Separation of feed mixtures and its effect on the production traits of growing-finishing pigs was studied in three experiments. In Experiments I and II the effects of different types of equipment to prevent separation in a silo were studied. Experiment III dealt with separation along a feed transport chain. Experiments I and II clearly demonstrated an increase in feed quality variation by filling a silo without any arrangement to reduce separation. The last feed to be extracted from a silo filled in this manner showed an increasing amount of small particles and contents of crude fibre and ash, a decrease in the bulk density and also in the digestibility of nutrients and in the performance of the pigs. Filling a silo equipped with chutes by an auger or pneumatically through a cyclone did not create separation problems, and consequently there were no differences between these treatments in the production experiments. Separation measured by particle size, bulk density or chemical composition was not noticeable along the feed transport chain (Experiment III). There was no effect on performance of the pigs of their location along the chain. © 1982.