You skipped over everything I've referenced and introduced a completely new narrative which has a simple rebuttal.
We waste tons of grains to filter through cows' bodies. Cows produce waste, that waste is used to replenish the land with minerals needed for grain growth.
Now, wouldn't the same thing be possible without filtering that waste through animals, keeping the waste in high amounts, suitable for the grain agriculture?
Of course, there's absolutely nothing magical in cow's butt that produces the necessary fertilizer. You can fertilize land with vegetable waste, producing less pollution and less non-recyclable waste, needing less energy.
The animal component is completely unecessary.
If you're trying to find rationality of these industries look at this narrative.
People hunted animals, they survived because of animals, but why did they do it, instead of just picking berries, raising food?
It was a time-saving heuristic. The animals were free, the animals were collecting nutrients, packing them into their bodies, and all that time was saved for the human. Humans just "collected" the neatly packed nutrients and had concrete savings.
Today, we bring the food to animals, we center everything around their food filtering, from an energetic, sustainable, environmental perspective it isn't equivalent, it's not even close. It is irrational. This irrationality is closely linked with our desire of excessive luxury.
From all the given evidence, dropping this would save us billions if not trillions in environmental cleanups, health-care bills etc.
Currently, there's nothing magical in animals that necessitates our use of them. The magic has disappeared when we snatched the planet.