If you eat beef products, you can’t do much better ecologically than grass-fed. Grass-fed means the cattle are raised and fed on pastures as opposed to in feedlots, where they're shoveled grains and antibiotics. Eating too many grains can boost the amount of E. coli in a cow’s stomach, which can sometimes lead to tainted meats and mass health scares.
So why would farms even bother to feed cows grain? Factory farms feed their livestock grain because the government provides large subsidies to farms that produce grains like soy and corn. These grains are rich in protein, which means they fatten up the animals. But the meat from grain-fed animals tends to be lower in “good fat” and higher in “bad fat.”
Research suggests that grass-fed beef, on the other hand, has more nutrients than grain-fed, specifically more beta-carotene, vitamin E and omega-3 fatty acids. Cows have naturally evolved to eat grass, not grains. Most cattle mature in the spring, and as their bodies grow, they eat newly-grown grass, which is chock-full of seeds and nutrients. These same nutrients are found in the meat you buy when you're looking to grill a steak.
But grass-fed isn't just healthier. Because the cows eat grass rather than corn or soy, the fertilizers and pesticides normally used on the farm to grow the feed aren't used at all. Rather than being cooped up with feed, the cows simply wander the pastures, which is more humane treatment for the animals. Farmers rotate their cattle through different pastures each year, which becomes a natural way to use and reuse land. When animals graze in a certain area, their manure fills that pasture. The manure disperses into the soil at a slow rate and naturally fertilizes it, making the soil healthy to grow more grass. The cows can then return to that pasture to feed.