Last year I seeded a new pasture with a 6 way cool season mix at about 15-20lbs/ac and I added about 2-4lbs/ac of alfalfa and red clover. Well, about 5 lbs of the grass grew and all of the alfalfa grew!   It looks like 15 lbs of alfalfa out there.  I am too nervous to turn cattle into it, so I have been haying it.  The alfalfa is too thick and chokes the grass out.  I inter-seeded another 5-10 lbs of grass about 10 days ago.
What do I need to spray to get the alfalfa and clover thinned and/or killed.  Should I have killed the alfalfa and clover before I seeded?