Effects of Encapsulated Mixtures of Plant Essential Oils and Organic Acids as an Alternative to Antibiotic Growth Promoters on Humoral Immune Response and Expression of Interleukin-4 and Interferon-Gamma Genes in Broilers

The poultry industry has achieved remarkable advancements in growth rates over the decades, primarily through antibiotic growth promoters (AGPs). Despite the benefits of AGPs, their use has sparked serious concerns regarding the rise of antibiotic-resistant bacteria, potential residues in animal products, and their broader implications for human health. These challenges have prompted increased regulatory scrutiny and a shift toward alternative strategies, such as nutrition, for maintaining poultry health and productivity. Therefore, this study evaluated the effect of an encapsulated mixture of essential oils and organic acids as an alternative to AGPs on humoral immunity, lymphoid organs, interleukin-4, and Interferon-gamma gene expression. A total number of 270 one-day-old male Ross-308 were assigned to three groups: control diet, control diet plus flavophospholipol (600 mg/kg), or control diet plus an encapsulated mixture of essential oils and organic acids (KaroGut™; 1L/1000L in drinking water). Humoral immunity was assessed via antibody titers against sheep red blood cells (SRBC) and Newcastle Disease Virus (NDV). The weight of Fabricius and the spleen's bursa and the expression of IL-4 and IFN-γ in the jejunum were measured. Results showed that birds supplemented with essential oils and organic acids increased anti-SRBC and NDV antibody titers vs control (p<0.05). The relative weights of the bursa of Fabricius and the spleen as key lymphoid organs tended to be higher for essential oils and organic acids. IL-4 and IFN-γ expression in the jejunum were significantly higher in birds supplemented with essential oils and organic acids vs control (p<0.05). These findings suggest that an encapsulated mixture of essential oils and organic acids could enhance immunity and related key gene expression, offering a viable alternative to AGPs in broilers.