How they work
Respiration chambers are animal-friendly closed circuit containers in which animals are contained while their gas output is measured. The New Zealand Animal Ruminant Methane Measurement Centre at AgResearch, part-funded by the NZAGRC, is a dedicated measurement facility, comprising 24 chambers for sheep and four for cattle. Since its opening in April 2011, over 6500 sheep and more than 750 cattle have been measured. After up to a week of acclimatisation in open-sided crates, the animals enter the respiration chambers which are made of perspex and arranged side-by-side so animals can see each other. Automated systems continuously sample the air entering and leaving the chambers, to measure the amount of methane formed by the animals. Temperature, humidity and air flow are continuously controlled.
Technicians top up each animal’s food and water at regular intervals, and remove dung and urine. Time spent in the chambers is generally restricted to two days. All animal experiments are subject to strict animal ethics approval procedures, and animals are monitored for their welfare in the chambers; if animals refuse to eat or show signs of distress they are released. If environmental conditions change inside the chambers, the chamber doors open automatically and release the animals.
Why do it
The ‘gold standard’ in scientific experiments is to keep every element of an experiment the same except for the one factor you are investigating, e.g. the type of feed. In methane research, animal respiration chambers are close to this ideal standard; researchers know exactly what is going into and coming out of an animal and can change the feed, compare the methane emitted from genetically-different animals, or test the effectiveness of a treatment, e.g. a vaccine.
Challenges
Animals can be kept in chambers for only a limited period of time, so measurements essentially provide only a ‘snapshot’ of emissions. To infer longerterm average emissions, say in different physiological stages e.g. pregnancy or lactation, scientists have to rely on repeat measurements.
The ability to keep things largely constant remains the prime advantage of respiration chambers – but also its main drawback as this does not reflect the real world. For example, in the paddock, different animals might naturally select a different mix of feed, and some may be naturally more active than others. In a chamber, they do not have that choice. Overall, chambers are the most precise measurement method but they are labour and resource intensive, and the number of animals that can be measured is limited by the number of chambers available.
Further reading





Methane as a greenhouse gas





NZAGRC-PGgRc methane research programme





Technical manual on Respiration chamber design (external website)