Try to subject it to Ultrasonic treatment prior to grinding this will sonicate the structure for adequate particle size reduction using a hammer mill and attrition mill combined
I converted chicken Feathers to powder using Grinder. Feathers were first washed, defatted and then dried in a hot air oven at 60 degrees Celsius for two days. The feathers were then cut into small pieces and converted to powder with the help of grinder and the activity for keratinase enzyme was analyzed.