The aim of the research was to determine the influence of the type and structure of the feed on the selected production traits, the development of the digestive system and the metabolic profile of the calves. The study was conducted on the farm "Orlovnjak" on 30 Holstein calves which were divided into three treatment groups: a) a control (K) group which was fed with a pelleted mixture, b) first experimental (P1) group which received a mixture of pellets with 10% whole grain corn and c) second experimental (P2) group which received a mixture of pellets with 10% chopped alfalfa hay. Body measurements were performed on day 5, 31 and 62 after calving, while body mass measurement was performed immediately after the 31st and 62nd day of lifetime. After sacrifice for histological research purposes, samples were taken. Blood sampling was performed 31st and 66th, and the collection of faeces 66th day of calves' lifetime. There is a positive effect of treatment on the concentrations of urea and triglycerides in the blood 66th day of calves' lifetime, while the same was not observed in haematological parameters. In differential blood was found positive effect of treatment. Treatment positively influenced the morphometric values of the length and width of the rumen papillae, keratin layer thickness, the thickness of the rumen wall, the width and height of intestinal villi and crypt depth and width of the small intestine. The positive effect of the treatment was found in influence on the proportion of raw fibers in the rumen content was found. Based on the results it can be concluded that the addition of corn grain and chopped alfalfa hay in the pelletized mixture can be applied with a favorable effect on the development of digestive mucus and digestibility.