Old question, but: it's worth noting that there is substantial variation in methane emissions even among ruminants such as cattle. And indeed, even among cattle, Succinovibrionaceae are associated with lower methane emissions. So quite possibly you don't need to do any engineering, though there are apparently a large number of (then) poorly described metabolic genes that might be relevant:

Lower emissions were accompanied by higher Succinovibrionaceae abundance and changes in acetate and hydrogen production leading to less methanogenesis, as similarly postulated for Australian macropods. Large numbers of predicted protein sequences differed between high- and low-methane-emitting cattle. Ninety-nine percent were unknown, indicating a fertile area for future exploitation.

Instead of sorting through all those proteins (which might be fun but would probably take a lot of work), it might be more effective and easier to simply make cattle rumens better places for low-methane bugs to live, if your goal is to reduce methane. Possibly unrelated to these bugs, but for example feeding seaweed to cattle affects their microbiome through antimicrobial activity.

The old adage in microbial ecology is often wrong but always helpful to remember: "everything is everywhere, and the environment selects". So set up an environment that selects for the kind of bug you want!

Old question, but: it's worth noting that there is substantial variation in methane emissions even among ruminants such as cattle. And indeed, even among cattle, Succinovibrionaceae are associated with lower methane emissions. So quite possibly you don't need to do any engineering, though there are apparently a large number of (then) poorly described metabolic genes that might be relevant:

Lower emissions were accompanied by higher Succinovibrionaceae abundance and changes in acetate and hydrogen production leading to less methanogenesis, as similarly postulated for Australian macropods. Large numbers of predicted protein sequences differed between high- and low-methane-emitting cattle. Ninety-nine percent were unknown, indicating a fertile area for future exploitation.

Instead of sorting through all those proteins (which might be fun but would probably take a lot of work), it might be more effective and easier to simply make cattle rumens better places for low-methane bugs to live, if your goal is to reduce methane. Possibly unrelated to these bugs, but for example feeding seaweed to cattle lowers their methane production by affecting their microbiome through antimicrobial activity.

The old adage in microbial ecology is often wrong but always helpful to remember: "everything is everywhere, and the environment selects". So set up an environment that selects for the kind of bug you want!