※ 질문하기질문내용. Animals are not good sources of food because they use too much land that could be used for growing food plants and they eat plants could be used for food. For example, a piece of land can produce five times as much protein if rice is grown on it than if the land is used to raise animals for food. Where conditions are right, then, we can procude three to five times as much food by using the land for growing food plants than for raising animals.