Abstract: Here is provided a process for treating feather or animal fur characterized by throwing feather or animal fur into a pressure-resistant vessel, directly heating it under an elevated pressure by means of saturated steam or superheated steam, then rapidly discharging it into an atmosphere of lower pressure to puff it, and drying and cooling it if necessary. The feather or animal fur thus treated can be crushed without difficulty. It can be utilized effectively as a feed for domestic animals in the form of a mixture with other feeds or as a nitrogen source fertilizer.