Design and construction of low-cost respiration chambers for ruminal methane measurements in ruminants

Ruminant animals contribute significantly to methane emissions in tropical regions. Nonetheless, there are few facilities available in those regions of the world for in vivo measurement of methane production in cattle. The aim of the present work was to describe the design, construction and operation of respiration chambers for in vivo measurement of methane production in cattle in Mexico. Locally available materials were used in the construction. Walls, roof and doors were constructed of thermic panels with two windows of acrylic at the front so the animal can be observed at all times. Chambers have an air volume of 9.97 m3. Air is drawn from the chamber at a rate of 500 L/min by the effect of mass action flow generators. Methane was measured in air samples with an infrared analyzer. Chambers operate under a slight negative pressure of around -500 Pa. Air temperature inside the chambers is kept at 23 °C with an air conditioner, while relative humidity is maintained at 55 % with a dehumidifier. Functioning of the chambers was evaluated in Bos indicus, Nelore cattle fed Taiwan grass (Pennisetum purpureum) and a concentrate (18 % crude protein), and measurements were made during runs of 23 h duration. Methane production was on average 173.2 L per day, while the emission factor was 17.48 L methane per kilogram o dry matter consumed. It concludes that this respiration facility is capable of measuring methane production accurately in cattle fed tropical rations.