{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T21:11:21Z","timestamp":1790975481244,"version":"4.1.0"},"reference-count":56,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,11,11]],"date-time":"2025-11-11T00:00:00Z","timestamp":1762819200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007129","name":"Shandong Provincial Natural Science Foundation","doi-asserted-by":"publisher","award":["ZR2024QC376"],"award-info":[{"award-number":["ZR2024QC376"]}],"id":[{"id":"10.13039\/501100007129","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Agricultural Science and Technology Innovation Project of Shandong Academy of Agricultural Sciences","award":["CXGC2025F10"],"award-info":[{"award-number":["CXGC2025F10"]}]},{"name":"Agricultural Science and Technology Innovation Project of Shandong Academy of Agricultural Sciences","award":["CXGC2025B03"],"award-info":[{"award-number":["CXGC2025B03"]}]},{"name":"Jinan Introductory Innovation Team Project","award":["202228037"],"award-info":[{"award-number":["202228037"]}]},{"name":"Taishan Industry Experts Program","award":["TSCX202306046"],"award-info":[{"award-number":["TSCX202306046"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Metabolites"],"abstract":"<jats:p>Background: Tryptophan (Trp) is a limiting amino acid in poultry nutrition. Dietary supplementation of Trp not only enhances production performance, but also supports intestinal barrier integrity, alleviates stress, and boosts immunity, in which the derivatives from gut Trp-metabolizing commensal microbes play crucial roles. However, research on how excessive Trp affects poultry growth, metabolism, and gut microbiota composition remains limited. Methods: In this study, we investigated the effects of varying Trp levels (0.23%, 0.29%, 0.35%) on broiler production performance, immune function, and antioxidant levels through controlled feeding trials. These host responses were further correlated with cecal microbiota metagenomic sequencing data using multivariate analysis. Results: Compared with the basal 0.23% Trp level, a 0.35% of Trp addition significantly impaired broiler body weight gain and feed intake, and 0.29% Trp could increase thymus index and serum superoxide dismutase (SOD) level without affecting the growth performance; neither of these two levels affected the feed conversion rate. The cecal microbial metagenomic data further revealed that Trp supplementation reduced the abundance of harmful bacteria, while increasing the abundance of beneficial bacteria and Trp-metabolizing microorganisms. Correlation analysis showed that Trp supplementation was negatively correlated with body weight (BW) but positively correlated with thymus index and SOD level, with similar trends observed between the abundance of specific Trp-utilizing microorganisms and these indicators. Functional analysis revealed an increase in the abundance of KEGG orthology (KO) related to Trp metabolism from the aforementioned microbes. Conclusions: An appropriate addition of Trp (0.29%) can enhance certain metabolic levels without affecting production performance, which might be achieved through relevant metabolic pathways of intestinal microorganisms.<\/jats:p>","DOI":"10.3390\/metabo15110736","type":"journal-article","created":{"date-parts":[[2025,11,11]],"date-time":"2025-11-11T12:44:55Z","timestamp":1762865095000},"page":"736","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Effect of Tryptophan Supplementation Levels on the Cecal Microbial Composition, Growth Performance, Immune Function and Antioxidant Capacity in Broilers"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4648-1615","authenticated-orcid":false,"given":"Xuelan","family":"Liu","sequence":"first","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chunyan","family":"Fu","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qingtao","family":"Gao","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Heng","family":"Zhang","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2978-2571","authenticated-orcid":false,"given":"Tianhong","family":"Shi","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guiming","family":"Li","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"},{"name":"Shandong Lanhai Ecological Agriculture Co., Ltd., Dongying 257100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yunchao","family":"Wang","sequence":"additional","affiliation":[{"name":"Shandong Lanhai Ecological Agriculture Co., Ltd., Dongying 257100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-2683-4817","authenticated-orcid":false,"given":"Yan","family":"Shang","sequence":"additional","affiliation":[{"name":"Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China"},{"name":"Jinan Key Laboratory of Poultry Germplasm Resources Innovation and Healthy Breeding, Jinan 250100, China"},{"name":"Shandong Provincial Key Laboratory of Livestock and Poultry Breeding, Jinan 250100, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"54","DOI":"10.3382\/japr\/pfv061","article-title":"Apparent ileal digestible tryptophan requirements of 22- to 42-day-old broiler chicks","volume":"25","author":"Wang","year":"2016","journal-title":"J. Appl. Poult. Res."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1146","DOI":"10.1111\/jpn.13515","article-title":"Tryptophan in poultry nutrition: Impacts and mechanisms of action","volume":"105","author":"Fouad","year":"2021","journal-title":"J. Anim. Physiol. Anim. Nutr."