Barb, your honesty and openess is one of the things I look forward to when I see you have posted something. You tell it like it is. I am so sorry you have had to go through all this with Bacca, I am sure it is heartbreaking. I know that your journey will help someone else at some point.
As for feeding, I do what has been suggested. When I have cooked something the dog and cat can eat I feed them that, but on my long days or when I am busy I feed commercial food. Don't know if this would work though because you will really have to be on top of the protien levels with the liver diet and Bacca's gut may not be able to handle the switching of foods all the time. My critters are used to this and so don't get D from it. Hang in there, I believe that by feeding him a liver diet you will see a big improvement and hopefully his skin will begin to clear up as well.
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The new vet that I found reminds me of you. He did an ultrasound of Bacca's gall bladder - no charge. He said it was for his own education. He has 2 Shelties himself and wants to learn what's up with Shelties and gall bladder.