_1776544959 20260418204239000 Rovedar Daryoushbabazadeh@gmail.com Rovedar Journal of World’s Poultry Science J. World's Poult. Sci. 2980-7999 03 05 2026 5 1 Emeka Austin Anyigor https://orcid.org/0000-0002-1153-5081 Eleleh Oluchi Jecinta https://orcid.org/0009-0003-5864-1847 Ifeanyi Princewell Ogbuewu https://orcid.org/0000-0003-4895-7867 Edeheudim Bassey Etuk https://orcid.org/0000-0003-3385-8006 Modulating the gut microbiome is critical for maintaining the health and productivity of laying hens. Nutritional interventions are essential for preserving gut integrity under the pressures of high egg production and alternative housing systems. The present study aimed to provide a comprehensive synthesis of current knowledge on the relationship between nutritional strategies and gut microbiome modulation and productivity in laying hens. A systematic literature search of PubMed, Scopus, and ScienceDirect (2015-2026) retrieved 108 studies that met the eligibility criteria for qualitative analysis. The inclusion of probiotics, prebiotics, organic acids, exogenous enzymes, vitamins, minerals, and amino acids in laying hen diets was associated with improved microbial balance, intestinal function, immune status, and nutrient utilization, resulting in greater egg production and egg quality. These nutritional approaches provided sustainable alternatives to antibiotic growth promoters, supporting resilient egg production systems by improving gut health and maintaining productive performance in laying hens. Productive performance, short‑chain fatty acid production, and reduced pathogenic colonization in laying hens were all positively influenced by nutritional interventions that effectively modulate the gut microbiome. 03 31 2026 9 16 https://creativecommons.org/licenses/by/4.0 10.58803/jwps.v5i1.116 https://jwps.rovedar.com/index.php/JWPS/article/view/116 https://jwps.rovedar.com/index.php/JWPS/article/download/116/120 https://jwps.rovedar.com/index.php/JWPS/article/download/116/120 Food and agriculture organization of the united nations (FAO). Agribusiness handbook: Poultry meat and eggs. Food And Agriculture Organizations of The United Nations, 2023. Available at: https://openknowledge.fao.org/bitstreams/c548c19f-b615-45fe-a55c-5fb7404715d3/download Korver DR. Review: Current challenges in poultry nutrition, health, and welfare. Animal. 2023; 17(Suppl 2): 100755. DOI: 10.1016/j.animal.2023.100755 Dai D, Qi GH, Wang J, Zhang HJ, Qiu K, and Wu SG. Intestinal microbiota of layer hens and its association with egg quality and safety. Poult Sci. 2022; 101(9): 102008. DOI: 10.1016/j.psj.2022.102008 Desbruslais A, Wealleans A, Gonzalez-Sanchez D, and di Benedetto M. Dietary fibre in laying hens: A review of effects on performance, gut health and feather pecking. World’s Poult Sci J. 2021; 77(4): 797-823. DOI: 10.1080/00439339.2021.1960236 Mulder ND. Global egg industry outlook 2035: Long-term egg market and investment perspectives. World Egg Organisation, 2025. Available at: https://www.rabobank.com/knowledge/q011497178-global-egg-industry-outlook-2035-long-term-egg-market-and-investment-perspectives ISA brown management guide. Boxmeer, Netherlands: Institute for Animal Breeding; 2019. Available at: https://www.scribd.com/document/513752045/isa-brown-product-guide-cage-production-systems-vs1408a Lohmann breeders. Outstanding performances: LOHMANN layers above the standards. Lohmann Breeders, 2025. Available at: https://lohmann-breeders.com/outstanding-performances-lohmann-layers-above-the-standards/ Kidd MT, and Anderson KE. Laying hens in the U.S. market: An appraisal of trends from the beginning of the 20th century to present. J Appl Poult Res. 2019; 28(4): 771-784. DOI: 10.3382/japr/pfz043 Aruwa CE, and Sabiu S. Interplay of poultry-microbiome interactions - influencing factors and microbes in poultry infections and metabolic disorders. Br Poult Sci. 2024; 65(5): 523-537. DOI: 10.1080/00071668.2024.2356666 Feng J, Lu M, Wang J, Zhang HJ, Qiu K, Qi GH, et al. Dietary oregano essential oil supplementation improves intestinal functions and alters gut microbiota in late-phase laying hens. J Anim Sci Biotechnol. 2021; 12: 1-15. DOI: 10.1186/s40104-020-00529-3 Singh AK, and Kim WK. Effects of dietary fiber on nutrients utilization and gut health of poultry: A review of challenges and opportunities. Animals. 