Construction and Operation of a Respiration Chamber of the Head-Box Type for Methane Measurement from Cattle

Simple Summary The aim of the present work is to describe the construction and operation of a respiration chamber of the head-box type for measuring methane emissions from bovines. Methane is a greenhouse gas 28 times more potent than CO2 in its capacity of producing the greenhouse effect and global warming. This gas is produced in considerable amounts by cattle as part of its normal digestion process; approximately 37% of the global anthropogenic methane emissions originate from the livestock industry. Measuring emissions of methane by cattle is necessary for inventory calculation and the evaluation of mitigation policies of this gas. The gold standard technique for measuring methane emissions from cattle is the respiration chamber; however, respiration chambers are expensive pieces of equipment that are not easily available for developing countries. Since a large proportion of the world's cattle population is in the developing countries, a cheaper option is necessary. A respiration chamber of the head-box type is an option because of its low cost and high accuracy in estimating emissions. This chamber can be used to determine in vivo methane emission factors for those countries that do not have full respiration chambers. It can also be used to conduct experiments to evaluate the anti-methanogenic effects of different compounds. This paper aims to describe the construction and operation of a respiration chamber of the head-box type for methane (CH4) measurements in bovines. The system consists of (1) a head box with a stainless steel frame and acrylic walls, floor, and ceiling; (2) a stainless steel feeder; (3) an automatic drinking water bowl; (4) a hood made from reinforced canvas; (5) an infrared (IR) CH4 gas analyzer, a mass flow generator, a data-acquisition system; and (6) a steel metabolic box. Six assays were conducted to determine the pure CH4 recovery rate of the whole system in order to validate it and comply with standards of chamber operation. The gravimetrical method was used for the recovery test and the recovery rate obtained was 1.04 +/- 0.05. Once the system was calibrated, measurements of CH4 were conducted using eight animals consisting of four Holstein cows with a live weight of 593.8 +/- 51 kg and an average milk yield of 23.3 +/- 1.8 kg d(-1) and four heifers with a live weight of 339 +/- 28 kg. The CH4 production values were 687 +/- 123 and 248 +/- 40 L CH4 d(-1) for cows and heifers, respectively. The CH4 yield was 19.7 +/- 3.4 g and 17.1 +/- 3.4 g CH4 kg(-1) of dry matter consumed for cows and heifers, respectively. These results are consistent with those reported in the literature.