Efficient food animal production relies on the overall maintenance of health in the animal and promotion of a balanced and efficient gastrointestinal tract. This can be quite complicated because balance in the gut depends on a healthy microflora balance. There are more than 1,000 bacterial species in the guts of food production animals, and these species are naturally balanced under normal conditions. However, in modern production the establishment of a healthy microbiome is often impeded by confinement and lack of beneficial microbes typically present in nature during development. To address these challenges, feed additives are often used to promote the establishment of beneficial microbes. Dietary fibers used in food animal production include a diverse range of different combinations of monosaccharides to form oligosaccharides, intended to target specific microbes capable of breaking down these sugars. The basic concept of using fibers to modulate the gut microbiome is that fibers can be developed to promote the expansion of specific beneficial groups of bacteria. This, in turn, promotes competitive exclusion of potential pathogens in the gut. At the same time, these beneficial bacteria positively stimulate the immune system and produce byproducts such as short-chain fatty acids which are used by the host and accelerate energy utilization. There is evidence that these interactions could also influence the gut-brain axis and have physiological effects. It is generally believed that dietary fibers and other prebiotics have positive effects on the establishment of important beneficial bacteria in the gut, such as Lactobacillus and Bifidobacteria. There is evidence to support this theory, but there is less evidence regarding ancillary effects of dietary fibers on the gut microbiome. It is also challenging to differentiate between bacteria which are truly commensal and provide some benefit, versus those that are opportunistic and have potential to exacerbate disease problems. For example, Escherichia coli comes in many forms, ranging from beneficial to deadly in the host. There is little to no evidence at the bacterial strain level regarding specificity of dietary fibers, and in general dietary fibers should not be specific to certain strains within the same species. Overall, more high-resolution microbiome studies (including functional) are needed, and platforms to assess multiple products in different combinations are desperately needed. There is immense potential in using dietary fibers to modulate the microbiome, and the current peer-reviewed publication landscape inhibits true dissemination of knowledge in this area.

Johnson, T.  2025. Fiber and the microbiome: what’s all the hype? 2025 Poultry Science Association Annual Meeting, Abstract 575S