Fascinating thread. I need to share some pictures I have of a hen that seemed to linger with an unknown illness. I chose to end her suffering.
-A two year old Australorp, went broody.
-Gave her a couple of eggs to sit on. She successfully raised a couple of chicks.
-Continued to seem "off" after the chicks were raised, never returned to her old self.
-Tried deworming her, antibiotics, just about everything I could think of. She'd start to perk up, then start acting dumpy again.
-After months of this, I noticed she was spending more and more time in the run, not free ranging. Found her beat up one day in the coop.
- I separated her with a buddy and babied her. She wasn't getting better. One day I picked her up and when held completely upright I noticed
her struggling to breathe. Made the decision to put her out of her misery after months of no improvement.
-Not sure what she had, didn't know what I was doing. So here are the pictures and maybe you can give me a clue. My guess is that her body wasn't metabolizing
the fat and the fat stores were squeezing her organs. LOL...seriously, just a guess

This is the actual color. Very yellow fat stores.
Would love to hear your thoughts!
Pic#1 Opening her up down the breast bone.
Pic#2 Fat wrapped around her intestines and gizzard. Had a healthy looking liver, kidney and lungs.
Pic#3 Here is the ova with the little eggs. She hadn't layed since going broody, it had been months.
Pic#4 Her gizzard was choked in fat. Upon opening it, it was full of food and looked healthy.