The investigations were conducted on 60 Holstein-Friesian dairy cows (at age 3 year and weight 590 kg) kept in tie-stall barn. The animals were divided into 3 groups of 20 heads each. The control group (K) was fed diets without probiotics, group (EM) –was fed diet with the addition of EM probiotic (dose of 150 ml × t^–1 TMR) and group (T) –was fed diet with the addition of ToyoCerin probiotic (dose of 0.2 kg × t^–1 TMR). Strains of Escherichia coli were isolated from faeces with the aim to determine their numbers, capability for hemolysis and assessment of their drug-resistance. The isolates were identified as E. coli on the basis of their biochemical properties API 20E (BioMérieux) and the PCR method. When analysing the capability of Escherichia coli for hemolysis, the highest number of haemolytic strains was determined in the faeces of animals fed diets with the addition of the EM probiotic. The examined isolates were characterised by different degrees of resistance to the antibiotics used in experiments. The smallest (P<0.05) number of resistant isolates was determined in group T.

43-50