User blog comment:Sicknote45/The Elder Scrolls V: Dawnguard: Vampire Lord or Dawguard Defender/@comment-173.87.178.114-20120626172815/@comment-4747848-20120626205536

First you your vampire seduce on an enemy, then press your talk button. It should show "feed" or "talk" move it too "feed". There you go :)