The aim of this study was to determine whether the administration of four different solid feeds would influence selected morphological and morpho-functional aspects of the rumen mucosa in veal calves. The fibrous supplementation of the liquid diet of veal calves has been provided by recent EU formulation (EC Council Directive 91/629/1991; EC Council Directive 97/2/1997). Twenty-five Holstein calves were assigned to either exclusively liquid diet (milk replacer, control), or pelleted feed, corn silage, extruded feed, dried corn silage. The morpho-functional effects of the fibre-containing diets were examined evaluating histological and histometrical characteristics of ruminal mucosa after the slaughter of calves. There were slight to severe histological abnormalities in the rumens of all animals examined. The severe histological abnormalities were present in calves given pelleted feed, corn silage, and extruded feed. Dried corn silage caused less ruminal damage. We found that the length and epithelial thickness of ruminal papillae were higher in control veal calves than in dietary fibre-supplemented animals. The results of the present study, even if partially, support the EU prescription in the use of fibre diets in veal calves as integration of the traditional milk replacer diet.