The Effect Of Dietary Lactobacillus Rhamnosus GG Supplementation On The Immune Function And Gut Health In Weaned Piglets Challenged By Rotavirus

This experiment was conducted to investigate the effect of dietary Lactobacillus rhamnosus GG (LGG) supplementation on the immune function and intestinal health in the weaned piglets challenged by rotavirus (RV). A total of 24 healthy crossbred (Duroc×Landrace×Yorkshire) piglets (6.69±0.32 kg) weaned at 21 d were assigned to one of four groups (n=6/group) in a 2×2 factorial design experiment. Piglets were fed with the two diets supplementing LGG levels of 0 and 109 cfu/kg (namely two groups per dietary treatment) for 19 d. On d 15, all piglets were orally infused with RV or sterilized MEM medium. The results were listed as follows.(1) RV challenge enhanced the diarrhea rate, average diarrhea index, feed/gain and serum UN level in the piglets (P<0.05). RV challenge also increased the RV-Ab content of the duodenum, jejunum, ileum and serum, and the NSP4 content of the duodenum, jejunum and ileum in piglets (P<0.05). Dietary LGG supplementation reduced the diarrhea rate, average diarrhea index, feed/gain and the serum UN level in the piglets (P<0.05), and improved the effect of RV challenge on the serum UN level in piglets (P<0.05).(2) RV challenge reduced the CD4+T/CD8+T and the cell percentage of CD3+T and CD4+T in the blood, decreased the serum IFN-y, IL-4, IgG and IgA levels and the jejunal IFN-y, IL-4 and sIgA levels (P<0.05), and increased the IL-2 levels in the serum and jejunum of piglets Dietary LGG supplementation enhanced the cell percentage of CD4+T in the blood (P=0.09), and increased the serum IgG and IL-4 levels and the jejunal slgA, IFN-y and IL-4 levels in piglets (P<0.05). In addition, dietary LGG supplementation could attenuate the effects of RV challenge on the IFN-y, IL-2, IL-4 and sIgA levels in the serum or jejunum of piglets (P<0.05).(3) RV challenge reduced the villus height and v/c of the duodenum, jejunum and ileum (P<0.05), enhanced the crypt depth of the ileum in piglets (P<0.05). Dietary LGG supplementation enhanced the villus height and v/c of the duodenum, jejunum and ileum (P<0.05), and reduced the crypt depth of the jejunum and ileum in piglets (P=0.08). Dietary LGG supplementation could improve the effects of RV challenge on the villus height, crypt depth and v/c of the jejunum or ileum in piglets (P<0.05).(4) In the control group, RV challenge widened the gap between epithelial cells, and lead to the chromatin of the epithelial cell gathering toward edge and the partial organelle necrosis or dissolving in the jejunal epithelium of piglets. However, in the LGG supplementation group, the epithelial cells lined up tightly, the chromatin of epithelial cells distributed equally, and the less organelle appeared necrosis in the jejunal epithelium of piglets challenged by RV. It is possible that dietary LGG supplementation could alleviate the effects of RV challenge on the ultrastructure of the jejunal epithelial cells in piglets.(5) RV challenge downregulated the gene expression of ZO-1, occludin, Bcl-2, MUC1 and MUC2 (P<0.05), and enhanced the gene expression of Bax in the jejunal mucosa of piglets (P=0.06). Dietary LGG supplementation upregulated the gene expression of ZO-1, occludin, Bcl-2, MUC1 and MUC2 (P<0.05), and reduced the gene expression of Bax in the jejunal mucosa of piglets (P<0.05). Additionally, dietary LGG supplementation could also attenuate the effect of RV challenge on the gene expression of Bax in the jejunal mucosa of piglets.(6) RV challenge increased the pH and the Escherichia coli counts of the ileal and cecal digesta (P<0.05), and decreased the Lactobacillus (P<0.05), Bifidobacterium (P<0.05) and total bacteria (P<0.05) counts of the ileal digesta and the Bifidobacterium (P<0.05) and Lactobacillus counts of cecal digesta in piglets. Dietary LGG supplementation increased the Lactobacillus, LGG and total bacteria counts of the ileal digesta and the Lactobacillus, Bifidobacterium and LGG of the cecal digesta (P<0.05), decreased the pH of the ileal digesta and the Escherichia coli counts of the ileal and cecal digesta in piglets (P<0.05). Furthermore, dietary LGG supplementation could attenuate the effects of RV challenge on the pH and the Lactobacillus, total bacteria, Bifidobacterium and Escherichia coli counts of the ileal or cecal digesta in piglets.(7) RV challenge increased the malondialdehyde (MDA) concentration of the duodenum, jejunum, ileum and serum (P<0.05), decreased the total superoxide dismutase (T-SOD) activity of the jejunum and the glutathione peroxidase (GSH-Px) activity of the duodenum, jejunum, ileum and serum (P<0.05), and decreased the total antioxidant capacity (T-AOC) of the jejunum and serum in piglets (P<0.05). Dietary LGG supplementation decreased the MDA concentration of the jejunum (P<0.05), increased the T-SOD activitiy of the jejunum and the GSH-Px activitiy of the serum (P<0.05), and increased the T-AOC of the jejunum and serum in piglets (P<0.05). Dietary LGG supplementation could attenuate the effects of RV challenge on the MDA concentration, the T-SOD activity and the T-AOC of the jejunum or serum in piglets.In conclusion, these results suggest that RV challenge could induce a serious diarrhea, oxidative stress, intestine damage and immune dysfunction, which lead to the decline growth performance. However, dietary LGG supplementation improve the growth performance, and alleviated the diarrhea induced by RV challenge in piglets, which could be due that dietary LGG supplementation might improve immunologic function, antioxidant capacity and intestinal barrier function in piglets.