Following the removal of antibiotic growth promoters in animal feed, various products have been suggested as alternatives to the poultry feed industry. Among these products some types of clay or derivatives were used as a natural supply in order to optimise performance. Clay is indeed abundant naturally, cheap, widely used by hens raised outdoors voluntarily or by ingesting earthworms and soil fauna insects. As an indication it was estimated that a laying hen kept outdoors consumes 10g of soil, 7g of plant and 20g of insects and worms per day. In further studies it was reported that soil ingestion can reach 30% of dry matter intake. Considering their specific absorption capacities of ions, clays are considered real molecular sieves. Various studies have concluded that clays promote a hygienic digestive tract, increase food retention time and contribute to improving water retention and reducing the moisture content of droppings. The use of clays was accompanied by positive responses in nutrient digestibility, weight gain and feed conversion ratio. Also the addition of clay enhances meat sensorial value and organoleptic characteristics, the cutting yield and meat processing abilities. The antimicrobial and antitoxic properties of clay were shown to improve the appetite and weight gain of chickens eating food containing aflatoxins. In laying hens literature states that the use of clay improves egg size, egg internal qualities, shell strength and wet droppings. Clay use is also reported to reduce mite infestation in hens and improve ambient conditions in animal husbandry with substantially lower levels of NH3 and CH4.