Right, you should monocrop Monsanto's latest patented seeds and douse the land with insecticide and herbicide rather than raise some ruminants on prairie land they've roamed for millions of years.
There definitely have not been billions of cows millions of years ago. There is simply not enough „prairie land“ for them. So in reality we grow the latest Monsanto monocrop to feed the livestock, because otherwise there is no way to meet the demand for all of that meat.
1B+ ruminants with similar size / digestive systems? (including buffalo, aurochs, rhinos, etc) Absolutely. There were 30-60 million bison roaming the Great Plains just 170 years ago (not far off from America's current ~90 million head) [1]. The size of ruminants in the ice age and prior was also much bigger than modern cattle [2] [3].
