Modulation of Swine Gut Microbiota by Phytogenic Blends and High Concentrations of Casein in a Validated Swine Large Intestinal In Vitro Model

Simple Summary The wide use of antibiotics as growth promoters poses a great threat to One Health, as the acquisition of resistance to antibiotics in bacteria leads to ineffective therapy of infectious diseases. That is why there is a need for alternatives for antibiotic growth promotors. Phytogenic blends are composed of various plant-derived bioactive compounds and are considered an alternative to antibiotics as feed supplements for improving production performance due to their beneficial effects on swine gut microbiota, resulting in improving the overall wellbeing of pigs. In this study, we used an artificial swine large intestine model to assess how two phytogenic blends and their combinations with casein affect swine gut microbiota. As a result, we observed that a combination of phytogenic blends and casein had the most promising effect as modulators of microbiota composition, as their supplementation caused an increase in the abundance of bacteria, which are associated with greater production performance in pigs. The results of this study showed promising feed additives for pig diet as replacement of antibiotics as growth promotors, which could have beneficial effects on growth performance, as the microbiota composition of pigs is directly correlated with it. However, the data should be proven in living pigs, as artificial GIT models do not fully reproduce the swine physiology.Abstract Phytogenic feed additives are gaining popularity in livestock as a replacement for antibiotic growth promotors. Some phytogenic blends (PB) positively affect the production performance, inhibit pathogens within the gut microbiota, and improve the overall health of farm animals. In this study, a swine large intestine in vitro model was used to evaluate the effect of two PBs, alone or in combination with casein, on swine gut microbiota. As a result, the combination of casein with PB1 had the most beneficial effects on swine gut microbiota, as it increased the relative abundance of some commensal bacteria and two genera (Lactobacillus and Oscillospiraceae UCG-002), which are associated with greater production performance in pigs. At the same time, supplementation with PBs did not lead to an increase in opportunistic pathogens, indicating their safety for pigs. Both PBs showed fewer changes in swine gut microbiota compared to interventions with added casein. In contrast, casein supplementation significantly increased beta diversity and the relative abundance of commensal as well as potentially beneficial bacteria. In conclusion, the combination of casein with PBs, in particular PB1, had the most beneficial effects among the studied supplements in vitro, with respect to microbiota modulation and metabolite production, although this data should be proven in further in vivo studies.