The effect of gut microbiota-derived carnosine on mucosal integrity and immunity in broiler chickens challenged with Eimeria maxima

Authors: Park, Inkyung; NAM, HYOYOUN - US Department Of Agriculture (USDA); LEE, YOUNGSUB - US Department Of Agriculture (USDA); WICKRAMASURIYA, SAMIRU - US Department Of Agriculture (USDA); SMITH, ALEXANDRA - Arm & Hammer Animal And Food Production; REHBERGER, THOMAS - Arm & Hammer Animal And Food Production; Lillehoj, Hyun

Submitted to: Poultry Science
Publication Type: Pre-print Publication
Publication Acceptance Date: 5/4/2024
Publication Date: 8/1/2024
Citation: Park, I.N., Nam, H., Lee, Y., Wickramasuriya, S.S., Smith, A.H., Rehberger, T.G., Lillehoj, H.S. 2024. The effect of gut microbiota-derived carnosine on mucosal integrity and immunity in broiler chickens challenged with Eimeria maxima. Poultry Science. VOL.103/103837. https://doi.org/10.1016/j.psj.2024.103837.
DOI: https://doi.org/10.1016/j.psj.2024.103837

Interpretive Summary: In the post-antibiotic era, developing novel non-antibiotic feed additives has become increasingly important for controlling poultry diseases. In this paper, we describe a novel approach using metabolites as a non-antibiotic feed additive which exerts beneficial effects on growth performance and gut health. In our previous study, we have discovered beneficial effects of dietary supplementation of young broiler chickens with two selected strains of Bacillus subtilis that enhanced intestinal immune responses, epithelial barrier integrity, and growth performance after infection with coccidiosis. Detailed metabolomics study on the ileum of chickens fed with combination of Bacillus subtilis 1781 and 747 led to the identification of carnosine whose expression was increased. Carnosine, a dipeptide consisting of ß-alanine and histidine, is widely distributed in various tissues of animals, and its presence in the intestine suggests potential roles in intestinal health and gut functions. This study showed that carnosine exhibits anti-inflammatory and antioxidant properties, improves the integrity of the intestinal barrier, and modulates host immune system in chickens. The results of this study provide valuable insights into the mechanisms underlying the beneficial physiological changes associated with dietary feeding of young poultry with an intestinal metabolite such as Carnosine which is generated by feeding Bacillus subtilis direct-fed microbes.

Technical Abstract: In the first study, an in vitro culture system was developed to investigate the effects of carnosine on macrophage proinflammatory cytokine response using an established chicken macrophage cell line (CMC), gut integrity using a chicken intestinal epithelial cell line (IEC), muscle differentiation in quail muscle cells (QMCs) and primary chicken embryonic muscle cells (PMCs), and direct anti-parasitic effect against E. maxima sporozoites. Cells to be tested were seeded in 24-well plates and treated with carnosine at 4 different concentrations (0.1, 1.0, and 10.0 µg). After 18 h of incubation, cells were harvested to measure gene expression of proinflammatory cytokines in CMC, tight junction (TJ) proteins in IECs, and muscle cell growth markers in QMCs and PMCs. In vivo trials were conducted to investigate the effect of dietary carnosine on disease parameters in broiler chickens challenged with E. maxima. One hundred and twenty male broiler chickens (0-day-old) were allocated into four treatment groups: (1) basal diet without infection (NC), (2) basal diet with E. maxima infection (PC), (3) carnosine at 10.0 mg/kg feed with PC (HCS), and (4) carnosine at 1.0 mg/kg feed with PC (LCS). All groups except NC were orally infected with E. maxima on day 14. Jejunal samples were collected for lesion scoring and jejunum gut tissues were used to conduct transcriptomic analysis of cytokines and TJ proteins. In vitro, carnosine treatment significantly decreased IL-1ß gene expression in CMC following LPS stimulation. In vivo feeding studies showed that dietary carnosine increased BW and ADG of chickens in E. maxima-infected groups and reduced jejunal lesion score and fecal oocyst shedding in HCS group. Jejunal IL-1ß, IL-8, and IFN-gamma expression were suppressed in the HCS group compared to PC. The expression levels of claudin-1 and occludin in IECs were also increased in HCS following carnosine treatment. In conclusion, these findings highlight the beneficial effects of dietary carnosine supplementation on intestinal immune responses and gut barrier function in broiler chickens exposed to E. maxima challenge infection. Key words: antibiotic alternative feed additives, growth promotion, gut health, gut metabolite, carnosine, in vitro test.