Effects of dietary maltol on innate immunity, gut health and growth performance of broiler chicken challenged with Eimeria maxima

Authors: PARK, INKYUN - US Department Of Agriculture (USDA); GOO, DOYUN - US Department Of Agriculture (USDA); NAM, HYOYOUN - US Department Of Agriculture (USDA); WICKRAMASURIYA, SAMIRU - US Department Of Agriculture (USDA); LEE, KICHOON - The Ohio State University; ZIMMERMAN, NOAH - Arm & Hammer Animal And Food Production; SMITH, ALEXANDRA - Arm & Hammer Animal And Food Production; REHBERGER, THOMAS - Arm & Hammer Animal And Food Production; Lillehoj, Hyun

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2021
Publication Date: 5/20/2021
Citation: Park, I., Goo, D., Nam, H., Wickramasuriya, S., Lee, K., Zimmerman, N.P., Smith, A.H., Rehberger, T.G., Lillehoj, H.S. 2021. Effects of dietary maltol on innate immunity, gut health and growth performance of broiler chicken challenged with Eimeria maxima. Frontiers in Veterinary Science. https://doi.org/10.3389/fvets.2021.667425.
DOI: https://doi.org/10.3389/fvets.2021.667425

Interpretive Summary: Development of alternative strategies to eliminate the use of harmful antibiotics is a priority for the animal agriculture. In this paper, ARS scientists collaborated with scientists at Arm & Hammer company to find an alternative strategy that can promote health of animals using metabolites as feed additives since some of metabolites exert a positive influence on the host health. Based on our earlier study that showed beneficial effects of dietary Bacillus subtilis on host immunity, we chose maltol as an example of metabolites to investigate its effects on immunity and other physiological functions. The results of in vitro cell culture and in vivo studies demonstrated that maltol can improve the growth performance, intestinal immune response, and gut barrier integrity of chickens when chickens are infected with E. maxima in vivo. These results demonstrate the beneficial effects of dietary maltol in host response to disease and the need to study the mode of action of maltol in host response to parasitic and other enteric diseases.

Technical Abstract: Two studies were conducted to evaluate the effects of maltol on innate immunity, gut health, and enteric infection. In the first study, an in vitro culture system was used to evaluate the effects of maltol on the innate immune response of chicken macrophage cells (CMC), gut integrity of chicken intestinal epithelial cells (IEC), anticoccidial ability against E. maxima, and differentiation of quail muscle cells (QMC) and primary chicken embryonic muscle cells (PMC). In the second in vivo study, the dietary effect of maltol on disease parameters, including growth performance, gut lesion, epithelial cell integrity, fecal oocyst shedding, and host immune response, after oral infection with E. maxima was evaluated by feeding high and low doses to newly hatched commercial broiler chickens, to determine the applicability of maltol as a postbiotic. For the in vivo evaluation of the effects of dietary maltol on enteric infection, 80 male one-day-old broiler chickens were allocated into the following four treatment groups: 1) control (CON: basal diet without infection), 2) negative control (NC: basal diet with E. maxima infection), 3) high-maltol diet (HI: 10.0 mg/kg feed), and 4) low-maltol diet (LO: 1.0 mg/kg feed). Body weight (BW) and average daily weight gain measurements were performed on days 0, 7, 14, 20, and 22 after all chickens, except for those in the CON group, were orally infected with 104 E. maxima oocysts per chicken on day 14. Fecal samples were collected from chickens 6 to 8 days post-infection, and jejunum samples were used to score gut lesions and conduct gene expression analysis for estimation of cytokine and TJ protein levels. Growth performance was analyzed using PROC MIXED in SAS, and treatments were compared in a pairwise manner using the PDIFF option. In vitro, maltol increased (P < 0.001) the gene expression levels of occludin (1.0- to 2.5-fold), ZO-1 (1.0- to 2.6-fold), and MUC2 (1.0- to 2.5-fold) in IEC compared to that in the CON group and increased (P < 0.001) IL-1ß (1.7- to 28-fold) and IL-8 (2.8- to 236-fold) levels in the LPS-stimulated CMC compared to that in the non-LPS groups, regardless of the dose administered. In conclusion, dietary maltol improved the immune responses of IEC and CMC in vitro, and improved the growth performance, intestinal immune response, and gut barrier integrity of chickens infected with E. maxima in vivo. These results demonstrate the beneficial effects of dietary maltol in the enhancement of growth performance, gut health, and disease resistance in coccidiosis and the applicability of maltol as a postbiotic for the replacement of antibiotic growth promoters in commercial poultry production.