As the others have stated, genetics have to be there. With low grading genetics it doesn't matter how well you feed or manage them. With very good genetics, I've seen poor feed programs reduce performance but not effect the kill sheets.

Balanced nutrition is very important, but there is no magic blend of ingredients. As long as you have a normal level of starch in the ration the cattle should marble according to their genetic potential.

Cattle without implants will always grade much better, but I think you give up too many pounds of carcass on the same amount of feed for the economics to work.

You didn't say whether your premium was on a dressed basis or on a live basis, I'm going to assume it was on a dressed basis since the cattle appear to be sold on a grid. You also didn't say if the $11 was the net premium, or if the YG4 discounts still had to be taken off of that, I'll give it the benefit of the doubt and assume that was the net.

Doing some quick math: $11/cwt on 850# carcass is $93.5/head additional income. 90 additional days on feed, at about $2.15 per day for feed, yardage, and interest is $193.50 in additional costs; so it looks like additional costs exceed the additional income by $100/head.