Abstract
This study investigated the dynamic shifts in mucosa-associated microbiota composition and mucosal morphology in the colon of sheep fed a high grain (HG) diet. A total of 20 male sheep were randomly assigned to four groups (n = 5 for each). The sheep in first group received hay diet. The animals in other 3 groups were fed an HG diet for 7 (HG7), 14 (HG14), or 28 (HG28) days, respectively. Colonic digesta samples were collected to determine the pH and the concentrations of volatile fatty acid (VFA) and lactate. The colonic mucosa was sampled to characterize the bacterial communities using Illumina MiSeq sequencing and to determine mRNA expression levels of cytokines and tight junction protein genes using quantitative real-time PCR. As time advanced, results revealed that colonic pH linearly decreased (P = 0.007), and the concentrations of total VFA linearly increased (P < 0.001). Microbial analysis showed that an HG diet linearly reduced (P < 0.050) the diversity and richness of the colonic microbiota. The principal coordinate analysis results showed that the colonic mucosa-associated bacterial communities of the four groups significantly shifted with number of days fed an HG diet. At the genus level, HG feeding significantly increased the relative abundance of some taxa including Prevotella, Coprococcus, Roseburia, and Clostridium_sensu_stricto_1, and decreased the proportion of Treponema, and the percentage of these taxa was not affected by days fed an HG diet. The microscopic examination showed that HG feeding caused the mucosal epithelial injury. The RT-PCR results showed that the mRNA expression of claudin-1 (P = 0.038), IL-1β (P = 0.045), IL-6 (P = 0.050), and TNF-α (P = 0.020) increased linearly with number of days fed an HG diet. The correlation analysis revealed significant correlation between the colonic mucosal mRNA expression of cytokines and mucosal bacterial composition. Generally, HG feeding increased colonic fermentation and altered colonic mucosal bacterial communities, which eventually caused colonic mucosal damage and led to colonic dysfunction, and these changes occurred gradually over at least 4 weeks.
Highlights
In modern ruminant production systems, feeding high grain (HG) diets to high producing ruminant animals has become a common strategy for increasing milk yields and maximizing economic efficiency (Krause and Oetzel, 2005; Tufarelli and Laudadio, 2011; Gao and Oba, 2014)
Our results showed that the concentration of total volatile fatty acids (VFA) linearly increased with number of days fed an HG diet, which may contribute to the colonic mucosal injury
To the best of our knowledge, the present study is the first to survey the dynamic shifts of colonic mucosal microbiomes during HG feeding using high-throughput technology in sheep
Summary
In modern ruminant production systems, feeding high grain (HG) diets to high producing ruminant animals has become a common strategy for increasing milk yields and maximizing economic efficiency (Krause and Oetzel, 2005; Tufarelli and Laudadio, 2011; Gao and Oba, 2014). This feeding strategy poses a challenge for the epithelium and microbiota of the gastrointestinal (GI) tracts in these animals (Chen et al, 2011; Liu et al, 2013). The hindgut has no natural defense against acidosis and VFA toxicity, which may lead to an unhealthy GI environment, eventually leading to dramatic alterations in microbial compositions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
