Not knowing how else to link the info, I copied and pasted TwoCrows advice here:
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First, you need to keep her isolated by herself and no freeranging. Do not feed her anything that is not water soluable. So only her layer feed, dampened, maybe some hard boiled eggs drenched in yogurt. When her crop gets too bloated, you will need to "vomit" her to get that gunk out. It is poisonous. So hold her in one arm like a football and with the other hand, support her at the crop. Lean her forward only, beak down. Massage the crop till the gunk pours out her beak. Only hold her like this for 7 or 8 seconds. Tip her back up and let her catch her breath. Do it again. You may need to vomit her twice a day for a day or two, but that stuff will not move thru her and is toxic. Keep her confined until her crop emtpies over night.
Put apple cider vinegar in her water, 3 tablespoons for one gallon of water. Have her drink this for one week. Offer it to all the flock for a week. You can also put probiotics in the feed. The ACV will keep the yeast/fungal infection in the crop at bay.
She will not starve to death if she does not eat for a day. Keep this program up for several days til you get a hold of the sour crop.
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