Oregano essential oil: a pre-harvest tool to reduce Salmonella enterica serovar Enteritidis in market-age broilers

Authors: Swaggerty, Christina; SASIA, SANTIAGO - Nutrinae, Llc; CABRERA, DOLORES - Nutrinae, Llc; Byrd Ii, James; Genovese, Kenneth; Anderson, Robin; CABRERA, GABRIEL - Nutrinae, Llc; CABRERA, RAFAEL - Nutrinae, Llc

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: The goal of this study was to test whether oregano essential oil (OEO) could help reduce the food poisoning bacteria Salmonella Enteritidis (SE) in broiler chickens before they are harvested. OEO is a natural product derived from the leaves and flowers of the oregano plant. Two similar experiments were run using 200 chicks that went from 0 to 43 days old. Each experiment included two pens with 50 chickens each. All birds were fed the same corn–soybean meal diet for the first four days, switching from starter to grower to finisher diets to meet their nutritional needs. On day 7, the chickens were given SE by mouth (about 100,000 to 1,000,000 bacteria per bird). At day 43, one cecal pouch from the gut of each bird was collected to check for SE, and the cecal contents were tested to measure SE levels using standard lab methods. Chickens that received OEO had lower SE infection rates—34% compared to 49% in the control group. SE numbers in the cecum were also about 10 times lower in the birds given OEO. OEO also reduced the production of certain proteins in the immune tissue of the gut linked to inflammation, called IL-21 and MIP-1ß. In short, adding OEO to feed and water lowered SE infection and bacterial load in broilers, likely by reducing inflammation in key immune tissues. This could help prevent the spread of SE within flocks and supports using OEO as a as a on-farm strategy to reduce SE in market-age chickens.

Technical Abstract: The objective of this study was to assess oregano essential oil (OEO) as a pre-harvest intervention to reduce Salmonella enterica serovar Enteritidis (SE) colonization in broilers. Two identical floor-pen trials were conducted with a total of 200 Ross 708 straight-run chicks (0 to 43 d). Each trial included 2 pens (50 chickens/pen). All chickens received a common basal corn–soybean meal (SBM) diet from 0 to 4 d of age and followed a phase-feeding program consisting of starter, grower, and finisher diets to match nutritional requirements.). At 7 d, chickens were challenged via oral gavage with SE (1 × 105–106 CFU/0.5 mL per chick). At 43 d, one cecal pouch per bird was collected for SE enrichment to determine prevalence, and cecal content was analyzed for SE load using standard microbiological procedures. Data were analyzed using Student’s t-test, with significance declared at P < 0.05. OEO supplementation reduced SE prevalence from 49% in the control to 34% (P = 0.03). Cecal SE counts were also reduced by approximately 1 log10 with OEO compared with the control (2.7 × 10³ vs. 1.9 × 10² CFU/g; P = 0.02). Mechanistically, OEO supplementation significantly (P ' 0.05) reduced protein expression of key inflammatory cytokine (IL-21) and chemokine (MIP-1') in the cecal tonsil compared to tissue from control-fed chickens. Therefore, OEO supplementation in the feed and water reduced SE prevalence and load in broilers, indicating greater resistance to colonization by reducing inflammation in important lymphoid tissue. This effect may potentially reduce flock-level transmission risk and supports OEO application as a pre-harvest strategy to reduce SE colonization in market-age broilers.