the thing is you want the cattle eating grass for as long as they can.so your better off understocking your pasture than over stocking.the way i figure it youll be feeding hay 5 months out of the year.so thats 5 4 by 5 round bales pre cow a year.so if you have 12 cows thats 60 round bales a year.sheep can be ran 3ewes to a cow/calf.but there again if you overstock your going tobe buying alot of hay.if you can its best to buy alest 70acs.so you can have 20 or 30acs in hay ground.