The effects of 1-h soaking, fermentation and phytase supplementation of a pig diet based on wheat and barley on ileal and total tract apparent digestibility in growing pigs fitted with a post valve T-caecum (PVTC)-cannula were studied. Eight animals in a two-period change-over design were used, subjecting four animals to each treatment (dry, soaked, microbial phytase supplemented or fermented diet). Acid insoluble ash was used as an indigestible marker for calculating apparent digestibility coefficients. Fermentation improved ( P<0·05) the ileal apparent digestibility coefficients of organic matter (OM), nitrogen and amino acids, while there was no effect of 1-h soaking and phytase supplementation. The total tract apparent digestibility coefficient of OM was also improved by fermentation. The ileal apparent digestibility coefficient of phosphorus (P) was higher for fermentation ( P<0·05) than for dry food and 1-h soaking. The total tract apparent digestibility coefficient of P was higher ( P<0·05) for treated food (soaked, fermented and supplemented with microbial phytase) compared with dry food. Fermentation improved ( P<0·05) the ileal apparent digestibility coefficient of calcium compared with dry and soaked food, and had no effect on the total tract apparent digestibility coefficient of calcium. Food inositol phosphates were affected by treatment ( P<0·05), with a reduction of P bound to inositol hexaphosphate (IP6) of 10% in the 1-h soaked food and of 80% in the fermented food. Degradation of IP6 in the gastro-intestinal tract of the animals was lower in the fermented food than in the other treatments. The content of neutral-detergent fibre in the food was reduced ( P<0·05) in the soaked and fermented food by 4% and 14%, respectively, compared with the dry food. In conclusion, fermentation of food can improve digestibility of OM, degrade IP6 and increase ileal digestibility of phosphorus, nitrogen and amino acids.