Changes in Intestinal Microbiota, Immunity and Metabolism Caused by Mixed Lactiplantibacillus Plantarum and Bacillus Subtilis-Fermented Feed in Bamei Pigs

Abstract Background The Chinese pig breed Bamei faces numerous challenges, such as antibiotic abuse, feed shortages, weaning stress, low immunity and disease resistance after weaning. Probiotic-fermented feed is an ideal profile that can improve the intestinal microbiota, promote the digestion and absorption of nutrients, and improve immunity. However, the combined effect of long-term intake of probiotic-fermented feeds on the intestinal microbiota, intestinal metabolic profiles, and immunity in pigs is not well understood. Here, we investigated the effects of feeding basal feed, Lactiplantibacillus-fermented feed, Bacillus subtilis-fermented feed, mixed-fermented feed, and antibiotic-added feed for 100 days on the gut microbiota, immunity, and metabolism of Bamei pigs after feeding five different fermented feeds by using 16S rDNA high-throughput sequencing, enzyme-linked immunoassay, and untargeted metabolomics, respectively. Results 16S rDNA sequencing revealed that after the piglets were fed five different feeds for 50 days, the structure of the intestinal microbiota of the Bamei pigs was significantly altered, and feeding the mixed Lactiplantibacillus (L.) plantarum and Bacillus (B.) subtilis-fermented feed not only increased the α-diversity of the intestinal microbiota and the relative abundance of Lactobacillus, but also suppressed the growth of the conditional pathogens, Clostridium and Streptococcus. The Sobs and Shannon indices were significantly lower (p < 0.05) on Day 10 in Group A, which was fed feed supplemented with antibiotics. Feeding mixed-fermented feed not only significantly increased the production of anti-inflammatory cytokines, but also significantly decreased the production of several proinflammatory cytokines and inhibited the TLR4/MyD88/NF-κB inflammatory-related signaling pathway (p < 0.05), even more so than antibiotics. The results of untargeted metabolomics showed that feeding mixed-fermented feed improved the metabolism of Bamei pigs by increasing the content of narceine and alpha-cephalin; promoting bile secretion; and facilitating the synthesis of phenylalanine, tyrosine, and steroid hormones. ATP-binding cassette (ABC) transporters were significantly enriched in the antibiotic group. Conclusion The mixed L. plantarum QP28-1a and B. subtilis QB8a-fermented feed not only improved the intestinal microbiota structure and metabolic profiles and regulated the metabolic pathways of tryptophan, phenylalanine, and steroid hormone biosynthesis, but also improved the immunity of Bamei pigs. This research provides an ideal, healthful, and environmentally sustainable approach for Bamei pig breeding and conservation. Graphical Abstract