But in New Zealand, one-third of these warming gases come from animals, in the form of methane. So researchers are trying something unique to lower New Zealand’s greenhouse-gas hoofprint: They want to change what goes on inside the stomachs of millions of sheep and cows. [...] One strategy used is to genetically engineer the microbes so they won’t make methane. Another is to give the sheep and cows some type of feed that the bugs won’t like.