INTRODUCTION
Feed additives are products used in animal nutrition for purposes of improving the quality of feed and the quality of food from animal origin or to improve the animals performance and health. The initial use of antibiotics in diets arose from the discovery in the late 1940's, in the United States that including the fermentation products of Streptomyces aureofaciens (a strain of bacteria) in the diets of simple-stomached animals such as pigs and poultry resulted in growth responses (Frost, 1991).
It is important to make a distinction between antibiotics used in the treatment and prevention of disease in farm animals (prescribed therapeutic and prophylactic use) which differs from their use as feed additives to enhance growth (Castanon, 2007). As feed additives, antibiotics are used at low concentrations of 2.5-50 ppm (depending on the compound used). In the next 50 years, the use of antibiotics as feed additives in pig and poultry production became virtually universal. However, the possibility of developing resistant populations of bacteria and the side effects of using antibiotics as growth promoters in farm animals have been led to the European Union and United States ban on the use of antibiotics on farm animals as growth and health promoters.
This will have avoidable consequences for growth performance of birds in the poultry industry. Hence, an intensive search for alternatives such as probiotics, prebiotics, symbiotics, enzymes, toxin binders, organic acids, organic minerals, oligosaccharides and other feed additives has started in the last decade (Fulton et al., 2002). Phytogenics are a group of natural growth promoters or non-antibiotic growth promoters, derived from herbs, spices or other plants. In this context, the present research provides an overview of recent knowledge on the use of phytogenic feed additives in poultry diets and possible modes of action and safety implications