HOW THEY WORKCommonly, these are a sheepsized transparent polycarbonate box suspended above a race. When a sheep walks into the race, the chamber is lowered over it and the sheep is held inside for about 30 minutes. Air samples are taken during this time and the methane concentration is analysed.
WHY DO ITPortable chambers may be a useful method for screening a larger number of animals to identify naturally low methane emitting individuals. They allow large numbers of animals to be screened in a short period of time. This speeds up the animal selection process and provides more low-emitting animals from which to breed the next generation. Keeping the breeding pool large avoids restricting opportunities for general genetic improvements in the herd/flock.
CHALLENGESPortable chambers are not as accurate as respiration chambers as they only give a brief snapshot of an animal’s emissions and are still an artificial environment. It is important to achieve an airtight seal so that all methane produced by the animal can be measured. Intake is also not known accurately if used with grazing animals.
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Reducing New Zealand's agricultural emissions: How we measure emissions (edition 2)