"Zubrin advocates that even early visitors raise their own food, both green and on the hoof."

Why bring animals? Way too expensive and troublesome to get off the surface, let alone to Mars. Even sending the animals as little vials of genetic material will still require a working lab at the destination and the time to grow enough stock before they are of any use. Much easier to stick to a vegetarian diet if you're colonizing space, because animals are an extraordinarily inefficient source of food, especially since they will be competing with life support resources.