I use 3% of their weight per day in hay and it works out about right. maybe 2.75% is closer but I want to err on the high side so they don't run out while I am gone. Also allow for them putting on weight maybe figure next month at 590 or 600lb. Maybe you know what the protein and TDN is of your hay. If not or inadequate it helps to have a good tub out along with mineral. Good luck.
Jim at Dawn | 
Feeder calves
