Incomplete degradation products of galactomannan from Sesbania cannabina modulated the cecal microbial community of laying hens.

Galactomannan and its degradation products have been gaining attention based on their possible means for improving the natural defense of the host through modulation of the bacterial population in the gut. Herein, incomplete degradation products of galactomannan (IDPG) was supplemented into the diet of aged laying hens to investigate the efficacy of IDPG on the gut microbiome. Four treatments with six replicates of twelve 68-wk-old laying hens (Hy-Line variety brown) each were fed a basal diet supplemented with 0%, 0.01%, 0.025%, and 0.05% IDPG for 8 wk. Results showed that the propionate concentration significantly increased in laying hens fed a diet supplemented with 0.025% or 0.05% IDPG relative to the control diet (P < 0.05). Moreover, the results of 16S rRNA gene sequencing revealed that there was a notable elevation of microbiome species diversity due to the addition of IDPG, with a noted enrichment to phyla Bacteroidetes at the expense of Firmicutes and Proteobacteria. Metabolic prediction of the cecal microbiome suggested significant improvements to carbohydrate and lipid metabolism and a significant depletion for energy metabolism and infectious diseases. More importantly, a strong positive correlation between levels of genera Bacteroides, Rikenellaceae_RC9_gut_group, and Prevotellaceae_UCG-001 with high production of propionate was found using multivariate analysis. Our study demonstrated that IDPG acted by mainly enriching the phyla Bacteroidetes in the cecum, increasing species diversity, and cecal propionate concentrations. It seems that IDPG can be used as feed additives in laying hen farming due to its capacity to positively modulate the cecal microbiome and aid improve overall health. The health and nutritional status of poultry are largely interconnected with the gut microbiome, which directly or indirectly affects gut morphology, nutrition, and immune responses. Dietary fiber is resistant to digestion in the small intestines of monogastric animals but is completely or partially fermented in the distal gut, thus it is understood that they could stimulate gut health. Incomplete degradation products of galactomannan (IDPG) is an important member of the dietary fiber family of molecules, however, there exists scant research on their beneficial effects on human or animal health. Our study demonstrated that IDPG acted by mainly enriching the phyla Bacteroidetes in the cecum, which are common bacteria in the gut that are involved in the fermentation of carbohydrates. Thereafter, the enriched phyla Bacteroidetes produced propionate and reduced the abundance of phyla Firmicutes and Proteobacteria by competitive inhibition. IDPG has also increased species diversity and enhanced the stability of intestinal flora, thereby exhibiting excellent prebiotic activity.

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