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The intestinal tract is a host to 100 trillion of microbes that have co-evolved with mammals over the millennia. These commensal organisms are critical to the host survival. The roles that symbiotic microorganisms play in the digestion, absorption, and metabolism of nutrients have been clearly demonstrated. Additionally, commensals are indispensable in regulating host immunity. This is evidenced by the poorly developed gut immune system of germ-free mice, which can be corrected by transplantation of specific commensal bacteria. Recent advances in our understanding of the mechanism of host–microbial interaction have provided the basis for this interaction. This paper reviews some of these key studies, with a specific focus on the effect of the microbiome on the immune organ development, nonspecific immunity, specific immunity, and inflammation.

Background: Soy iso avone and soy saponin are heat-stable glycosides present in soybean meal, which is the major factor restrict soy protein using in aquatic feed. This study is aimed to conduct that dietary soy iso avone and soy saponin on growth performance, intestinal structure, intestinal immunity and gut microbiota community on rice eld eel (Monopterus albus), and revealed its mechanism. Results: In current study, dietary 1g/kg soy iso avone, 2g/kg soy saponin and their mixed feed decreased growth of M. albus. Dietary 1g/kg soy iso avone signi cantly increased serum alkaline phosphatase (P < 0.05), dietary 2g/kg soy saponin remarkably declined intestinal immunoglobulin M (P < 0.05). Dietary 1g/kg soy iso avone and 2g/kg soy saponin mixed feed signi cantly decreased intestinal complement 3, complement 4 and immunoglobulin M, amounts of intestinal goblet cells per root and shannon of gut microbiota (P < 0.05). Dietary 1g/kg soy iso avone, 2g/kg soy saponin and their mixed feed down regulated intestinal tight junction protein (Interleukin-12, Interleukin-15, Tight junction protein ZO-2-like) and anti-in ammatory (Interleukin-10, Transforming growth factor beta 2) mRNA expression, up regulated pri-in ammatory factors (Interleukin-1 β, Interleukin-6, Interleukin-8, Interleukin-12 and Interleukin-15) mRNA expression. Conclusion: Based on the current results, dietary soy iso avone and soy saponin could damage the intestinal structure and changes gut bacteria community of M. albus, and destroyed the intestinal barrier, eventually induced intestinal in ammatory occurring, soy iso avone and soy saponin mixed feed has more serious effect than they single supplemented.

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The objective of this experiment was to study the effects of catalase (CAT) on growth performance, antioxidant capacity, intestinal morphology, and microbial composition of yellow broilers. Male Lingnan yellow broilers (360), aged 1 day, were randomly divided into control group (CON) (fed with a basic diet), R1 group (fed with basic diet + 150 U/kg catalase), and R2 group (fed with basic diet + 200 U/kg catalase). Each group had 8 replicates and 15 chickens in each replicate. The test is divided into the early stage (1–30 days) and the later stage (31–60 days). The results showed that compared with the control group, groups R1 and R2 significantly (p &lt; 0.05) increased the weight gain and reduced (p &lt; 0.05) the ratio of feed to gain in the early and the whole stages; prominently increased (p &lt; 0.05) the concentration of total antioxidant capacity (T-AOC), the activities of CAT, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) in livers, the activities of CAT and GSH-Px in serum, and CAT in the jejunum in the early and the later stages; markedly increased (p &lt; 0.05) the villus height and the ratio of villus height to crypt depth of the duodenum in the early and the later stages, the villus height and the villus height:crypt depth ratio of the jejunum and ileum in the early stage, and significantly lowered (p &lt; 0.05) the crypt depth of the duodenum (in the early and the later stages), jejunum, and ileum (in early stage); memorably (p &lt; 0.05) increased the number of total bacteria and Bacteroidetes in ceca, as well as the number of Lactobacillus in the jejunum (p &lt; 0.05) on the 30th; significantly (p &lt; 0.05) increased the mRNA expression of junction adhesion molecule 2 (JAM2), mucin 2 (MCU2), and occlusal protein (occludin) in the duodenum in the early stage, and increased (p &lt; 0.05) the mRNA expression of JAM2 in the jejunum in the later stage. Collectively, adding catalase (CAT) to the diet of yellow broilers can improve the growth performance and the antioxidant capacity, promoting the integrity of intestinal morphology, optimizing the composition of intestinal microorganisms, and upregulating the mRNA expression of tight junction protein.

