If grain is the only only choice, a local grain supplier might be a direction to pursue. Organic grain can be a hard to find local item but can be shipped to your door.
I had a small bull, a Lowline Black Angus keeping my back field mowed for 4 years until lightning took him this summer. Small breeds need considerably less space than a regular sized breed. They can be more expensive, but a Lowline can put on marbled beef on pasture alone. 2 acres kept him fat and happy most of the year. In the winter month he'd go through 3-4 round bales. I found a local guy who did not treat his hay field with any chemicals, I was happy to buy for just a few bucks more.
I always kept a sack of corn around in event of emergency. In 4 years I gave him 3, maybe 4 bags. He was short and black, and wanted the tall grass along the road. There are no streetlights on this road and the traffic goes pretty fast. This was a combination begging for an accident. I used the corn as bait to lure him back into the field when he broke through the fence until I figured out a leaf blower directed at his jewels will move him much faster.
In 2012 the Suwannee River flooded, rising to 85'. The water covered most of the back field leaving insufficient pasture to support the little guy. Just a little ways down the road is a grassy patch of field beside the electrical substation. I have a bagging mower for gathering grass and leaves for
compost. I mowed the patch, kept him in fresh grass for a couple of weeks. He'd eat 9 wheelbarrels of grass clippings every day. If I can't take him to the pasture, I can bring the pasture to him.