From: Rabbi Moshe Sofer
To: Rabbi Yosef
Jewish cattle merchants sold calves to non-Jews who had them castrated and then repurchased them. The Chasam Sofer concludes the practice is technically problematic, involving at minimum a Rabbinic prohibition, but since there is a genuine sale and the merchants face significant financial loss, one need not actively protest against it.
Source: Shu"t Chasam Sofer CM §185