Dietary Fermented Blueberry Pomace Supplementation Improves Small Intestinal Barrier Function and Modulates Cecal Microbiota in Aged Laying Hens

This study aimed to investigate the effects of fermented blueberry pomace (FBP) on the intestinal barrier function and cecal microbiome of aged laying hens. A total of 320 Yukou Jingfen No. 8 laying hens (345-day-old) were randomly divided into a control group, 0.25% FBP group, 0.5% FBP group, or 1.0% FBP group. The results showed that the villus height (VH) in the jejunum of the 0.25-0.5% FBP groups and villus surface area in the jejunum of the 0.25% FBP group were higher (<i>p</i> < 0.05), while 0.25% FBP supplementation displayed a higher (<i>p</i> = 0.070) VH in the ileum compared to the control group. <i>Mucin-2</i> expression was upregulated (<i>p</i> < 0.05) in the jejunum of the 0.5% FBP group and the ileum of the 0.25-0.5% FBP groups. Compared to the control group, interleukin (<i>IL</i>)-4 and <i>IL-13</i> expressions were upregulated (<i>p</i> < 0.05) in the 1.0% FBP group. Microbiota analysis revealed that <i>Prevotella</i> abundance in the cecum of the 0.5-1.0% FBP groups was higher (<i>p</i> < 0.05) than in the 0.25% FBP group. In addition, microbial function prediction analysis showed that cecal microbiota in the 0.25% FBP group were mainly enriched by alanine/aspartate/glutamate metabolism and methane metabolism. Moreover, Spearman's correlation analysis revealed the potential correlations between the abundance of the cecal microbiota and intestinal-barrier-function-related gene expressions, as well as the short-chain fatty acid content, of laying hens. In summary, dietary FBP supplementation enhanced intestinal barrier function by improving intestinal morphology, upregulating gene expressions related to barrier function, and altering the cecal microbiota of aged laying hens.