Effective Control of Salmonella Enteritidis in Poultry by Dietary Supplementation with Microencapsulated Essential Oils

Abstract

Background/Objectives: Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) is a major pathogen associated with poultry products, and the rise of antimicrobial-resistant strains has intensified the need for effective natural control strategies. Essential oils (EOs) are recognized for their antimicrobial potential, but their volatility, instability, and risk of toxicity at high concentrations limit their practical application. Therefore, the objective of this study was to evaluate the antimicrobial efficacy of EOs in broilers infected with S. Enteritidis and to characterize potential synergistic or antagonistic interactions between the oils. Methods: To achieve this, the oils were first assessed through Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), and Fractional Inhibitory Concentration (FIC) assays, and the most effective ones against S. Enteritidis were selected. These selected oils were then microencapsulated and incorporated into the broiler feed for the in vivo assay. Results: The encapsulated formulation retained key bioactive compounds and significantly reduced bacterial shedding and intestinal colonization when administered to broilers experimentally infected with S. Enteritidis. Broilers receiving the optimized half-dose supplementation exhibited a 36% reduction in fecal shedding and a 4 log₁₀ decrease in cecal bacterial counts compared to untreated controls. A transient reduction in liver colonization was also observed, while feed intake remained unaffected. Conclusions: These findings demonstrate that microencapsulated EOs can serve as an effective natural strategy to control S. Enteritidis in poultry. The results support the broader application of lipid-based encapsulation technologies for improving the functional performance of phytobiotics in animal production.

Keywords: cinnamon; clove; oregano; phytobiotics; poultry farm; synergistic effect.

Figure 1

(A) HPLC retention profiles of analytical markers: cinnamaldehyde, eugenol, carvacrol, and thymol. (B) Chromatographic profile of the encapsulated EO blend analyzed using HPLC. Detection performed at 203 nm; major peaks correspond to retained active compounds within the lipid matrix.

Figure 2

Fecal shedding of S. Enteritidis during 21 days of the experiment. Groups A (half dose of EO blend), B (full dose of EO blend), and C (non-treatment). A = 54.44% positive swabs for S. Enteritidis; B = 77.77%; C = 90%. **** High statistical difference between groups A/B and A/C.

Figure 3

The viable CFU/g of cecal contents from chickens inoculated with S. Enteritidis (SE P125 109): (I); spleen (II); and liver (III). Group A (half dose of EO blend), group B (full dose of EO blend), and group C (non-treatment). * (p < 0.05); ** (p < 0.01); Statistical difference in comparison between groups A, B, and C using two-way ANOVA with Bonferroni’s Multiple Comparisons test at 5% probability.

Figure 4

Average daily feed intake of broilers of groups A (half dose of EO blend), B (full dose of EO blend) and C (non-treatment).

Figure 5

Method of the Checkboard assay. MHB = Mueller–Hinton Broth; MIC = minimum inhibitory concentration. This figure was created using Biorender.com.