A study was conducted to compare the digestibility of organic matter (OM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), hemicellulose and nitrogen (N) and N balance in Mukota (M), Large White (LW) and the LW × M F1 pigs. Four male pigs of each breed, at proportionately 0·3 of their mature body weights, were randomly allocated to each of four diets in a cross-over design. The diets, which were formulated to contain similar levels of protein (ca. 160 g crude protein per kg) and energy (ca. 9 MJ metabolizable energy per kg), contained 0, 100, 200 and 300 g maize cob meal per kg, which corresponded to NDF levels of 276·4, 360·3, 402·9 and 523·5 g/kg dry matter, respectively. There was a negative correlation (P < 0·001) between the digestibility of OM, NDF, ADF and hemicellulose and the level of NDF in the diet. The digestibility of OM, NDF, ADF and hemicellulose decreased linearly (P < 0·05) with increase in the level of NDF among all three genotypes. There was a genotype × diet interaction on NDF and ADF digestibilities with digestibility in the LW decreasing faster (P < 0·05) than in the Mukota and LW × M F1 cross with increasing NDF. Both breed and level of maize cob meal affected N digestibility (P < 0·001), whilst the N retained per unit metabolic body weight was only affected by diet (P < 0·01). Increasing the level of maize cob meal beyond 100 g/kg, however, did not reduce N digestibility (P < 0·05). There was neither genotype nor dietary effect (P > 0·05) on N retained per unit N intake. These findings showed that the Mukota and the LW × M F1 cross were better able to digest the fibrous components than the LW. In addition, the Mukota and the LW × M F1 cross displayed an ability to retain protein to the same extent as the LW.