Is there a reason such research often works bottom-up, from cells to meat? Would it not also be possible to go about it top-down, starting from an existing anim

Is there a reason such research often works bottom-up, from cells to meat? Would it not also be possible to go about it top-down, starting from an existing animal species (pig, chicken, etc.) and modify it via breeding or genetic engineering such that what remains is mostly a walking muscle that can be used for meat production in a more ethical manner? In the end, true lab meat might be "cleaner" or the better solution. But in the meantime, reducing the cognitive abilities of such farm animals by breeding or gene-tech also seems like it could be an ethical alternative to reduce their suffering.