Abstract
Due to the threat and emergence of bacterial resistance against antibiotics, the use of in-feed antibiotics at therapeutic and subtherapeutic levels has been limited. Complete withdrawal of antibiotics as growth promoters (AGP) has led to poor gut health signs in chickens that include conditions like wet litter, intestinal bacteria overgrowth, poor growth performance, malabsorption and various diseases. Two of the most common alternatives to AGP are prebiotics and probiotics. Both prebiotics and probiotics have become the potential feed additives that improve the gut health, immune system and microbiota by various mechanisms of action, and enhance growth performance of chickens. The review discusses the modes of action like antibacterial, competitive exclusion (CE), and immunomodulatory properties of prebiotics and probiotics, particularly in poultry. In ovo feeding of prebiotics and probiotics with promising effect on growth performance and reduction of pathogens like Salmonella is also discussed in this review. However, it is necessary to conduct more research with prebiotics and probiotics as well as other feed additives to understand the detailed mechanisms of action and identify better alternatives for poultry production and health.