Lactobacillus strains from sows improve swine appetite by reducing the pro-inflammatory cytokine concentrations

Lactational feed intake (LFI) is important for the efficiency of sow production. Previous studies indicated that the gut microbiota participated in host appetite regulation. The role of the gut microbiota, especially <i>Lactobacillus mucosae</i> LM1 and <i>Lactobacillus amylovorus</i> in LFI regulation of sows was proved in the previous study. However, it is unclear whether and how <i>L</i>. <i>mucosae</i> and <i>L. amylovorus</i> affect feed intake. Forty-nine sows with similar backfat thickness (15.81 ± 0.31 mm), parity (3.36 ± 0.16), and initial litter size (10.08 ± 0.10) were used in the current study. They were stratified into high- (H group; LFI = 6.37 ± 0.10 kg/d, <i>n</i> = 26) and low LFI (L group; LFI = 4.85 ± 0.15 kg/d, <i>n</i> = 23) groups. The performance data and fresh feces samples were collected. The differences in the gut microbiota of sows were analyzed. On d 110 of gestation, the relative abundance of the phylum Proteobacteria (<i>P <</i> 0.05) and the concentration of fecal endotoxin (<i>P</i> = 0.032) were lower in H group sows than in L group sows, while <i>L. mucosae</i> (<i>P</i> = 0.021) was the dominant strain in high LFI sows. Three strains, <i>L</i>. <i>mucosae</i> (L.M), <i>L. amylovorus</i> 1 (L.A1) and <i>L. amylovorus</i> 2 (L.A2), from the feces of high LFI sows on d 7 of lactation were isolated. Whole genome sequencing results showed these strains had probiotic properties. Then, 50 piglets (the commercial pig offspring from a three-way cross between Landrace × York gilts and Duroc boars) at 28 d of age (initial body weight = 7.38 ± 0.26 kg) and 32 germ-free (GF) mice at 28 d of age (initial body weight = 13.45 ± 0.77 g) were used as models to verify the role and mechanism of dominant strains in host feeding regulation. Two gavage experiments confirmed that these strains of <i>Lactobacillus</i> reduced plasma or colon pro-inflammatory cytokine concentrations (<i>P <</i> 0.05). These strains of <i>Lactobacillus</i> increased plasma glucagon-like peptide-1 (GLP-1) concentration in both animals and decreased the number of glucagon-like peptide-1 receptor (GLP-1r) positive cells in the colon of GF mice (<i>P <</i> 0.05). Taken together, these findings suggested that these strains from high LFI sows improved in host feeding regulation by increasing the GLP-1 level to lower the inflammation level when reducing the number of GLP-1r positive cells to inhibit the GLP-1 activation on the satiety pathway. These results would provide novel information to enhance the feed intake of sows during lactation and even treat anorexia.