I bought some heifers back in October of last year the average weight was 545 lbs. I have been feeding the about 6 lbs of a good 12 to 14 % feed each. I am planing on putting them on good pasture in March. And putting a bull on them the first of May. My question is. Should i keep feeding them grain after i put them on pasture ? And how old would you guess the heifer's might have been when i bought them in October ?