2021; 11(1): 181. DOI: 10.3390/ani11010181 El Jeni R, Dittoe DK, Olson EG, Lourenco J, Corcionivoschi N, Ricke SC, et al. Probiotics and potential applications for alternative poultry production systems. Poult Sci. 2021; 100(7): 101156. DOI: 10.1016/j.psj.2021.101156 Kers JG, Velkers FC, Fischer EAJ, Hermes GDA, Stegeman JA, and Smidt H. Host and environmental factors affecting the intestinal microbiota in chickens. Front Microbiol. 2018; 9: 235. DOI: 10.3389/fmicb.2018.00235 Pin Viso N, Redondo E, Díaz Carrasco JM, Redondo L, Garcia JS, Miyakawa MF, et al. Geography as non-genetic modulation factor of chicken cecal microbiota. PLOS ONE. 2021; 16(1): e0244724. DOI: 10.1371/journal.pone.0244724 Khan S, Moore RJ, Stanley D, Chousalkar KK. The gut microbiota of laying hens and its manipulation with prebiotics and probiotics to enhance gut health and food safety. Appl Environ Microbiol. 2020; 86(13): e00600-20. DOI: 10.1128/aem.00600-20 Bernard M, Lecoeur A, Coville JL, Bruneau N, Jardet D, Lagarrigue S, et al. Relationship between feed efficiency and gut microbiota in laying chickens under contrasting feeding conditions. Sci Rep. 2024; 14: 8210. DOI: 10.1038/s41598-024-58374-3 Ballou AL, Ali RA, Mendoza MA, Ellis JC, Hassan HM, Croom WJ, et al. Development of the chick microbiome: How early exposure influences future microbial diversity. Front Vet Sci. 2016; 3: 2. DOI:10.3389/fvets.2016.00002 Nafady AA, Ghoneim SS, Behour TS, Akhtar M, Youssef IM, Abd-Elkareem M, et al. Comparative study of gut microbiota profiles and reproductive traits in high- and low-laying chickens. Poult Sci. 2025; 104(12): 105991. DOI: 10.1016/j.psj.2025.105991 Ding J, Dai R, Yang L, He C, Xu K, Liu S, et al. Inheritance and establishment of gut microbiota in chickens. Front Microbiol. 2017; 8: 1967. DOI: 10.3389/fmicb.2017.01967 Lee S, La TM, Lee HJ, Choi IS, Song CS, Park SY, et al. Characterization of microbial communities in the chicken oviduct and the origin of chicken embryo gut microbiota. Sci Rep. 2019; 9(1): 6838. DOI: 10.1038/s41598-019-43280-w Kogut MH. The effect of microbiome modulation on the intestinal health of poultry. Anim Feed Sci Technol. 2019; 250: 32-40. DOI: 10.1016/j.anifeedsci.2018.10.008 Zhang JM, Sun YS, Zhao LQ, Chen TT, Fan MN, Jiao HC, et al. SCFAs-induced GLP-1 secretion links the regulation of gut microbiome on hepatic lipogenesis in chickens. Front Microbiol. 2019; 10: 2176. DOI: 10.3389/fmicb.2019.02176 Kim HR, Ryu C, Lee SD, Cho JH, and Kang H. Effects of heat stress on the laying performance, egg quality, and physiological response of laying hens. Animals. 2024; 14(7): 1076. DOI: 10.3390/ani14071076 Shehata AA, Yalçın S, Latorre JD, Basiouni S, Attia YA, Abd El-Wahab A, et al. Probiotics, prebiotics, and phytogenic substances for optimizing gut health in poultry. Microorganisms. 2022; 10(2): 395. DOI: 10.3390/microorganisms10020395 Markowiak P, and Śliżewska K. The role of probiotics, prebiotics and synbiotics in animal nutrition. Gut Pathog. 2018; 10(1): 21. DOI: 10.1186/s13099-018-0250-0 Pineda-Quiroga C, Borda-Molina D, Chaves-Moreno D, Ruiz R, Atxaerandio R, Camarinha-Silva A, et al. Microbial and functional profile of the ceca from laying hens affected by feeding prebiotics, probiotics, and synbiotics. Microorganisms. 2019; 7: 123. DOI: 10.3390/microorganisms7050123 Onbaşılar EE, Yalçın S, Bakıcı C, Batur B, Kartal YK, Ahlat O, et al. Comprehensive evaluation of probiotic effects on laying hen physiology: From performance to bone and gut morphology. Animals. 2025; 15(16): 2408. DOI: 10.3390/ani15162408 Liu L, Zhang G, Qu G, Liu B, Zhang X, Li G, et al. Effects of dietary Lactobacillus rhamnosus GG supplementation on the production performance, egg quality, eggshell ultrastructure, and lipid metabolism of late-phase laying hens. BMC Vet Res. 2023; 19(1): 150. DOI: 10.1186/s12917-023-03719-9 Dangsawat O, Rattanawut J, Srisawat T, Sowanpreecha R, Tang Phuc Khang L, Srinual O, et al. Bacillus aryabhattai CKNJh11 as a promising probiotic improves growth performance and egg quality in laying hens. Sci Rep. 2025; 15: 13659. DOI: 10.1038/s41598-025-97553-8 Tajudeen H, Ha SH, Hosseindoust A, Mun JY, Park S, Park S, et al. Effect of dietary inclusion of Bacillus-based probiotics on performance, egg quality, and the faecal microbiota of laying hen. Anim Biosci. 