An apparatus and related method for preparing grain for animal ingestion. The apparatus comprises an elongate cooking vessel having a rounded interior bottom portion and a rotating mixing and impacting assembly which extends longitudinally in the vessel from the inlet end to the outlet end thereof. The mixing and impacting assembly comprises: a center shaft; a plurality of mixing blades which rotate with and extend substantially parallel to the center shaft; and a plurality of elongate paddles which also rotate with and extend substantially parallel to the center shaft. The mixing blades travel beneath the grain surface level for stirring the grain material. The paddles are closer to the center shaft than are the mixing blades such that the paddles impact and displace the grain surface level.