what do you feed your yearlings?

I find myself emotionally drained..my yearling had heat in his front hooves this morning ..my pasture consist well of lots of clover or maybe just clover..the only feed he was on as he's growing is 1 cup of oats + 1 cup of BOSS and minerals AM and PM, I didn't give alfalfa or high protein feed as clover is rich in itself.. now I will have to omit the oats and we'll see what that does, if no improvement I will have but no choice to sell him :(

Can you test your hay/grass and then supplement with exactly what is missing?