Licensed under a Creative Commons Attribution 4.0 International License This research aimed to evaluate the effect of live yeast additive to cattle ration on milk yield of dairy cows. The research was conducted on a dairy farm, on a sample of 265 dairy cows during winter. The dairy cows were fed with a feed containing live yeast of Saccharomyces cerevisiae species (CNCM I-1077). The dosage was 2 • 10 10 cfu/head/day. Milk yield and the components of milk were monitored for a three-month-long period-starting one month before the supplementation of yeast to feed and ending two months after. The addition of live yeast to cattle ration had a significant positive impact already in the first month on milk yield (+1.25 kg/day), and the amount of fat (+0.055 kg/day), protein (+0.057 kg/day), lactose (+0.056 kg/day) and milk solids (+0.170 kg/day) contained in milk (p <0.001). The general conclusion of the experiment is, that the Saccharomyces cerevisiae additive had an apparent positive impact on milk yield and milk components.