Effect of dietary supplementation of organic acids and essential oils on immune function and intestinal characteristics of experimentally infected rabbits.

To analyze the effect of dietary organic acids and essential oils supplementation 120 young rabbits (28 d old) were divided into three groups and submitted to the following dietary treatments: Control diet; Zinc Bacitracin diet (Control diet+150 ppm Zinc Bacitracine); FormaXol diet (Control diet+0.4% FormaXol mixture of microincapsulated formic and citric acids and essential oils). At 38 d of age, all rabbits were experimentally infected with Escherichia coli O103 and Clostridium perfringens type A and clinically monitored for 3 weeks. To evaluate the native serum immunity (lysozyme, haemolytic complement assay and serum bactericidal activity) haematic samples were collected by cardiac puncture at regular intervals. Twenty one days after infection, all rabbits were euthanized and intestinal swabs were collected from different tracts of the small intestine, colon and caecum to investigate the aerobic and anaerobic bacteria. A jejune portion was excised to analyze the height of the villi. The haemolytic complement values showed a drastic reduction after infection in Control and Zinc Bacitracine diet animals; on the contrary, animals of FormaXol diet showed a steady trend in the first period (9 d) and a drastic reduction in the final period (11 d) like the others group. The better immune response in animals of FormaXol diet could be lied to higher values of serum bactericidal activity and lower values of lysozyme. The Control diet showed higher increase of lysozyme values after infection. All the studied immune parameters are in homeostatic equilibrium being subject to opposite phenomenon as production and consume. A similar percentage of E. coli O103 and C. perfringens type A were found in the Zinc Bacitracin and FormaXol groups. The highest percentage of non-pathogen bacteria was found in the Zinc Bacitracin and FormaXol rabbits. The results obtained measuring the villi height confirmed the previous analyses with a better value when FormaXol diet was used (P<0.05). Considered together these results show that 0.4% integration of microincapsulated formic acid and citric acids and essential oils reduces the damage of both Gram and Gram pathogen bacteria permitting to obtain a better serum innate response in experimentally infected rabbits.