From: Rabbi Moshe Sofer
To: Rabbi Eizik
The Chasam Sofer permits force-fed geese in which hair-like objects are found embedded in the esophagus, provided that upon inspection the two membranes are separated and the hair did not penetrate through the inner membrane. He relies on the Taz's ruling that force-feeding injuries are treated like illness-caused injuries, the inapplicability of the 'wild animals eat thorns' reasoning to confined geese, and the possibility that the apparent puncture is a natural growth; without bedikah or where an actual thorn is found, the animal remains forbidden.
Source: Shu"t Chasam Sofer YD §25