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"226","DOI":"10.1093\/ps\/84.2.226","article-title":"Dietary tryptophan need of broiler males from forty-two to fifty-six days of age","volume":"84","author":"Corzo","year":"2005","journal-title":"Poult. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1080\/1828051X.2017.1340814","article-title":"Gut microbiota and transportation stress response affected by tryptophan supplementation in broiler chickens","volume":"17","author":"Bello","year":"2018","journal-title":"Ital. J. Anim. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1894","DOI":"10.3382\/ps\/pev155","article-title":"Effects of tryptophan supplementation on growth performance, antioxidative activity, and meat quality of ducks under high stocking density","volume":"94","author":"Liu","year":"2015","journal-title":"Poult. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1227","DOI":"10.1007\/s00726-017-2424-3","article-title":"Effects of dietary L-tryptophan supplementation on intestinal response to chronic unpredictable stress in broilers","volume":"49","author":"Yue","year":"2017","journal-title":"Amino Acids"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1007\/s00726-016-2351-8","article-title":"A review of the immunomodulatory role of dietary tryptophan in livestock and poultry","volume":"49","author":"Bai","year":"2017","journal-title":"Amino Acids"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1195","DOI":"10.1007\/s00726-010-0752-7","article-title":"Tryptophan metabolism, from nutrition to potential therapeutic applications","volume":"41","author":"Otten","year":"2011","journal-title":"Amino Acids"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Birkl, P., Chow, J., McBride, P., Kjaer, J.B., Kunze, W., Forsythe, P., and Harlander-Matauschek, A. (2019). Effects of acute tryptophan depletion on repetitive behavior in laying hens. Front. Vet. Sci., 6.","DOI":"10.3389\/fvets.2019.00230"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.bbr.2014.07.027","article-title":"Serotonin, tryptophan metabolism and the brain-gut-microbiome axis","volume":"277","author":"Clarke","year":"2015","journal-title":"Behav. Brain Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"473","DOI":"10.1038\/nrgastro.2013.105","article-title":"Serotonin signalling in the gut--functions, dysfunctions and therapeutic targets","volume":"10","author":"Mawe","year":"2013","journal-title":"Nat. Rev. Gastroenterol. Hepatol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"164","DOI":"10.1016\/j.jpsychires.2008.03.009","article-title":"The probiotic Bifidobacteria infantis: An assessment of potential antidepressant properties in the rat","volume":"43","author":"Desbonnet","year":"2008","journal-title":"J. Psychiatr. Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1079\/BJN19830068","article-title":"Effects of a dietary excess of leucine on the metabolism of tryptophan in the rat: A mechanism for the pellagragenic action of leucine","volume":"50","author":"Bender","year":"1983","journal-title":"Br. J. Nutr."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"641","DOI":"10.1111\/jnc.14709","article-title":"Increasing carbohydrate availability in the hindgut promotes hypothalamic neurotransmitter synthesis: Aromatic amino acids linking the microbiota-brain axis","volume":"149","author":"Gao","year":"2019","journal-title":"J. Neurochem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"795","DOI":"10.3136\/fstr.18.795","article-title":"The function of lactic acid bacteria on biogenic amines production by food-borne pathogens in arginine decarboxylase broth","volume":"18","author":"Kuley","year":"2012","journal-title":"Food Sci. Technol. Res."},{"key":"ref_16","first-page":"550","article-title":"Amine neuromediators, their precursors, and oxidation products in the culture of Escherichia coli K-12","volume":"45","author":"Shishov","year":"2009","journal-title":"Prikl. Biokhim. Mikrobiol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1007\/s00217-004-0988-0","article-title":"Production of biogenic amines by Morganella morganii, Klebsiella pneumoniae and Hafnia alvei using a rapid HPLC method","volume":"219","year":"2004","journal-title":"Eur. Food Res. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1016\/j.coi.2020.12.001","article-title":"Tryptophan and indole metabolism in immune regulation","volume":"70","author":"Fiore","year":"2021","journal-title":"Curr. Opin. Immunol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"716","DOI":"10.1016\/j.chom.2018.05.003","article-title":"Gut microbiota regulation of tryptophan metabolism in health and disease","volume":"23","author":"Agus","year":"2018","journal-title":"Cell Host Microbe"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Su, X., Gao, Y., and Yang, R. (2022). Gut microbiota-derived tryptophan metabolites maintain gut and systemic homeostasis. Cells, 11.","DOI":"10.3390\/cells11152296"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1038\/mp.2012.77","article-title":"The microbiome-gut-brain axis during early life regulates the hippocampal serotonergic system in a sex-dependent manner","volume":"18","author":"Clarke","year":"2013","journal-title":"Mol. Psychiatry"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1073\/pnas.0906112107","article-title":"The bacterial signal indole increases epithelial-cell tight-junction resistance and attenuates indicators of inflammation","volume":"107","author":"Bansal","year":"2010","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"19376","DOI":"10.1073\/pnas.2000047117","article-title":"Microbial tryptophan metabolites regulate gut barrier function via the aryl hydrocarbon receptor","volume":"117","author":"Scott","year":"2020","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Shimada, Y., Kinoshita, M., Harada, K., Mizutani, M., Masahata, K., Kayama, H., and Takeda, K. (2013). Commensal bacteria-dependent indole production enhances epithelial barrier function in the colon. