S. boulardii is an important microorganism, which has been the most frequently used as a safe probiotic additive in weaning piglets. Weaning is a critical period in the pig production cycle with a sudden, stressful, short and complex event due to the change in diet and a new living environment conditions [2], leading to reduce feed intake, increase the risk of environment result in gut inflammation, which affect morphological and function of intestinal, humoral immunity in the gut, tissue damage, intestinal microbial ecosystem and increase the incidence of diarrhea [20]. Previous study demonstrated more than two weeks must be required for weaning piglets to adapt to these changes. Therefore, in this study we investigated the effects of dietary S. boulardii mafic-1701 supplemented in the diet on piglet health and gut microbiota composition in a long term intervention.
In the present study, ADFI and ADG were not changed in the whole feeding trials. However, the result showed that weaned piglets supplemented with S. boulardii mafic-1701 significantly improved feed efficiency. In addition, as a positive control, in the whole period of the experiment, supplement aureomycin with the diet had significantly decreased F:G. these results suggested that the inclusion of S. boulardii mafic-1701 in diet could maintain similar feed efficiency as piglets fed the antibiotic diet.
Weaning piglets in CON exhibited diarrhea with semi-liquid or watery faces. During 0–14 days, compared with CON, ANT and SB were significantly decreased the rate of diarrhea. Interestingly, on days 15–28 and the overall experiment period did not markedly differ across three treatment groups. Obviously, diarrhea of piglets was not caused by the use of the antibiotics, in other word it was not antibiotic associated diarrhea. Thus it can be speculated that the diarrhea was relevant to post-weaning stress, although the exact underlying mechanisms remain unclear [21]. However, oral administration aureomycin or S. boulardii mafic-1701 could minimize the adverse effects of weaning stress during the first week, but the incidence and frequency of diarrhea was all decline and did not differ among three treatment groups during the whole 28 days. These results suggested that the piglets may be adapt to the new social and physical environment regardless of the diets.
It is generally known that the deleterious effects of weaning on the piglets gastrointestinal are vast, although the mechanisms by weaning influences intestinal function are less clear, it is certain that weaning could lead to drastic changes in breakdown of intestinal barrier functions [22]. The intestinal barrier is composed of intestinal epithelium cells and the tight junction proteins of epithelial cells [4]. The intestinal epithelium has a prominent and visible capacity for defensing against potentially harmful microorganisms as the first physical barrier line [23]. When the intestinal barrier is breakdown, it can result in pathogen microbiome colonization and takes with the risk of inflammation [24]. It is associated with the activation of innate immunity and inflammatory responses. In this study, we found that the concentration of pro-inflammatory cytokines such as TNF-α, IL-8 and IL-6 were decreased in ANT and SB compared with CON. We have also found that the production of IL-4 was increased by oral administration S. boulardii mafic-1701. These results indicated that S. boulardii mafic-1701 has beneficial effects on intestinal inflammation. Similarly, it has been previously shown that S. boulardii administration was significantly decreased mRNA expression of cytokines including interleukin-1β and interleukin-12 [25]. nuclear factor kappa B (NF-κB) is a pivotal regulator of innate immune responses in the gut [8]. Previous study has shown that S. boulardii blocked NF-κB activation and reduced colonic inflammation [26]. Thus, we can assume that S. boulardii mafic-1701 could alter the concentrate of pro-inflammatory cytokines through modulate the signal pathway implicated in pro-inflammatory responses such as inhibit the NF-κB associated pathways activation. Nevertheless, we do not exclude that exit other mechanisms could account for modulating effect of S. boulardii mafic-1701 on inflammatory responses. However, there is no doubt that S. boulardii mafic-1701 possess an anti-inflammatory property in the gut.
Previous study demonstrated that probiotics could activate the local mucosal protective mechanisms and exert beneficial effects on the host such as modulate anti-oxidation and immune responses [27]. In our study, we observed that S. boulardii mafic-1701 and aureomycin supplementation had no effect on increasing the levels of IgA and IgG in the serum. It was inconsistent with the previous observation by JEAN-PAUL, who reported that secretory IgA and secretory constituent of immunoglobulins in the rat small intestinal was increased by treated with S. boulardii [28]. Indeed, different probiotic strain could exert different physiological effects, therefore the differential immune response of piglets may be related to the type and does of probiotic strains we used. Besides, it is also associated with the animal models we chose to use in this study. In the future, the verdict need to be validated. Furthermore, in terms of antioxidant analysis. In our study, we found that T-SOD was increased in SB in the serum of the piglets, which suggested S. boulardii mafic-1701 plays a critical role to improve antioxidant capacity and protect intestinal mucosa [27].
