We already know that there's truth behind the saying, “we are what we eat,” but this is also true for what we feed to our food! Just as a low-carb diet that's high in healthy fats is good for our bodies, what goes into the plants and animals in our food chain determines how healthy they are. Not every molecule that goes into our food crops and livestock gets passed on to us when we consume them, but chemicals, additives, and even the conditions the food is produced in contribute directly to the healthiness of that food.
That's why it's no surprise that natural, grass-fed beef has health benefits for us, although it does mean we must take a slightly different approach for our recipes.

Studies published by the U.S. National Center for Biotechnology Information in 2006 and 2008 showed the health benefits to humans of eating grass-fed beef over beef that was fed grain (and lots of other stuff).

They found that grass-fed beef contains more antioxidants, omega-3 fatty acids, CLA, TVA, minerals, and vitamins than beef fed on grains and other food. Steers in the study fed on grains and other feed types were so low in omega-3 concentrations that their meat didn't even qualify as a meaningful source! To quote the study:

“Only grass-fed beef reached the target of more than 30mg of long chain n-3 FA/100 g muscle as recommended by Food Standard Australia and New Zealand for a food to be considered a source of omega-3 fatty acids.”

The study also determined that the longer steers are fed grain instead of grass, the lower the omega-3 and CLA content of their meat.

Studies:
2006: “Effect of feeding systems on omega-3 fatty acids, conjugated linoleic acid and trans fatty acids in Australian beef cuts: potential impact on human health.”
2008: “Effects of conventional and grass-feeding systems on the nutrient composition of beef.”