Probiotics, prebiotics, and synbiotics: an overview of their delivery routes and effects on growth and health of broiler chickens

The world population is drastically increasing, and it is evidently necessary to have more secure food supply systems. Poultry meat is one of the most cost-effective and most popular sources of protein. For decades, poultry producers have depended on preventative antibiotics to increase growth performance by establishing and maintaining healthy and functional gastrointestinal tract in young animals. However, these practices are currently under immense regulatory and consumer pressure for termination, due to the development of antibiotic resistance arising from overuse of antibiotics. Antibiotics need to be replaced by alternatives that have similar beneficial effects in terms of modulating the gut microbiome and improving the health and growth of the animals. Various groups of alternatives have been studied in poultry production, including prebiotics, probiotics, synbiotics, organic acids, essential oils, enzymes, and other novel compounds that are continuously emerging. Probiotics, prebiotics, and their combination (synbiotics) are gaining popularity among the different potential alternative products to antibiotics. In addition to evaluating the effectiveness of different groups of alternatives in the chicken industry, the techniques and methods for administrating those alternatives is also an important aspect that has been studied in order to obtain optimal results. Thus, proposing new strategies to maximise the effectiveness of different alternatives has been growing simultaneously with the proposed elimination of antibiotics from food animal production. This review focusses on the use of probiotics, prebiotics, and synbiotics as alternatives to antibiotics in the poultry industry, as well as descriptions of different application methods for delivering those alternatives to broiler chickens to maximise their effectiveness.