Cows eat grass. Humans use more calories digesting grass than they gain from eating grass, so cows are infinitely more efficient than humans at gaining calories from grass.
And there are places in the world where growing human food would destroy the land. Semi-deserts like Texas and Montana. Grazing cattle there is a good idea. Bison would be even better because the native prairie there is adapted to bison, but cattle are a close substitute.
But we eat a lot more cattle than Texas & Montana can support.
In my neck of the woods, the vast majority of the beef we eat is grass fed for most of their lives, but then grain finished. They only eat grain for the last month (out of 8 or so), but they put on most of their weight in that last month.
Here in the UK, pretty much 100% of cattle are grass fed. In the winter, when there isn't enough grass, they're fed on silage (which is basically just grass cut and baled while still green, which turns it into kind of grass sauerkraut, which smells exactly like you'd expect) and "draff" or "spent grains" (depending on where you are) which is the stuff left over from brewing beer or the pot ale that goes to make whisky.
It's all a pretty delicate balance, but ultimately what happens is you end up growing a bunch of things humans can't eat so that cows can shit solid gold all over the fields and chop it into the soil with their hooves.
We eat because there's six inches of earth on the ground, it rains, clover grows, and cows (and pigs) shit solid gold.
Totally wrong. A large fraction of commercially-grown cows are fed eponymous cow (field) corn, and require antibiotics so they are kept alive just long enough to grow and be slaughtered. Field corn is what takes up 5% of all land area in America.
you type like using land from semi-deserts isn't destroyed for meat production...
you need to plant, fertilize and apply pesticides to maintain grass! or do you think grass with sometimes 60% of protein per gram grows out of nowhere? or that the global grain production, which more than 85% goes into feeding livestock that it's sometimes 20 times less efficient to produce the same quantity of protein, can't be distributed to the population?
Ranches in Montana and Texas definitely do none of those things. It's native grass, running about 1 cow per acre. Fertilizer and pesticide for an acre would be way more expensive than the profit on 1 cow per acre.
I honestly can't tell what conclusion you want us to draw? The vast majority of cows raise for agriculture are not raised in the ways you describe. Beef is the leading cause of deforestation in the rainforest!
And there are places in the world where growing human food would destroy the land. Semi-deserts like Texas and Montana. Grazing cattle there is a good idea. Bison would be even better because the native prairie there is adapted to bison, but cattle are a close substitute.
But we eat a lot more cattle than Texas & Montana can support.