Establishment of hydrogen-utilizing bacteria in the rumen of the newborn lamb.

The development of hydrogenotrophic bacteria in the rumen of lambs was investigated by culture and labeling experiments. 14CO2 and 13CO2 incorporation by the rumen microflora of a 24-h-old lamb showed that while there was no labeled methane, double-labeled acetate was formed indicating the presence of hydrogen-dependent acetogenesis. In vitro counts from rumen fluid of 20-h-old lambs confirmed an extensive colonization of acetogenic bacteria while methanogens were absent. Methanogens appeared in the rumen of 30-h-old lambs, and as they developed there was a proportional decrease in the numbers of acetogens, indicating a competition for hydrogen between these two groups. Hydrogen-utilizing sulfate-reducing bacteria, which were established by the 3rd day after birth, did not seem to be affected by this competition.