Table 1.

Effects of microflora intervention on intestinal mucosal immunity in pigs.

Age of pig	Breeds of pig	Microbial species	Mode of intervention	Design	Conclusions	Reference
6 to 20 d	Landrace × Yorkshire crossbred piglets	Lactobacillus gasseri LA39	Oral administration	Control group - oral PBS, LA39 - oral administrated of bacterial suspension (L. gasseri LA39 in PBS)	LA39 activates the oxidative phosphorylation pathway and increases the energy production in porcine intestinal epithelial cells	Hu et al. (2018c)
6 to 20 d	Landrace × Yorkshire crossbred piglets	Lactobacillus frumenti	Oral gavage	Control group - sterile PBS, L. frumenti group - PBS suspension containing L. frumenti (108 CFU/mL)	The levels of intestinal sIgA, intestinal tight junction protein (including ZO-1, occludin and claudin-1) and interferon γ were significantly increased in L. frumenti group	Hu et al. (2018a)
1 to 14 d	Duroc × Landrace × Yorkshire crossbred piglets	Chinese adult Jinhua pigs faecal microbiota suspension	FMT	FMT group - oral FMT, control group - orally inoculated with sterile PBS	FMT promotes IAA production in colonic lumen, enhance the activation of AhR and up-regulates IL-22 expression	Geng et al. (2018)
Days 70 and 100 of gestation	Large White × Landrace pregnant sows	Highly feed-efficient pigs faecal microbiota suspension	Gastric intubation	FMT group - FMT on d 70 and 100 of gestation	FMT group offspring have more goblet cells in the intestinal villi	McCormack et al. (2019)
1 to 28 d	Large White × Landrace piglets	L. plantarum ZLP001	Add freeze-dried L. plantarum ZLP001 to diet	Treatment group supplemented with freeze-dried L. plantarum ZLP001	L. plantarum ZLP001 significantly enhanced expression of the 6 HDP in the jejunum	Wang et al. (2019c)
1 to 20 d	Landrace × Yorkshire piglets	L. plantarum 299v	L. plantarum 299v dissolved in 2 mL of 0.1% peptone	Probiotic groups were given L. plantarum 299v dissolved in 2 mL of 0.1% peptone daily	Probiotic groups lower diarrhoea incidence, pBD2, pBD3 and ZO-1 expression increased in jejunum and ileum	Wang et al. (2019e)
20 ± 2 d	The offspring of L 359 boars mated to Camborough females	Clostridium butyricum	Add C. butyricum to the pig diet	Add 1,250 × 108 CFU/kg, 2,500 × 108 CFU/kg and 3,500 × 108 CFU/kg C. butyricum to the diet of the treatment group	The depth of crypt and the width of villi increase with the dosage of C. butyricumto	Casas et al. (2020)
1 to 3 d	Duroc × Landrace × Yorkshire piglets	Fecal microbiota from gestation sows combined with C. butyricum and Saccharomyces boulardii	Oral administration	FMT-CS group - gestation sows fecal microbiota combined with C. butyricum and S. boulardii	Early-life intervention significantly increased the alpha diversity of gut microbiota and plasma IL-22 and IL-17	Xiang et al. (2020)
1 to 6 d	Duroc × Landrace × Yorkshire piglets	Maternal FMT	Oral administration	FMT group-3 mL maternal fecal microbiota solution (>10 9 CFU/mL)	Increase of Blautia and decrease of C. sensu stricto in the relative abundances	Lin et al. (2018)
1 to 2 d	Danish landrace ×  Large White × Duroc	Colon microbiota suspension of suckling piglets	Oral + rectal administration or rectal FMT	Cesarean delivered preterm pigs were administered combined oral + rectal or rectal FMT	Only rectal FMT increased the stomach-to-colon pH gradient and resistance to mucosa bacterial adhesion	Brunse et al. (2019)
1 to 10 d	Yorkshire piglets	Min sows (an indigenous pig breed in China) fecal microbiota suspension	Oral inoculation	Recipient group: oral FMT; control group: orally inoculated with sterile physiological saline	On d 21, the relative abundance of the Proteobacteria was reduced; the concentrations of IgM and IgG in the jejunal mucosa, and that of IgG in the ileal mucosa of the recipient group, were increased	Teng et al. (2020)

PBS = phosphate buffer saline; sIgA = secretory immunoglobulin A; ZO-1 = zonula occludens 1; FMT = fecal microbiota transplantation; IAA = indoleacetic acid; AhR = aryl hydrocarbon receptor; HDP = host defense peptide; pBD = β-defensin; IgM = immunoglobulin M; IgG = immunoglobulin G.