If you need more than this, you will have to go to a reproductive vet.
Like Steeldog said, Zinc is a great supplement also (as is tribulus). So far, I have not found an oil with a greater Vitamin E content than Wheat Germ Oil, although Rice Bran Oil comes close.
A reproductive vet can 1) determine exactly what the problem is and 2) prescribe you some serious hormone therapy that goes beyond supplementation. The problem could be genetic, age, disease, etc. The deficiency could be anything from sperm malformation {which no supplement will correct} to the male just being old/malnourished {which supplementation can correct}.
If you're still not having success with your stud after feeding raw + supplementation, then I would suggest getting his sperm analyzed under a microscope by a true reproductive specialist (not an ordinary vet).
Good luck,
Jack