where are you located?
we did management-intensive grazing for 25 years here in southern west-central KY. With well-established forage base, adequate water, and sufficient fertilization, you can probably run one cow-calf pair per 2 acres...but you'd still be looking at purchasing hay and grain to feed through the winter...feeding period typically ran from early Nov. to May 1 here.
Back in the old days, once deer season was over, we opened gates and let the cows graze off the food plots...but in those days(and, yes, we ran cows in the woods back then), we were only planting food plots to draw deer in to shoot them in season, not really looking at year-round wildlife use.