Answer:
Grass-fed beef is the most sustainable choice. Grass-fed beef represents a net gain for the human food supply because cows eat grasses that we can’t eat (from land that is typically unsuitable for human crops) and turn it into beef that we can eat.
Step-by-step explanation:
Cattle raised on a primarily foraged diet are termed grass-fed or pasture-raised; for example meat or milk may be called grass-fed beef or pasture-raised dairy. The term "pasture-raised" can lead to confusion with the term "free range", which does not describe exactly what the animals eat.
That said, grass-fed cows eat (mostly) grass, while grain-fed cows eat (mostly) an unnatural diet based on corn and soy during the latter part of their lives. To maximize growth, the cows are often given drugs, such as antibiotics and growth hormones.