The extraction of high-value dairy proteins Such as lactoferrin and lactoperoxidase normally requires extensive pre-treatments of milk to remove fat and caseins by centrifugation, precipitation, Ca2+ chelation and/or filtration. Similarly, fat and caseins are normally removed prior to capture of recombinant proteins from the milk of transgenic animals. Such pre-treatments can result in significant loss of protein yield and/or activity. In this paper, we demonstrate that it is possible to pass significant quantities of raw, untreated milk through a 5 cm high XK16 chromatography column (volume 10 mL) packed with SP Sepharose Big Beads (TM) (GE Healthcare, Uppsala, Sweden) without exceeding the maximum allowable backpressure, provided that the processing temperature is kept nominally around milking temperature (35-37 degrees C). Results show that more than 100 column volumes of raw milk could be loaded at 300 cm/h before breakthrough of lactoperoxidase occurred. The dynamic capacity for adsorbing lactoferrin and lactoperoxidase simultaneously under these conditions was approximately 48.6 mg/mL of packed resin. Minor leakage (4.6% of the feed concentration) of lactoferrin occurred throughout the loading process but major breakthrough occurred only after approximately 100 column volumes were loaded. (c) 2005 Elsevier B.V. All rights reserved.