Additives in cattle nutrition allow for a positive influence on the rumen environment, fermentation processes, health and productivity of animals. The most commonly used are yeast, probiotics, organic acids and phytogenic additives. The aim of this paper was to provide summary information on individual feed additives and to present first results from in vitro testing of various feed additives for ruminants. Our results show a positive effect of yeast on the digestibility of especially fiber in roughage, without a negative effect on the rumen microbiome. Incubation with fatty acid esters resulted in a slight decrease in feed digestibility and at high doses a drastic decrease in the number of bacteria in in vitro rumen fluid. A positive finding is the potential of fatty acid esters to reduce methane-producing bacteria. However, further research is necessary to better understanding the long-term effects of various feed additive alternatives and to implement them more widely in practice.