Jeffrey, it's not mandatory to finish cattle on grain. It's done only because the consumer demands it. Here on my island of Hawaii, there are several ranchers who now raise grass fed beef. There's
enough consumer demand to utilize all the beef our local slaughter house can handle. The movement here is to eat local, thus eat grass fed beef. Almost all the food stores now carry local grass fed. Why? Because their customers buy it.
The State of Hawaii has also taken the step to demand local foods for the school public programs. I don't what percentage they are up to, but it's higher than I thought it would be. And it's increasing. These local foods include grass fed beef.
The only beef I eat (except for the occasional prime rib dinner on special occasions) is local grass fed. The flavor is super. It's tougher than grain finished, but I deal with that by aging it at 35° to 40° F in my refrigerator for 5 days. If the slaughterhouse would hang it a few extra days, it wouldn't be so tough. But they are still learning about best methods, since the move to grass fed meats is fairly new here. Plus currently there is limited refrigeration space, so carcasses need to be pushed through.
Another point, there are breeds of cattle who finish on grass better than others. One local rancher imported dozens of British Whites, which do good on grass. Other local ranchers are now using the British White bulls In hopes that it improves their herds and carcass quality. Im seeing a lot of British White crossbreds in the pastures nowadays.
Bison are notoriously difficult to ranch, compared to cattle. Rather than switching to bison, I'd like to see public education about the benefits of grass fed beef. Make a demand for grass fed, and most of the feedlots will disappear or get a heck of a lot smaller. But then, the grain farmers will need to adjust to the lower demand for their product, meaning that a percentage will change to some other crop.