Regulation of intestinal health by Lactobacillus rhamnosus GG during fasting-induced molting in laying hens

Abstract

This study aims to investigate the regulatory effects of adding Lactobacillus rhamnosus GG (LGG) during the fasting-induced molting (FIM) process on the intestinal mucosal barrier and microbiota of laying hens. A total of 288 houdan chickens of 420 days of age were randomly divided into four groups, with nine replicates in each group and each replicate containing eight chickens: NC group (no LGG added); TB group (LGG was added during the pre-fasting period (F0 period)); TF group (LGG was added during the fasting period (F15 period)); TBF group (LGG was added during both the pre-fasting and fasting periods). The FIM experiment focused on four key time points: F0, F15, the 5th day (R5), and the 30th day (R30) of refeeding. At each time point, one chicken was randomly selected from each replicate, euthanized via jugular vein exsanguination, and samples of the jejunum and ileum tissues, fixed samples, and cecal contents were collected for subsequent experiments. The results show that compared with the other three groups, the TBF group exhibited significant improvements in terms of egg production rate, egg quality, and changes in the ratio of villus height to crypt depth (V/C) in the jejunum and ileum. Compared with NC group, TBF group significantly increased the activity of antioxidant enzymes in serum during fasting, enhanced of the body's immune function, and also improved the intestinal barrier function, reduced intestinal inflammation and the content of oxidase, and further enhanced the digestion and absorption ability of FIM laying hens. The 16S sequencing results indicated that compared with the NC group, the TBF group significantly increased the abundance of beneficial bacteria during the refeeding period, reduced the number of pathogenic bacteria, optimized the intestinal microbiota structure, and promoted the production of short-chain fatty acids (SCFAs). In conclusion, the addition of LGG during the pre-FIM and fasting periods can improve the structure of the intestinal microbiota, promote the production of SCFAs, and improve intestinal barrier function, thereby enhancing intestinal health. This study provides a theoretical foundation and reference for the development of intestinal health and nutritional strategies for FIM laying hens.

Keywords: Fasting-induced molting; Intestinal health; Lactobacillus rahamnosus GG; Microbiota; Short-chain fatty acids.

Fig. 1

Effect of LGG on the production performance of laying hens during the FIM process. (A) Weight loss rate; (B) Recovery rate; (C) Egg production rate.

Fig. 2

Effect of LGG on the morphology of the jejunum and ileum in laying hens during the FIM process. (A) Representative images of hematoxylin and eosin staining of jejunal and ileal sections before fasting; (B) Representative images of hematoxylin and eosin staining of jejunal and ileal sections during fasting; (C) Representative images of hematoxylin and eosin staining of jejunal and ileal sections at the beginning of refeeding; (D) Representative images of hematoxylin and eosin staining of jejunal and ileal sections at the end of refeeding. Scale bar = 200 μm. Villus height and crypt depth in the jejunum and ileum of laying hens from different groups were quantified. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.

Fig. 3

Effect of LGG on oxidative and antioxidant levels in the jejunum of laying hens during the FIM process. (A) T-AOC; (B) SOD; (C) CAT; (D) GSH-PX; (E) MDA. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.

Fig. 4

Effect of LGG on serum immune parameters in laying hens during the FIM process. (A) IgA; (B) IgG; (C) IgM. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.

Fig. 5

Effects of LGG on inflammatory factors, tight junction proteins, and proliferation-apoptosis-related genes in laying hens during the FIM process. (A) Expression of inflammatory factors during the FIM process; (B) Expression of tight junction proteins during the FIM process; (C) Expression of genes related to proliferation and apoptosis during the FIM process. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.

Fig. 6

Effect of LGG on the cecal microbiota of laying hens during the FIM process. (A) Relative abundance of cecal microbiota at the phylum level; (B) Relative abundance of cecal microbiota at the genus level; (C) Relative abundance of beneficial and harmful bacteria at the genus level (top 3) in different groups; (D-G) Diversity and richness indices of cecal microbiota in each group. Principal coordinate analysis (PCoA) plot of the cecal microbiota composition at the operational taxonomic unit (OTU) level from different groups. (H) Points with different colors represent the centroids of each group. The closer the points, the more similar the gut microbiota structure; (I) Differences in the relative abundance of cecal microbiota at the genus level between groups at different time points. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.

Fig. 7

Effect of LGG on cecal SCFAs in laying hens during the FIM process. (A) Acetate; (B) Propionate; (C) Butyrate; (D) Valerate; (E) Isobutyrate; (F) Isovalerate. Data are mean ± SEM. “*” means P < 0.05, “**” means P < 0.01, “***” means P < 0.001.