The effects of purified non-starch polysaccharide (NSP) fractions (soluble, guar gum (SOL) and insoluble, cellulose (INSOL)) NSP fractions on digesta passage rate, retention time and voluntary feed intake was studied in grower pigs. Compared to control, adding SOL + INSOL increased digesta viscosity, slowed digesta flow rate and increased retention time in the total tract. Voluntary feed intake and daily weight gain reduced with SOL + INSOL NSP, compared to pigs fed the control diet. Reduction in voluntary feed intake associated with feeding high fibrous diet in pigs may be a direct effect of the fibre fractions slowing the flow rate of digesta through the gastrointestinal tract. Thus, reducing the negative effects of soluble and insoluble NSP may enhance feed intake and improve grower pig performance.