Benzoic acid and oregano essential oil interact to increase the immune function and intestinal development of Langshan chickens

1. This study was conducted to investigate the effects of dietary supplementation with benzoic acid (BA) and oregano essential oil (OEO) on the growth, performance, immune function and intestinal development of Langshan chickens.2. A total of 240 Langshan chickens were randomly allocated into five treatment groups in a 42 d trial (aged 30-72 d): Basal diet (CON); basal +50 mg/kg chlortetracycline (CTC); basal +2,000 mg/kg BA (BA); basal +300 mg/kg OEO (OEO); basal +2,000 mg/kg BA and 300 mg/kg OEO (BA+OEO).3. Compared with CON the BA, OEO and BA+OEO groups elevated jejunal goblet cell numbers (<i>p</i> < 0.05) and lowered serum interleukins IL-1β, IL-6, IL-8 and TNF-α at both 51 and 72 d of age (<i>p</i> < 0.001). The BA+OEO group altered caecal microbiota beta-diversity (<i>p</i> < 0.001) and increased <i>Alistipes</i> and <i>Faecalibacterium</i> spp. abundance compared to CON and CTC (<i>p</i> < 0.05).4. These results suggested that supplementing BA with OEO gave better responses than chlortetracycline in enhancing immune responses and intestinal health.