Clinically healthy Polish Holstein-Friesian calves were divided into two groups: a control group (12 individuals) and an experimental group (12 individuals). The experimental group calves received a mixture of 20% water herbal extracts prepared from Urtica dioica, Hb., Hypericum perforatum, Hb., Melissa officinalis, Fol., Chamomillae recutita Anth., Calendula officinalis, Flos, and Plantago lanceolata, Fol. The mixture was given from the 2nd to 14th week of their life. Control calves received no addition of herbal extracts to their diet. Red blood cell count, white blood cell count, haemoglobin concentration, haematocrit value, and mean corpuscular volume were determined in the 4th, 9th, and 14th week of the experiment. The beneficial effect of the herbal mixture on the level of the examined haematological parameters was demonstrated in all tested weeks. In the calves from experimental group, a significantly higher red blood cell count, haemoglobin concentration, and corpuscular volume, and lower white blood cell count were found. There were no statistically significant differences in the haematocrit values between both groups.