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Aim: This study was conducted to investigate the effects of dietary tributyrin (TB) and physterol ester (PSE) supplementation on the growth performance and intestinal health of weaned piglets. Methods and Results:Ninety-six piglets were randomly allocated to one of four groups, including a control group (basal diet), TB group (basal diet + 1500 g t −1 TB), PSE group (basal diet + 300 g t −1 PSE) and TB + PSE group (basal diet + 1500 g t −1 TB + 300 g t −1 PSE). All groups had eight replicates with three piglets per replicate.The experiment lasted for 28 days. The results showed that dietary TB supplementation increased (p < 0.05) average daily feed intake and average daily gain, as well as the acetate and butyrate concentration in ileum, and dietary PSE supplementation decreased (p < 0.05) the ratio of feed to gain (F/G) on days 1-14 of the trial. Dietary TB or PSE alone supplementation improved the ratio of villus height to crypt depth (VH/CD) and the expression level of Occludin in ileum. The linear discriminant analysis effect size analysis identified eight biomarkers in the control group, 18 in the TB + PSE group, two in the PSE group in ileum respectively. Correlation analysis showed that the relative abundances of Enterococcus, and Streptococcus were positively correlated (p < 0.05) with propionate concentration, while the relative abundance of Clostridium_sensu_stricto_1 was negatively correlated (p < 0.05) with acetate concentration in ileum. Conclusion:These findings suggest that dietary TB or PSE alone supplementation could alter the growth performance, intestinal morphology, microbiota community and metabolites of weaned piglets. Significance and Impact of the Study:Weaning stress is a major cause of slow growth and increased diarrhoea in piglets. This study demonstrated that dietary TB and PSE presented a beneficial role in growth performance and gut health via regulating intestinal morphology, microbiota composition and metabolites.

Epidermal growth factor (EGF) plays an important role in nutrients absorption. However, whether it can be an effective additive to improve the growth performance and nutrients absorption in lipopolysaccharide (LPS) challenged early weaning piglets is still unknown. A 14-days trial was conducted to investigate how EGF attenuates the effect of LPS on the growth performance, nutrient digestibility, microelement absorption of early-weaned pigs, and study the underlying mechanism. A total of 48 early weaned piglets, aged 25 days, were randomly distributed to four groups (control, EGF, LPS and EGF + LPS groups) consisting of a 2 × 2 factorial design. The main factors were the level of LPS (HLPS = high LPS: 100 μg/kg body weight; ZLPS = low LPS: 0 μg/kg body weight) and EGF (HEGF = high EGF: 2 mg/kg diet; ZEGF = low EGF: 0 mg/kg diet). Each group had four replicates and each replicate consisted of three piglets. The results showed that piglets injected with HLPS level significantly decreased the average daily gain (ADG), and significantly increased the feed conversion ratio (FCR) compared with the piglets injected with ZLPS level, while piglets fed HEGF level significantly increased the average daily feed intake (ADFI) compared with the piglets fed ZEGF level (p < 0.05). Piglets injected with HLPS level significantly decreased the apparent digestibility of crude fat compared with the piglets injected with ZLPS level (p < 0.05). Piglets injected with HLPS level significantly increased the concentration of most microelements in the gastrointestinal tract chyme and feces, and significantly decreased the expression levels of most microelement transport-relative genes in the mucosa of gastrointestinal tissues compared with the piglets injected with ZLPS level (p < 0.05). Piglets fed HEGF level significantly decreased the concentration of microelement in the gastrointestinal tract chyme and feces, and significantly increased the expression levels of the microelement transport-relative genes in the mucosa of gastrointestinal tissues compared with the piglets fed ZEGF level (p < 0.05). In conclusion, dietary EGF could attenuate the negative effect of LPS exposure on the apparent digestibility of crude fat and microelement absorption of early-weaning piglets. EGF and LPS influenced the absorption of essential trace element through changing the expression levels of microelement transport-relative genes in the mucosa of gastrointestinal tissues. In the early weaning piglets, EGF can be used as an additive to increase the essential trace elements absorption.