I have concluded my hen has a vitamin A deficiency. (Her preen gland is all dried up). Everything I've read says to give her 2-3X the normal level for 2 weeks, however I can't figure out what the "normal level" is. I started giving her 3mls of nutri-drench once a day a few days ago. I'm not sure if this is enough. Should I buy vitamin A pills from the pharmacy? Or up the nutri-drench? TIA for your help! Background on the bird: 2year old barred rock, lowest in the flock. Started feather picking in December- I took away all treats and upped the protein with BOSS, meal worms, yogurt, and goat milk cream. Her feathers all grew back (feather picking stopped) but they feel grimy, dry, and brittle. On someone's suggestion I looked at her oil gland and its totally dry. I massaged it for prob 5min last night and the tiniest droplet barely came out, tonight it was back to dry.