Probiotics are a nutritional tool for disease prevention. It has been proposed that stimulation of immune response could affect the growth-promoting properties of antimicrobial growth promoters as well as the control of foodborne pathogens. The current study compares immune response in the blood of 280 non-infected and Salmonella-infected chickens fed either with the growth promoter avilamycin or with one of five probiotic strains of Lactobacillus and Bifidobacterium, which also showed growth-promoting properties. All of the probiotic strains stimulated superoxide anion production and the proliferation of leukocytes, while raising lysozyme and γ-globulin levels (by up to 65%, p < 0.01), which are important factors in native and cell-mediated immune defense against pathogens. In contrast, among the two strains examined, specific Salmonella antibodies were induced only by L. salivarius, and not by B. animalis, as assessed by the ELISA method and confirmed by an agglutination reaction (p < 0.05). In the avilamycin-fed group, both non-infected and infected chickens showed decreased levels of these immune markers (by 30%) and increased levels of ceruloplasmin by up to 35%. In contrast, the probiotics suppressed acute-phase response assessed by ceruloplasmin by up to 32%. This correlation implies that various antimicrobial feed additives have a distinct effect on immunomodulation, which may affect different mechanisms in the nutrition-related metabolism associated with the rate of weight gain in chickens. The data could contribute to the design of innovative antimicrobial feed additives in the food industry and consequently to well-being of humans.
Keywords: Antimicrobial feed additives; Non-specific immunity; Poultry; Probiotics; Salmonella.