One acer isnt going to provide grass for long it will be to dirt in no time. I have 3 acers of pasture for 3 horses. They arent out on it 24/7 they get up too 8 hours a day if we have enough rain to keep it growing. In our county its 2 acers a horse but iv gotten by with only 3 but it is well managed. My horses dont go out if its too wet and i keep them off it once it grazed down to a inch and a half tall. Plus we do weed control also its never ending work to keep it nice. Plus we mow it twice a year and keep the poop picked up.