My point was not to say that what is now, has always been but that there is always a reason in nature why something happens.Well, I was actually referring to their consumption rate. Cattle today have been selectively bred to eat a lot, grow quickly and maintain a high soft tissue mass relative to their wildtype counterparts, and they inhabit an environment where food is not limiting, and thus their metabolism optimises for rapid, rather than complete, digestion. All animals do this. Whether it makes a difference to methane production I don't know, but my point was just that farming cattle is not some 'natural' thing that must be preserved exactly as it is today. Unless we accept that all man's activities are 'natural', then farming definitely isn't, and as for today's farming being the optimum, the Copernican principle states that it's safest to assume we are at some random point in a timeline - not at the end.
But back to your question, for which I had to resort to wikipedia. It varies a lot by region (as I'm sure all you cattle farmers know far better than I) but in general, I think we can say that ancestral cattle (aurochs) ate grass plus whatever higher-calorie plants were available. They do not seem to have generally existed in large herds, which suggests that their diet could be expected to be more diverse than today's cattle, since mass grazing reduces the browsable plant diversity. And of course they ate no processed food or manmade supplements. But mostly they ate grass.
You can increase the level of a plants resistance to insects but you’ll raise the lectin levels which would also be toxic for humans.
You can add something to cows feed but now you’re interfering with a complex system.
If you wanted to recreate life on mars but missed one vitamin, everyone would die.
I don't want corporations, driven by profit motive, in the name of doing good, meddling with complex systems in my food chain. I certainly would avoid beef if that is the case and perhaps, that is part of the plan. They’ve been trying to reduce red meat consumption for over a decade now.
Unfortunately it will be the poor who will be the lab rats here.