This collection features four peer-reviewed literature reviews on developing immunity in pigs. The first chapter provides an overview of the latest research in gut function and immunity in pigs, as well as the role of the gut microbiota in shaping intestinal immune responses. The chapter also reviews recent advances in the development of novel tools to investigate the function of the pig gut. The second chapter describes the enteric and mucosal immune systems of pigs and presents evidence from experimental studies of the links between the immune system and microbiota. It examines the microbiome and metabolism of pigs and highlights its importance in the development of pig immune systems. The third chapter reviews advances in nutritional strategies to boost immune function in pigs, including the use of lipopolysaccharide to stimulate the immune system. The chapter considers the need to reduce the use of antimicrobials in swine diets and reviews the effect of dietary supplementation during key stages of a pig’s life to enhance immunity. The final chapter assesses methods of improving gut function in pigs to optimise health, prevent pathogen colonization and optimise immunity. The chapter discusses research on genes associated with pathogen resistance and porcine immune response and reviews the role of dietary and nutritional strategies in preventing intestinal pathogen colonisation.