To summarize: people have known that cows’ methane production can be reduced with an appropriate diet for quite some years. There has been a fair bit of searching for what that diet could be - tropical algae from high seas may produce the right outcome but aren’t readily available where the cows graze.
It is nice to learn that daffodils also do the trick, and reduce methane production by “at least 30%” (a cautious estimate, some results using artificial cow stomachs have given a reduction of 96%).
what’s the difference in methane production between cattle on feed versus allowing cattle to graze? we already know that feed corn and grain introduces a whole slew of gastrointestinal problems and health issues …
I wish I knew, but I can’t answer. Intuition suggests that they didn’t run the experiment with grazing cows, because then they wouldn’t have an overview of what was eaten, and how much was eaten - and measuring would be far more difficult.