The presence of oxygen in rumen liquor and its effects on methanogenesis



In situ measurement of O2 in the rumen liquor of cows, sheep and goats using a membrane-covered O2 electrode revealed the presence of up to 1630 nmol/l O2; O2 became undetectable immediately after feeding of animals. The effects of O2 on H2 production and methanogenesis in samples of rumen liquor were investigated using a mass spectrometer fitted with a membrane inlet system. Methanogenesis was totally and irreversibly inhibited after short term exposure (about 10 min) to 5 KPa (0·05 atm) O2; H2 production was unaffected. Glucose additions produced rapid transient increases in H2 levels and increased O2 uptake.