The invention concerns a microbial feed supplement comprising a lactic acid utilizing bacterium Propionibacterium jensenii P63 and at least one lactic acid producing bacterium selected from the group consisting of Lactobacillus rhamnosus, Lactobacillus paracasei, Lactobacillus farciminis, Lactobacillus plantarum Lp115, and mixtures thereof. The invention also concerns the use of microbial feed supplements in methods for reducing and/or inhibiting acidosis as well as a kit. Finally, the present invention also relates to an in vitro method for evaluating the effect of one or more bacteria on acidosis.