It should be noted that both eggs and meat of chickens are essential to human nutrition all over the world. In recent years, the modern poultry industry has undergone remarkable changes in its production methods over the past 50 years. Interestingly, intestinal microorganisms have evolved alongside the host, as gut health plays an essential and very important role for optimal production. When the health of the gut is negatively affected, the digestion and absorption of nutrients are also negatively affected, which has a bad effect on the feed conversionratio, that leads to an economic loss and increased exposure to different diseases. Thus, the microbial communities that live in the gut of chickens are essential for intestinal homeostasis and metabolism of the host, which will subsequently affect the physiological and health status.Clearly,the dynamic equilibrium, composition and good diversity of microorganisms are influenced by many environmental and management factors. However, microorganisms increase dramatically during the first weeks of a bird's life, and the corresponding colonization patterns appear to differ between laying and meat-type chickens.On the other hand, the gut microbiota and their relationship to health and productivity in both broilers and layingchickens are difficult to determine with precision due to the great variation between flocks, which arises due to many environmental and management factors that affect the microbial load of both beneficial and harmful bacteria alike surrounding birds.In this article, we will focus on the importance of microbial homeostasisin the alimentary canalof chickens and the various factors that affect this balance, and the results of these reactions on general health and productivity.