From: Rabbi Moshe Sofer
To: Rabbi Feish
The Chasam Sofer rules that animals subjected to neck bloodletting need not be considered treifos, since the esophagus lies deep within the neck and cannot be reached by the procedure absent deliberate grasping of the simanim. Milk from such animals or mixed herds is likewise permitted, as one follows the majority and any genuine prohibition would have been publicized. The ruling rests on anatomical evidence from the Mordechai and Smak rather than sevara alone.
Source: Shu"t Chasam Sofer YD §21