Book excerpt: "The pig production sector faces many challenges, including the need to improve feed efficiency to reduce emissions from manure, finding alternative methods to prevent the onset of diseases affecting swine, as well as ensuring that the welfare of pigs is consistent with consumer and regulatory agencies' expectations. Understanding gut microbiomes as targets for improving gut health offers a comprehensive coverage on the wealth of research on the porcine gastrointestinal tract, its key role in pig health and nutrition, as well as its implications for improving feed efficiency and growth. This collection details how optimising the gut microbiome can contribute to an overall improvement in pig health."--