantly lower (P < 0.0001) during the RESTRICT period (193.2 ± 8.88 L/d) compared to ADAPT (235.0 ± 6.19 L/d) and ADLIB (228.3 ± 6.18 L/d).
• Carbon dioxide emission rates were 3627 ± 90.72 L/d (ADAPT), 3632 ± 90.47 L/d (ADLIB), and 3184 ± 104.79 L/d (RESTRICT).
• Oxygen consumption rates were 3391 ± 99.77 L/d (ADAPT), 3454 ± 99.57 L/d (ADLIB), and 3002 ± 111.36 L/d (RESTRICT).

Conclusions:

• The evaluated ventilated head box system provides an accurate method for measuring cattle emissions.
• The system can effectively differentiate emission rates based on feeding levels, with restricted intake leading to lower methane production.
• This technology offers valuable insights into daily emission variations and peaks, aiding in mitigation research.