Abstract: A method of preparing mash for extrusion into animal feed pellets is provided. The method includes conveying the mash along the length of a pre-conditioning chamber while injecting steam at a first temperature into the pre-conditioning chamber to heat and pre-condition the mash. The pre-conditioned mash is then transferred from the pre-conditioning chamber to a conditioning chamber and is conveyed along the length of the conditioning chamber while injecting steam at a second temperature into the conditioning chamber. In one embodiment, the steam injected into the conditioning chamber is superheated steam and the second temperature is higher than the first. In another embodiment, the steam injected into the pre-conditioning chamber is superheated steam and the first temperature is higher than the second. The mash is discharged from the conditioning chamber for delivery to a pellet mill for being extruded into feed pellets.