I have had my Hyline Brown Chooks for about 3 weeks and one got Crop Bound (Impacted Crop). I contacted the man I got the Hens from and he came out to have a look.
He was very helpful and said that it was the long grass in their enclosure that was getting stuck in the Crop and fermenting. He held the hen upside down and squeezed the huge crop (none to gently!!) and the poor hen puked up heaps of junk.
Does anyone have a cure?