Oregano-based feed additive reduces Salmonella enterica serovar Enteritidis colonization in young broilers

Authors: Swaggerty, Christina; CABRERA, M - Nutrinae, Llc; SASIA, SANTIAGO - Nutrinae, Llc; CABRERA, GABRIEL - Nutrinae, Llc; Genovese, Kenneth; Byrd Ii, James; Kogut, Michael; CABRERA, RAFAEL - Nutrinae, Llc

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2025
Publication Date: 5/29/2025
Citation: Swaggerty, C.L., Cabrera, M.D., Sasia, S., Cabrera, G., Genovese, K.J., Byrd II, J.A., Kogut, M.H., Cabrera, R. 2025. Oregano-based feed additive reduces Salmonella enterica serovar Enteritidis colonization in young broilers. Poultry Science. 104(8). Article 105301. https://doi.org/10.1016/j.psj.2025.105301.
DOI: https://doi.org/10.1016/j.psj.2025.105301

Interpretive Summary: Poultry producers are looking for alternative products to replace antibiotics. As such, natural products including plant extracts, botanicals, or essential oils are being used more and more as antibiotic replacements, and in most cases, these products are added to the feed when chicks are placed for the grow-out phase. Salmonella is one of the leading causes of foodborne illness and poultry can be a source. The purpose of this study was to determine if feeding an antibiotic alternative made from oregano could reduce the numbers of Salmonella in chickens. Chicks were assigned to two groups. The first group was fed a control diet with no oregano while the second group was fed a diet with the oregano supplement. When the chicks were 7 days old, they were administered a dose of Salmonella. Two weeks later the study ended, and samples were collected from the chicks in the two groups. We found the chicks on the oregano diet were less likely to have Salmonella than those on the control diet. Additionally, of the birds that did have Salmonella, the ones on the oregano diet had significantly fewer numbers of Salmonella compared to those on the control diet. To determine what might be contributing to the Salmonella reduction, we measured various chemical messengers called cytokines and chemokines that are involved in the immune response. The samples collected from the chicks on the oregano diet had higher levels of three important cytokines and chemokines that are known to be associated with increased resistance to Salmonella indicating the oregano feed supplement boosted the immune response of the young chicks. The results from this study show that feeding a diet supplemented with an oregano feed additive reduces the number of Salmonella in the chicken. Reducing the number of Salmonella in the chicken at the farm reduces the chance of contamination during processing; thereby creating a safer and more wholesome product for consumers.

Technical Abstract: Salmonella is one of the leading bacterial foodborne pathogens and is commonly found in poultry. The objective of this study was to determine if feeding an oregano-based antibiotic alternative could reduce the burden of Salmonella in broilers. Day-of-hatch straight-run broiler chicks were provided a basal corn-soymeal diet. After four days on the basal diet, birds were assigned to a dietary treatment group (n=50 chicks/group/experiment). The groups were control with no oregano feed additive or a diet supplemented with an oregano product (300 g/ton). At 7-days-of-age, chicks were challenged via oral gavage (0.5 mL) with Salmonella enterica serovar Enteritidis (5x10^4) colony forming units [cfu]/chick). Eleven-days post-challenge (dpc), 50 birds from each group were humanely euthanized. At necropsy, the liver and one cecal pouch were removed and enriched for S. Enteritidis and cecal content was analyzed for S. Enteritidis enumeration. The study was conducted twice. Data were analyzed to determine differences in S. Enteritidis recovered between the groups with P<0.05 significant. No differences (P=0.27) were observed in the percent positive liver samples in the controls (21%) compared to those on the oregano diet (15%). There was a reduction (P=0.003) in the positive ceca between controls (61%) compared to chickens on the oregano diet (40%). The S. Enteritidis recovered from cecal content was also reduced (P<0.001) in chickens on the oregano diet (3.2 x 10^3 cfu/g) compared to controls (3.5x10^5 cfu/g). Cytokine (IL-1beta and IL-18) and chemokine (CXCL8) mRNA expression was also 1.9-2.2-fold higher (P<0.04) in the cecal tonsil of chickens on the oregano diet compared to controls indicating immunomodulatory affect. Collectively, these data demonstrate addition of an oregano-based feed additive to a broiler diet reduces S. Enteritidis colonization and invasion and may be an important pre-harvest intervention strategy to reduce the burden of this highly important foodborne pathogen.