Do not worm 4 week old chicks, they are too young to have worms. It's okay to start worming at 5-6 weeks old depending on your soil conditions.
As others have mentioned, it is shed intestinal lining and shed cecal lining, an indication of coccidiosis.
Use Corid and follow the instructions in Coach723's post above.
As others have mentioned, it is shed intestinal lining and shed cecal lining, an indication of coccidiosis.
Use Corid and follow the instructions in Coach723's post above.