Molecular responses to clove and oregano essential oils are associated with reduced inflammation and improved gut barrier function in broiler chickens

Authors: Park, Inkyung; Nam, Hyoyoun; RAVICHANDRAN, SRIPATHY - Avt Natural North America; WALL, EMMA - Avt Natural North America; Lillehoj, Hyun

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2024
Publication Date: 12/20/2024
Citation: Park, I.N., Nam, H., Ravichandran, S., Wall, E., Lillehoj, H.S. 2024. Molecular responses to clove and oregano essential oils are associated with reduced inflammation and improved gut barrier function in broiler chickens. Poultry Science. 104(2). Article e104713. https://doi.org/10.1016/j.psj.2024.104713.
DOI: https://doi.org/10.1016/j.psj.2024.104713

Interpretive Summary: Development of novel alternatives-to-antibiotics for poultry production is becoming a high priority with increasing regulation of growth promoting antibiotics in poultry production. During the last 10 years, many plant-derived chemicals that resist fungal, bacterial and viral infections (phytochemicals) have been shown to exert positive effects on gut health and production efficiency in animals. In this paper, ARS scientists in Beltsville, Maryland collaborated with scientists in the industry to identify plant-derived phytochemicals as non-antibiotic feed additives that can mitigate intestinal disease responses in broiler poultry. From in vitro screening of more than 20 plant-derived phytochemicals, two plant-derived phytochemicals, Clove essential oil (CEO) and Oregano essential oil (OEO), were selected. Further tests, to evaluate the ability of CEO and OEO to kill intestinal pathogens such as the Eimeria tenella parasite and Clostridium perfringens bacteria, and to assess their effects on host responses including inflammation, gut health, and muscle growth were conducted. The results of this study clearly demonstrated many beneficial effects of CEO and OEO as feed additives in poultry production to replace antibiotics and to mitigate two major intestinal infections, coccidiosis and necrotic enteritis. These findings indicate that both CEO and OEO are promising candidates as antibiotic alternatives in broiler chicken production.

Technical Abstract: In vitro tests were conducted to characterize the host-mediated responses of chickens to Clove Essential Oil (CEO) and Oregano Essential Oil (OEO). Chicken macrophage cells (CMCs), chicken intestinal epithelial cells (IECs), quail muscle cells (QMCs), and chicken embryonic muscle cells (EMCs) were utilized in these assays. EMCs were collected from the 13-day-old embryo during egg incubation and all cell lines were seeded at 2 × 105/mL in a 24-well plate. In CMCs, an inflammatory response was induced by stimulating with 1.0 µg/mL of Lipopolysaccharide (LPS). To induce muscle cell differentiation, 0.5% FBS was used in QMCs and 2.0% FBS in EMCs. Three different concentrations (1.0, 10.0, and 100 µg/mL) of CEO and OEO were administered. qRT-PCR was used to measure the gene expression levels of IL-1ß and IL-8 from CMCs, occludin, ZO-1, and MUC2 from IECs, and Pax7 and MyoG from QMCs and EMCs. Cytotoxic effects of CEO and OEO were determined using an MTT assay; CEO and OEO did not show cytotoxicity at concentrations below 0.1 mg/mL in CMCs, IECs, QMCs, and EMCs. CEO reduced (P < 0.05) the LPS-induced increase of IL-1ß and IL-8 in CMCs and increased (P < 0.05) ZO-1 and MUC2 in IECs. OEO suppressed (P < 0.05) the release of IL-8, increased ZO-1, and Pax7. Both CEO and OEO demonstrated bactericidal ability against sporozoite of E. tenella and C. perfringens bacteria, but only at doses 10-100× higher than those that would be used in feed. These findings support our previous findings on other phytochemicals; both CEO and OEO are promising non-antibiotic feed additive candidates for improved resilience in chickens not due to their antimicrobial effects, but due to gut molecular responses that take place at the level of the host.