The presented investigations were conducted on a group of 60 porkers of crossbreed Polish Landrace x Large White Polish. The animals were divided into two equal experimental groups. The control group (K) was fed diets without supplementation with probiotics, group (P) - diets with the addition of probiotic (0.2 kg t-1 feed). The aim of the study was to determine the effect of probiotic preparation on total numberof lactic acid rods from the