Before tractors, almost the entire food chain involved animal slavery, since farms used draft animals. For that matter, even transportation was based on animal slavery (horses). Many of the sustainable and high performance fabrics like wool, silk, and leather are now replaced by synthetic fossil-derived plastics. But petroleum is also an animal product.
To be vegan, is to choose fossilized animal products and services over fresh.
there is a lot of weird things about what you’re saying, but for one:
the same amount or more petroleum would be spend on cultivating food for the to-be-slaughtered animals and transporting the meat around.
I’m not a vegan (anymore), but veganism is still the lesser evil here