Dietary oregano essential oil supplementation improves intestinal barrier function and modulates the cecal microbiota and metabolites of beef cattle

The health of the hindgut in beef cattle plays a crucial role in their growth and overall health. Oregano essential oil (OEO) has gained attention as a potential alternative to antibiotics due to its various beneficial properties such as antibacterial and anti-inflammatory effects. However, its specific impacts on cecal health in beef cattle and its underlying mechanisms are yet to be fully understood. This study aimed to investigate the effects of OEO supplementation on basal immune status, intestinal barrier integrity-related gene expression, microbiota, and their metabolites in the cecum of beef cattle, thus to better understand its potential mechanism. Twenty-seven steers (initial body weigh 270.47 ± 16.26 kg) were randomly assigned to three groups with nine replicates each in a 390-day trial. Steers were fed with basal diet (CON), basal diet supplemented with 130 mg/d OEO (LOE), and basal diet with 260 mg/d OEO (HOE). Results showed that dietary HOE supplementation significantly increased the growth performance (average daily gain and final body weight) (P < 0.05). Compared to CON group, both LOE and HOE groups showed reduced levels of interleukin (IL)-1β, IL-2, and tumor necrosis factor α (TNF-α) (P < 0.05), while only HOE decreased IL-6 and increased IL-4 (P < 0.05). Moreover, HOE supplementation upregulated the intestinal tight junction proteins (ZO-1 and Claudin-1) gene expression (P < 0.05). The HOE group exhibited a significant increase in the relative abundances of cecal beneficial bacteria (e.g., Bacillus, Lactobacillus, and Lactococcus, P < 0.05). Furthermore, HOE supplementation increased the concentrations of butyrate in cecal short-chain fatty acids (P < 0.05). HOE supplementation has the potential to regulate cecal barrier homeostasis, the microbiota and its derived metabolites, improve basal immune status, and ultimately benefit the health and performance of steers.