There is a lot of debate on grass fed vs grain fed beef. It has dawned on me, that while everyone is posting their "facts" on the issue, that some very important information is being ignored. That information happens to be the yield grades being compared and the genetics which results in them.
When comparing the health differences, are researchers are comparing A yield grade 1 or yield grade 4 against the grass fed beef? In comparing the time to finish, are they comparing a grass fed steer which would finish on grain at a grade 4 against a grain fed steer which is finishing at a grade 1?
A yield grade 1will have marbling, but much less extra fat than a yield grade 4 making the yield grade 1 a healthier product. Cattle finishing at a yield grade 4 generally have genetics which take longer to get marbling. This means that the "facts" in the debate can be misconstrued by researchers stacking the data by comparing against different genetic types.
You want to stack the data to show how much healthier grass fed beef is over grain fed? Compare and Angus grass finished carcass against a large , fatty, yield grade 4 carcass. Want to stack the data showing how more efficient feeding grain is? Compare times to finish that animal producing the yield grade 4 carcass against the Angus steer finished on grain.
When gaining information between feeding methods, unless the genetics are taken into consideration, the results will not be accurate. Either side of the grass fed vs grain fed debate can use genetic differences in stacking the data in their favor. Until such time as there is a study comparing cattle with the same genetic tendencies towards marbling and body fat, neither side of the debate can give an accurate report to the consumer about efficiency or health.