Lactobacillus-based probiotic compositions for inclusion in microbial-based products. In one instance, the microbial-based product takes the form of an animal feed additive. When used as a feed additive for animals, especially ruminants, and in particular cattle, the following benefits from the composition are noted: (i) improved milk yield in dairy cattle, (ii) improved milk composition in dairy cattle, (iii) increased weight gain-to-feed intake ratio in beef cattle (feed efficiency), and (vi) improved average daily weight gain. Both Lactobacillus strains MB101 having ATCC Accession Number PTA-121710 and MB102 having ATCC Accession Number PTA-121711 are particularly effective at producing these results. Another marked benefit of the compositions when used as an animal feed additive is inhibition of pathogenic growth including E. coli, Salmonella, Clostridium, Staphylococcus and Streptococcus.