The Effect of Prebiotic Supplements on the Gastrointestinal Microbiota and Associated Health Parameters in Pigs

SIMPLE SUMMARY: The gastrointestinal tract (GIT) is home to a large number of microorganisms, referred to collectively as the GIT microbiota. These microorganisms can be beneficial or potentially harmful to the host. Ensuring a high level of microbial diversity in the GIT, with a high abundance of beneficial and a low abundance of pathogenic microorganisms, is essential for host health. A healthy microbiota is vital at all stages of pig production; however, the post-weaning period is of particular importance. The post-weaning period is a phase during which intestinal dysbiosis can occur, providing an opportunity for harmful microorganisms to colonize and proliferate, leading to poor performance and even mortality. Different microorganisms have different metabolic capabilities, varying in the substrates they break down and the subsequent bioactive metabolites they produce. Therefore, the dietary substrates available to microbes have a significant impact on the microbial composition of the GIT and the subsequent metabolites produced. A prebiotic is a substrate selectively utilized by host microorganisms and conferring a benefit to the host. Prebiotics offer a therapeutic strategy in order to alter the composition of the microbiota, enhancing the proliferation of beneficial microbes and production of host-health-promoting metabolites, which can subsequently limit the proliferation of potentially harmful microbes. There is currently a broad range of different prebiotic classes. These vary in structure and composition and subsequently in the effects exerted on the microbiota. The current review is an overview of the different classes of prebiotics, their potential mode benefits, and the main findings from investigations utilizing them in the pigs’ diets to date. ABSTRACT: Establishing a balanced and diverse microbiota in the GIT of pigs is crucial for optimizing health and performance throughout the production cycle. The post-weaning period is a critical phase, as it is often associated with dysbiosis, intestinal dysfunction and poor performance. Traditionally, intestinal dysfunctions associated with weaning have been alleviated using antibiotics and/or antimicrobials. However, increasing concerns regarding the prevalence of antimicrobial-resistant bacteria has prompted an industry-wide drive towards identifying natural sustainable dietary alternatives. Modulating the microbiota through dietary intervention can improve animal health by increasing the production of health-promoting metabolites associated with the improved microbiota, while limiting the establishment and proliferation of pathogenic bacteria. Prebiotics are a class of bioactive compounds that resist digestion by gastrointestinal enzymes, but which can still be utilized by beneficial microbes within the GIT. Prebiotics are a substrate for these beneficial microbes and therefore enhance their proliferation and abundance, leading to the increased production of health-promoting metabolites and suppression of pathogenic proliferation in the GIT. There are a vast range of prebiotics, including carbohydrates such as non-digestible oligosaccharides, beta-glucans, resistant starch, and inulin. Furthermore, the definition of a prebiotic has recently expanded to include novel prebiotics such as peptides and amino acids. A novel class of -biotics, referred to as “stimbiotics”, was recently suggested. This bioactive group has microbiota-modulating capabilities and promotes increases in short-chain fatty acid (SCFA) production in a disproportionally greater manner than if they were merely substrates for bacterial fermentation. The aim of this review is to characterize the different prebiotics, detail the current understating of stimbiotics, and outline how supplementation to pigs at different stages of development and production can potentially modulate the GIT microbiota and subsequently improve the health and performance of animals.