Update: Phoenix is home!!!
I was driving to my parents' place last night, and I see a big white blur running as fast as she could (adrenaline, no doubt) down my block, eager and excited to be home. She might have been hit by a car and that's what took her so long to get here. It's a surface wound, luckily, so been keeping it sterile and medicated (yes I've been through this drill before with other pets, including a different Pyranees.)
As far as the current conversation is concerned, our pets eat a lot of farm fresh eggs and homemade milk kefir (I often give them leftover probiotic grains to help their digestion.)