That doesn't need to stop us. We got pretty good with breeding animals for specific traits. So you could take dogs which are very massive and breed them until they yield even more meat. Just like we did and do with cows and pigs. Also it is possible to feed dogs on a plant based diet, so it wouldn't be that much more expensive. (Besides, meat is extremely cheap due to subsidies. It costs much more to have a plant based diet, especially if it's organically grown. You could also use meat scraps as it is also done for pet food. Further lowering the price.)