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0080604"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Gao, J., Xu, K., Liu, H., Liu, G., Bai, M., Peng, C., Li, T., and Yin, Y. (2018). Impact of the gut microbiota on intestinal immunity mediated by tryptophan metabolism. Front. Cell. Infect. Microbiol., 8.","DOI":"10.3389\/fcimb.2018.00013"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Li, S. (2023). Modulation of immunity by tryptophan microbial metabolites. Front. Nutr., 10.","DOI":"10.3389\/fnut.2023.1209613"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1174","DOI":"10.3382\/ps.0671174","article-title":"Estimation of the tryptophan requirement of male broiler chickens","volume":"67","author":"Smith","year":"1988","journal-title":"Poult. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1002\/vms3.195","article-title":"Effect of dietary tryptophan supplementation on growth performance, immune response and anti-oxidant status of broiler chickens from 7 to 21 days","volume":"6","author":"Mund","year":"2020","journal-title":"Vet. Med. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4504","DOI":"10.3382\/ps\/pez215","article-title":"Effect of stocking density and dietary tryptophan on growth performance and intestinal barrier function in broiler chickens","volume":"98","author":"Goo","year":"2019","journal-title":"Poult. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1718","DOI":"10.1093\/ps\/80.12.1718","article-title":"Tryptophan requirements of different broiler genotypes","volume":"80","author":"Rosa","year":"2001","journal-title":"Poult. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2244","DOI":"10.14202\/vetworld.2021.2244-2250","article-title":"Immunomodulatory, behavioral, and nutritional response of tryptophan application on poultry","volume":"14","author":"Linh","year":"2021","journal-title":"Vet. World"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"471","DOI":"10.5713\/ab.22.0060","article-title":"Interaction between dietary digestible tryptophan and soy oligosaccharides in broiler chickens: Effects on caecal skatole level and microflora","volume":"36","author":"Chen","year":"2023","journal-title":"Anim. Biosci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"105955","DOI":"10.1016\/j.psj.2025.105955","article-title":"Effects of dietary tryptophan supplementation on growth performance, intestinal health, and AhR\/CYP1A1 signaling pathway in broiler chickens challenged with Clostridium perfringens","volume":"104","author":"Fan","year":"2025","journal-title":"Poult. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1093\/ps\/81.4.485","article-title":"Ideal ratio (relative to lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third weeks posthatch","volume":"81","author":"Baker","year":"2002","journal-title":"Poult. Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"851","DOI":"10.1016\/S0006-3223(98)00186-3","article-title":"Hypothalamic serotonin in control of eating behavior, meal size, and body weight","volume":"44","author":"Leibowitz","year":"1998","journal-title":"Biol. Psychiatry"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1007\/s11010-005-9103-5","article-title":"The effect of repeated tryptophan administration on body weight, food intake, brain lipid peroxidation and serotonin immunoreactivity in mice","volume":"286","author":"Ozer","year":"2006","journal-title":"Mol. Cell. Biochem."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Xie, K., Feng, X., Zhu, S., Liang, J., Mo, Y., Feng, X., Ye, S., Zhou, Y., Shu, G., and Wang, S. (2024). Effects of tryptophan supplementation in diets with different protein levels on the production performance of broilers. Animals, 14.","DOI":"10.3390\/ani14131838"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2094","DOI":"10.3382\/ps\/pey562","article-title":"Effect of different levels of tryptophan on productive performance, egg quality, blood biochemistry, and caecal microbiota of hens housed in enriched colony cages under commercial stocking density","volume":"98","author":"Khattak","year":"2019","journal-title":"Poult. Sci."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Saraf, M.K., Piccolo, B.D., Bowlin, A.K., Mercer, K.E., LeRoith, T., Chintapalli, S.V., Shankar, K., Badger, T.M., and Yeruva, L.A.-O. (2017). Formula diet driven microbiota shifts tryptophan metabolism from serotonin to tryptamine in neonatal porcine colon. Microbiome, 5.","DOI":"10.1186\/s40168-017-0297-z"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"e2309473","DOI":"10.1002\/advs.202309473","article-title":"Melatonin ameliorates depressive-like behaviors in ovariectomized mice by improving tryptophan metabolism via inhibition of gut microbe Alistipes Inops","volume":"11","author":"Zheng","year":"2024","journal-title":"Adv. Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"10184","DOI":"10.1039\/D1FO02172A","article-title":"Akkermansia muciniphila and its outer protein Amuc_1100 regulates tryptophan metabolism in colitis","volume":"12","author":"Gu","year":"2021","journal-title":"Food Funct."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Yusufu, I., Ding, K., Smith, K., Wankhade, U.D., Sahay, B., Patterson, G.T., Pacholczyk, R., Adusumilli, S., Hamrick, M.W., and Hill, W.D. (2021). A tryptophan-deficient diet induces gut microbiota dysbiosis and increases systemic inflammation in aged mice. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22095005"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1462","DOI":"10.1111\/jpn.13167","article-title":"Excess dietary tryptophan mitigates aflatoxicosis in growing quails","volume":"103","author":"Khanipour","year":"2019","journal-title":"J. Anim. Physiol. Anim. Nutr."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"700","DOI":"10.1080\/00071668.2019.1663494","article-title":"Development and reactivity of the immune system of Japanese quail lines divergently selected for the shape of the growth curve","volume":"60","author":"Kankova","year":"2019","journal-title":"Br. Poult. Sci."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1629","DOI":"10.1093\/jn\/117.9.1629","article-title":"Immunologically mediated growth depression in chicks: Influence of feed intake, corticosterone and interleukin-1","volume":"117","author":"Klasing","year":"1987","journal-title":"J. Nutr."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"699","DOI":"10.2527\/jas1987.653699x","article-title":"Comparative effects of individual amino acid excesses when added to a corn-soybean meal diet: Effects on growth and dietary choice in the chick","volume":"65","author":"Edmonds","year":"1987","journal-title":"J. Anim. Sci."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"118680","DOI":"10.1016\/j.jep.2024.118680","article-title":"Coptisine alleviates colitis through modulating gut microbiota and inhibiting TXNIP\/NLRP3 inflammasome","volume":"335","author":"Li","year":"2024","journal-title":"J. Ethnopharmacol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1186\/s13567-020-00755-3","article-title":"Akkermansia muciniphila protects intestinal mucosa from damage caused by S. pullorum by initiating proliferation of intestinal epithelium","volume":"51","author":"Zhu","year":"2020","journal-title":"Vet. Res."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"5806","DOI":"10.1039\/D1FO00659B","article-title":"Casein-fed mice showed faster recovery from DSS-induced colitis than chicken-protein-fed mice","volume":"12","author":"Yu","year":"2021","journal-title":"Food Funct."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Hu, X., Zhao, Y., Yang, Y., Gong, W., Sun, X., Yang, L., Zhang, Q., and Jin, M. (2020). Akkermansia muciniphila improves host defense against influenza virus infection. Front. Microbiol., 11.","DOI":"10.3389\/fmicb.2020.586476"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Hasani, A., Ebrahimzadeh, S., Hemmati, F., Khabbaz, A., Hasani, A., and Gholizadeh, P. (2021). The role of Akkermansia muciniphila in obesity, diabetes and atherosclerosis. J. Med. Microbiol., 70.","DOI":"10.1099\/jmm.0.001435"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1186\/s42523-021-00110-7","article-title":"The link between broiler flock heterogeneity and cecal microbiome composition","volume":"3","author":"Lundberg","year":"2021","journal-title":"Anim. Microbiome"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1007\/s12602-019-09557-2","article-title":"Effect of a potential probiotic candidate Enterococcus faecalis-1 on growth performance, intestinal microbiota, and immune response of commercial broiler chickens","volume":"12","author":"Shehata","year":"2020","journal-title":"Probiotics Antimicrob. Proteins"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"105307","DOI":"10.1016\/j.psj.2025.105307","article-title":"Effects of 3-indoleacrylic acid on alleviating lipopolysaccharide-induced liver inflammatory damage in laying hens","volume":"104","author":"Zhang","year":"2025","journal-title":"Poult. Sci."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Ji, Y., Yin, W., Liang, Y., Sun, L., Yin, Y., and Zhang, W. (2020). Anti-Inflammatory and Anti-Oxidative Activity of Indole-3-Acetic Acid Involves Induction of HO-1 and Neutralization of Free Radicals in RAW264.7 Cells. Int. J. Mol. Sci., 21.","DOI":"10.3390\/ijms21051579"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"3294","DOI":"10.1038\/s41467-018-05470-4","article-title":"Microbial tryptophan catabolites in health and disease","volume":"9","author":"Roager","year":"2018","journal-title":"Nat. Commun."}],"container-title":["Metabolites"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2218-1989\/15\/11\/736\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,11,11]],"date-time":"2025-11-11T13:11:43Z","timestamp":1762866703000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2218-1989\/15\/11\/736"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,11,11]]},"references-count":56,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2025,11]]}},"alternative-id":["metabo15110736"],"URL":"https:\/\/doi.org\/10.3390\/metabo15110736","relation":{},"ISSN":["2218-1989"],"issn-type":[{"value":"2218-1989","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,11,11]]}}}