The aim of this review was to demonstrate beneficial microorganisms in different areas of animal production, including large animals, poultry and fish. Microflora or beneficial microorganisms are well defined by several authors as "effective dietary supplement" which have beneficial effect on host's health. Comparative studies were carried out on several species of animals administered " Beneficial Microorganisms (BM)" active beneficial microorganism-had revealed a bundle of merits and advantages for the host as compared with the flora normally exist in the gastro-intestinal tract. The benefits include food supplementation as well as the protection of the lost against pathologic agent. Moreover, BM act as a biological factor in modulation microbiome of the digestive system as well as the adjustment of the reaction with the environment and to create a useful development of immunity response. The use of effective organisms is a useful strategy that has a clear impact on improvement of growth and increase feed conversion efficiency and body weight ratio and health parameters in animals.