Yeast Culture Modulates Colonic Microbiota and Immune Barrier to Mitigate High-Concentrate Diet–Induced Stress in Sheep

Objective: To investigate the effects of yeast extract on colonic damage in sheep caused by high-concentrate diets, providing a theoretical basis for developing more precise probiotic formulations.Methods:This study selected 45 three-month-old Du Han F1 sheep of similar body condition and randomly divided them into three groups: a control group (CON) fed a standard diet, a high-concentrate diet (HC) group, and a yeast culture treatment group. A 15-day pretrial period was followed by a 60-day main trial. Following the feeding trial, colonic contents and colonic tissue samples were collected.Results: Indicate that feeding a high-concentrate diet caused damage to both the colonic mucosa and muscularis layers. Compared with the control group (CON), the high-concentrate diet (HC) group presented 29 DEGs. Following the addition of yeast culture (YC), the number of differentially expressed genes increased to 683, among which 6 were YC-specific genes. Eight differentially abundant bacterial genera were identified: increased abundance of [Eubacterium]-xylanophilum-group, Alistipes, Gastranaerophilales, Lachnospiraceae-UCG-010, and Cyanobacteria; decreased abundance of Ruminococcaceae;uncultured, Akkermansia, and Verrucomicrobiota. Concurrently, VFA levels decreased while ammonia nitrogen levels increased, accompanied by abnormal expression of host immune barrier-related genes (e.g., CLDN1, CXCL8). In the HCY group, colonic mucosal integrity improved, microbial composition underwent significant changes, VFA levels rebounded, and ammonia nitrogen levels decreased.Conclusions: This indicates that YC modulates the “microbiota-VFA-host” axis network to a certain extent.