Gut microbiome and serum metabolome analyses identify Bacteroides fragilis as regulators of serotonin content and PRL secretion in broody geese1

Abstract

Broody behavior is regulated by hypothalamic prolactin secretion, which seriously affects egg production in poulty production. Numerous studies have provided evidence that animal behavior is governed by dynamic bidirectional communication between specific gut bacteria and their host via the Brain-Gut-Microbiome Axis. However, little research focused on how the gut microbiota influence broody behavior in poultry. In this study, Zhedong white geese in laying and brooding phases were selected. Ten differentially abundant bacteria in cecum were detected between brooding and laying geese through metagenomic analyses and 16S rRNA sequencing (P < 0.05), and Bacteroides fragilis (B. fragilis) was specifically identified as a key driver species in the brooding geese. Moverover, the serum metabolites were quantified, and the 313 differentially abundant metabolites were found between the two different physiological geese. They were primarily enriched in the tryptophan metabolism pathways. Pearson correlation analyses revealed there was significant positive correlation between B. fragilis abundance and the context of 11 tryptophan metabolism-related metabolites (such as serotonin, et al.) in broody geese, which hinted that those the tryptophan metabolites might be produced or driven by B. fragilis. Finally, the serum hormone levels were also measured. We found there was a positive correlation between B. fragilis abundance and content of serotonin. Besides, prolactin secreted by the pituitary gland was greater in brooding geese than that in laying geese, which was also highly correlated with B. fragilis abundance. This result implied that B. fragilis could promote the secretion of prolactin by the pituitary gland. Together, the current study findings provided the information on gut microbiota influencing broody behavior, B. fragilis produced or driven more serum serotonin, and stimulated the pituitary gland to secret more prolactin, which potentially offered a new enlightenment for the intervention of broody behavior in poultry.