In the first experiment we verified methodical procedure for conducting an experiment in the experimental stable of Mendel University in Brno in Zabcice. Further at work we observed the influence feeding two forms of zinc (inorganic -- zinc oxide and organic -- zinc bonded to methionine) on digestibility of basic nutrients of diets, on blood parameters and body condition as indicator of monitored dairy cows health. Dairy cows were observed in transitional phase and during lactation. Dairy cows fed by diet with inorganic form of zinc (called group A), had average digestibility of crude protein, fat, crude fiber, nitrogen-free extracts and zinc lower than group with organic form of zinc in diet (called group O). For example group A had digestibility coefficient of crude protein 69.3 +- 7,80 % and zinc 60.4 +- 8.35 % during of the whole observation, while group O had digestibility coefficient of crude protein 75.0 +- 6.15 % and zinc 68.4 +- 5.57 %. Statistically significant differences are shown in the number of red blood cells (RBC) - group A had before calving, on day of calving, on 30th and on 60th day after calving statistically significantly higher (P <0.01) levels of RBC than group O, which had an effect on the value of hematocrit in the same period (P <0.05 and P <0.01) and hemoglobin on the day of calving and on 60th day after calving (P <0.05). Average daily intake of dairy cows were almost same. We observed lower decrease weight and body condition of dairy cows (group O). Group A decreased weight from 744.4 kg before calving on 610.8 kg on 60th day after calving compared to group O from 732.8 kg (before calving) on 646.9 kg (60th day after calving). It average fall condition about 0.8 BCS (group A), while only about 0.5 BCS (group O).