The first chapter summarises the safety and efficacy of individual monocultures for prophylactic and/or therapeutic efficacy against Salmonella infections in poultry under both laboratory and field conditions. The chapter also considers the development of novel, cost-effective, feed-stable, direct-fed microbials with potential for widespread utilisation and improved production, delivery and clinical efficacy for animal use. The second chapter discusses the establishment of prebiotics as a series of feed compounds that serve as specific substrates for gastrointestinal tract (GIT) bacteria. The chapter reviews the impact of prebiotics on bird health, GIT function, and prevention of foodborne pathogen GIT colonization. Particular attention is drawn on the impact of prebiotics on the avian intestinal microbiome, cecal microbiome and the avian upper GIT. The final chapter considers current concerns surrounding the application of probiotics in poultry production, primarily due to mixed experiences of their effectiveness and lack of knowledge regarding the scientific basis for their modes of action. In contrast, prebiotics have been readily accepted by the sector. This chapter summarises recent research on the effects of both types of treatment, their possible modes of action, as well as the strengths and limitations of their use.