yeah it's tough and nothing is easy (no ethical consumption and all that jazz). the good news for your pitbull is that dogs are a bit easier than cats from an ethical food perspective because they are great scavengers and unlike cats are not obligate carnivores. they're closer to people in that you can pretty easily replace some/all of meat they eat with starches and veggies. There is some very early new evidence that dog foods which are both grain-free + vegetarian/vegan might be bad for kidneys long-term, but the general consensus is that similar to people, reducing dogs' meat intake is good for them and better for other animals who would otherwise be bread and killed just for food.

If you don't feel comfortable reducing/replacing your pet's meat consumption, then consider donating to organizations trying to develop animal-free meat options and supporting regulations that allow lab-grown meats in stores. it's lib shit and not as effective as more direct action, but this is pretty much where i'm at with my cats till they pass or better options are available.