Currently, studies have been carried out to verify the factors affecting the development and composition of the intestinal microflora of birds, as well as its relationship with the host organism. Research has estimated in the intestinal microflora a diversity of hundreds of varieties of microorganisms, where facultative aerobic bacteria prevail. Therefore, several studies have used modern techniques at the molecular level to analyze the intestinal microflora of birds, to identify the main constituents of this microflora, to establish its functionality and to monitor the dynamics of the intestinal microflora of birds. For example, the temporal changes occurring in the gut microflora of chickens with the effects of formic acid, propionic acid and chain fatty acids added to the diet and under the influence of heat stress were compared. Also, the composition of the intestinal microflora and the immune system of birds can be modulated by special feeding, mainly by the use of supplements and food additives. They confer general health benefits in the growth performance of birds, while modulating the gut microflora. Dietary supplements are used in bird nutrition and provide benefits such as competitive exclusion, gut maturation and integrity, immune system regulation, inflammation prevention, metabolism improvement and gut microflora modulation. Other food ingredients that promote microflora modulation are responsible for selectively altering the composition and metabolism of the gut microflora. Another dietary supplement widely used in microbial modulation is phytogenic additives derived from plants. Their use in food rations improves food quality and safety, as well as contributing to health status, acting as immunomodulators, antioxidants, digestive stimulants and substances that can increase the performance and quality of animal products. Moreover, the compounds of plant origin trigger the increase of mucus secretion in the intestine, which prevents the possibility of bacterial and fungal adhesion to the epithelium in the intestine of birds, as well as improves the physiological state and modulation of the intestinal microflora. Therefore, modulation of the intestinal microflora of birds through dietary supplements promotes beneficial intestinal health of birds, which interacts with the intestinal mucosa and other components to ensure the proper functionality of the body's vital systems, maintaining the health, well-being and performance of the birds.