Britesea
Sustainability Master
That lining also contains a substantial amount of pepsin. I dry and pulverize it and put into capsules for stomach upset.Gizzards are generally the place you'd find pebbles and such to help grind the feed. I cut them open, clean 'em out and peel off the thick lining inside.
"Bird gizzards are lined with a tough layer made of koilin, a keratinous material of 90% protein and 10% fat, to protect the muscles in the gizzard