The present disclosure provides methods for processing pistachio shells based on cooled, e.g., cryogenic, grinding. In embodiments, such a method comprises grinding raw pistachio shells in a cooled compression milling system, e.g., a cryo-compression milling system, under conditions to provide ground pistachio shells having a D50 particle size in a range of from 10 μm to 600 μm. Animal nutrition products are also provided. In embodiments, an animal nutrition product configured to be ingested by an animal is provided, the animal nutrition product comprising ground pistachio shells having a D50 particle size in a range of from 10 μm to 600 μm.