Probiotics have become highly realized as additives for livestock because of their beneficial impacts on health and well-being. The current article aims to provide knowledge about the potential probiotic microbial strains referred to their relation to animal health. Lactic acid bacteria are the most regularly used microorganisms as probiotics, "besides other microbiota including certain fungi" which can be obtained from human, animal, plant, and environment. Not all microbiota be a good probiotic but there are main selection criteria for any potential probiotic microorganism. Nowadays, probiotics are used on large scale as growth promoters and productivity enhancers in both poultry and farm animals. Finally, the promising probiotic must achieve the safety status for humans or animals and lack of antibiotic resistance genes transfer.