The greatest and most diverse cluster of microorganisms was inhabited in the gut [29]. The gut microbiota has symbiotic relationship with the host, which provides an ideal survival environment for microbes while the microbes provide a broad range of functions for the host such as defense against pathogens, digestion of complicated dietary nutrients, production of beneficial metabolisms and maintenance of the immune system [29]. Diet can drive gut microbiota composition, for instance, Antibiotic treatment can alter the balance of compositional in the intestinal microbiota. In contrast, oral ingestion of probiotics can enhance this delicate balance between host and gut microbes. In fact, the core advantage of the probiotic is considered by supporting a stable immune system. Oral administration probiotics can improve gut health by stimulating the growth of some beneficial microbes and inhibiting pathogens invasion [30]. In present study, PCA indicated that diet is the most crucial factor contribute to changes in microbiota structure, considering that groups were matched for age, had no difference in environment and received no recent medication. Compared with the other regimens, oral administration of S. boulardii mafic-1701 was showed that the largest variety in microbiota in the cecum and colon samples. Namely, the composition and structure of the microbiota was greatly affected by diet. From the results of phylum analysis, we found that the cecum microbial floras were dominated by Firmicutes, this was consistent with previous finding reported by Lei Yu [31]. Whereas colon microbiota communities were dominated by Firmicutes and Proteobacteria, regardless of diet treatment. The colonization of Proteobacteria was increased in the colon that was expected because the members of proteobacteria are facultative anaerobes [32] and the colon is a completely anaerobic environment which could provide a favorable living environment for them [33]. From the results, we found higher bacterial diversity in cecum and colon of the piglets fed with S. boulardii mafic-1701 in the feeding trial. In cecum, one of the microbiota enriched in SB was Ruminococcaceae. In other word, the population of Ruminococcaceae genus was increased by dietary S. boulardii mafic-1701 administration. This should be associated with S. boulardii cell wall composition, the yeast cell wall consists of Mannose, chitin, 1,3-β- glucan and 1,6-β- glucan [8]. While Ruminococcaceae species may be have a wonderful ability to utilize simple and complex sugars and polysaccharides then the production of a certain amount of volatile fatty acids as an energy sources which can be utilized by the host [34].The result investigated that S. boulardii mafic-1701 inclusion had beneficial effects on giving a balanced gut microbiota with high stability in a long term intervention.
In the colon, S. boulardii mafic-1701 inclusion showed some alterations in regard to microbiota communities in weaned piglets. Bacillus is identified as a helpful microbe to modulate gut health, they can germinate to form metabolically active and with the ability to survive hostile environments [35]. Several species of Bacillus can reduce dextran sulfate sodium induced colitis and improve the production of SCFAs [36]. In this study, S. boulardii mafic-1701 inclusion increased the abundance of Bacillus genus. Previous study reported that several Bacillus species, which are considered to reduce pathogen colonization by unclear mechanisms [35]. Notably, the relative abundance of Clostridiaceae family was significantly increased in ANT compared with SB. C. difficile belongs to Clostridiaceae and is generally regarded as the most major etiologic factor for antibiotic associated diarrhea and colitis, C. difficile mediates intestinal disorder by releasing two potent exotoxins, toxin A and toxin B [37]. The diagnosis was further confirmed that antibiotic treatment altered the composition of the gastrointestinal microbiota, cause the gut dysbiosis that manifest the host susceptible to pathogen infection and trigger the immunological dysregulation [38]. In contrast, S. boulardii mafic-1701represents one of the most effective probiotic that have ability to treat antibiotic associated diarrhea and prevent pathogen infection [37]. Lactobacillus belongs to the phylum Firmicutes, class Bacilli, order Lactobacillales and family Lactobacillus [39], which is characterized by antibacterial and anti-inflammation activities. Previous study has reported that Lactobacillus spp. are beneficial to the host due to their underlying effects on gut function and health [40]. Nevertheless, the present study showed that the relative abundance of Lactobacillus genus was decreased in SB compared with CON. The reason for this result might be associated with the increased diversity of the microbiota induced by inclusion of S. boulardii mafic-1701 in diet [41].Moreover, the community of Lactobacillus in porcine intestinal would decreased in time [42]. Prevotella strains are negatively linked with chronic inflammatory conditions[43]. As we expected, a reduction on the population of Prevotella was observed in piglet supplied S. boulardii mafic-1701. Taken together, these observations further point to the beneficial effect of S. boulardii mafic-1701 on regulating the gut microbial ecology and S. boulardii mafic-1701 may be contribute to a lifetime health of piglets.
The intestinal microbiota is a signaling hub that integrates diet [44], meanwhile, diet drives intestinal microbiota composition and metabolism. A growing body work demonstrated that microbial produced metabolites as crucial executors to regulate the health on the host [29]. SCFAs play a central role in gut metabolism [45]. A previously published report indicated that probiotics can enhance SCFAs production [46]. In this study, we found that the production of valerate was significantly increased in ANT and SB compared with CON in the cecum. The finding demonstrated that S. boulardii mafic-1701 could enhance SCFAs levels and provided an evidence that S. boulardii mafic-1701 can substitution antibiotics to a certain extent. In addition, previous study showed that the major metabolites from the microbial fermentative activity are acetate, propionate, and butyrate [29]. In the present study, it’s worth noting that the production of colonic acetate, propionate and butyrate were significantly increased only in ANT, which might be associated with a number of factors, for instance, an increase in dietary intake is the most important element [46] and this hypothesis is accord with the results of growth performance which we investigated. And beyond that, the principal site of fermentation is proximal colon thus the production of SCFAs are depended on the numbers and the types of microbes which colonized in the colon [46].