Dietary magnesium sulfate supplementation protects heat stress-induced oxidative damage by restoring the activities of anti-oxidative enzymes in poultry. Choline Chloride is used as an important feed additive in livestock, especially poultry as it helps to maintain cell membrane integrity and normal maturation of bone cartilages, thus preventing perosis. In laying hens and quails, DL-carnitine supplementation slightly improves egg production and hatchability, but it mainly modifies egg composition. Albumen quantity and quality is improved and also albumen and yolk carnitine concentrations were enhanced, promising embryo development. Methionine not only serves as a constituent of body protein but also is involved in the development of the digestive tract and growth performance. Furthermore, it has a function of increasing muscle mass, feather development and improving egg production in poultry. Lysine is one of the most vital amino acids required in poultry nutrition. The main role of lysine is to participate in protein synthesis. Lysine is required for growth and maintenance, and it is considered a reference amino acid in the ideal protein diets. The inclusion of milk thistle in poultry diets increases their growth and productivity. Milk thistle components can improve immune response, antioxidant indices, kidney and liver function, blood hematology, lipid profile and then the physiological status of birds. Although the most important function of vitamin B 12 is in the metabolism of nucleic acids and proteins, it also functions in carbohydrate and fat metabolism. In growing chickens, a deficiency of vitamin B 12 results in reduced weight gain and feed intake, along with poor feathering and nervous disorders.