Maternal IgY Accelerates <i>Lactobacillus</i> Colonization, Improves Intestinal Barrier Function and <i>Salmonella pullorum</i> Resistance of Offspring Chicks

The study was aimed at examining the effect of maternal IgY levels on embryonic development, gut microbiota colonization, and resistance to Salmonella pullorum infection in offspring chicks. A total of 60 thirty-six-week-old breeders that were sorted from 969 breeders according to their yolk IgY content were allocated to two groups: a high egg yolk IgY levels group (HIgY) and a low egg yolk IgY levels group (LIgY). Fertilized eggs of breeders were collected for hatching. On Day 8, offspring chicks were challenged with S. pullorum. Results showed that compared with the LIgY group, the HIgY group exhibited a considerable increase in embryonic weight, significant enhancement in the richness and diversity of gut microbiota, along with an increased relative abundance of Lactobacillus in 7-day-old chicks (p < 0.05). The bacterial load in the spleen, liver tissue, and cecal contents, the mRNA expression of nitric oxide synthase 2 (NOS2) and interleukin-1β (IL-1β) in the cecal tonsils and spleen of offspring chicks in the HIgY group markedly reduced on 1-day post-infection (dpi) compared with the LIgY group (p < 0.05), and mucin-2 (MUC2) and Occludin mRNA expression in the jejunum of offspring chicks in the HIgY group was markedly increased compared with the LIgY group (p < 0.05). In summary, maternal IgY increased the richness and diversity of gut microbiota, enhanced the colonization of Lactobacillus, improved the immunity and intestinal barrier function, thereby increasing the resistance against S. pullorum infection.