2024; 37(4): 689-696. DOI: 10.5713/ab.23.0299 Neijat M, Shirley RB, Barton J, Thiery P, Welsher A, and Kiarie E. Effect of dietary supplementation of Bacillus subtilis DSM29784 on hen performance, egg quality indices, and apparent retention of dietary components in laying hens from 19 to 48 weeks of age. Poult Sci. 2019; 98(11): 5622-5635. DOI: 10.3382/ps/pez324 Hakami ZM, Alhotan RA, Al-Sulaiman AR, Aljumaah RS, Palombo V, D'Andrea M, et al. Enhancing laying hen productivity and health: Influence of dietary probiotic Bacillus strains and prebiotic Saccharomyces cerevisiae yeast cell wall on production performance, egg quality, and inflammatory responses. Animals. 2025; 15(10): 1398. DOI: 10.3390/ani15101398 Fathima S, Shanmugasundaram R, Sifri M, and Selvaraj R. Yeasts and yeast-based products in poultry nutrition. J Appl Poult Res. 2023; 32(2): 100345. DOI: 10.1016/j.japr.2023.100345 Abd El-Ghany WA. Yeasts and their derivatives as functional feed additives in poultry nutrition. Agriculture. 2025; 15(9): 1003. DOI: 10.3390/agriculture15091003 Gibson GR, Hutkins R, Sanders ME, Prescott SL, Reimer RA, Salminen SJ, et al. Expert consensus document: The international scientific association for probiotics and prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017; 14(8): 491-502. DOI: 10.1038/nrgastro.2017.75 Morgan NK. Advances in prebiotics for poultry: Role of the caeca and oligosaccharides. Anim Prod Sci. 2023; 63(18): 1911-1925. DOI: 10.1071/AN23011 Petranyi F, Whitton MM, Lobo E, Ramirez S, Radovanović A, Bajagai YS, et al. Precision glycan supplementation: A strategy to improve performance and intestinal health of laying hens in high-stress commercial environments. J Anim Physiol Anim Nutr (Berl). 2024; 108(5): 1498-1509. DOI: 10.1111/jpn.13996 Youssef IM, Aldhalmi AK, Felemban SG, Elsherbeni AI, Khalil HA, Hassan MS, et al. Mannan oligosaccharides as a prebiotic for laying hens: Effects on fertility, hatchability, productive performance, and immunity. Transl Anim Sci. 2024; 8: txae123. DOI: 10.1093/tas/txae123 Zhou J, Wu S, Qi G, Fu Y, Wang W, Zhang H, et al. Dietary supplemental xylooligosaccharide modulates nutrient digestibility, intestinal morphology, and gut microbiota in laying hens. Anim Nutr. 2021; 7(1): 152-162. DOI: 10.1016/j.aninu.2020.05.010 Mahmood T, and Guo Y. Dietary fiber and chicken microbiome interaction: Where will it lead to? Anim Nutr. 2020; 6(1): 1-8. DOI: 10.1016/j.aninu.2019.11.004 Dibakoane SR, Mhlongo G, Moonsamy G, Wokadala OC, Mnisi CM, and Mlambo V. Phenomenological and mechanistic insights into potential dietary nucleotide-probiotic synergies in layer chickens: A review. Poult Sci. 2025; 104(5): 105049. DOI: 10.1016/j.psj.2025.105049 Naeem M, and Bourassa D. Probiotics in poultry: Unlocking productivity through microbiome modulation and gut health. Microorganisms. 2025; 13(2): 257. DOI: 10.3390/microorganisms13020257 Dittoe DK, Ricke SC, and Kiess AS. Organic acids and potential for modifying the avian gastrointestinal tract and reducing pathogens and disease. Front Vet Sci. 2018; 5: 216. DOI: 10.3389/fvets.2018.00216 Gerzilov V, and Hristakieva P. Organic acids supplementation in poultry nutrition: A review. Open Vet J. 2025; 15(8): 3448-3458. DOI: 10.5455/OVJ.2025.v15.i8.8 Rezaeipour M, Afsharmanesh M, and Bami MK. Evaluation of the effect of short-chain organic acids and probiotics on production performance, egg white quality, and fecal microbiota of laying hens. Comp Clin Pathol. 2022; 31: 621-626. DOI: 10.1007/s00580-022-03360-2 Markazi AD, Luoma A, Shanmugasundaram R, Murugesan R, Mohnl M, and Selvaraj R. Effect of acidifier product supplementation in laying hens challenged with Salmonella. J Appl Poult Res. 2019; 28(4): 919-929. DOI: 10.3382/japr/pfz053 Lee J, Oh S, and Heo JM. Application of dietary organic acids in laying hens production: A comprehensive review. J Anim Sci Technol. 2025; 67(6): 1185-1206. DOI: 10.5187/jast.2500224 Zhou Y, Qiu C, Zhou Z, Zhang Y, Zhang D, Cai Y, et al. Baicalein and citric acid modulate intestinal morphology and health status in laying hens. Vet Sci. 2025; 12(8): 706. DOI: 10.3390/vetsci12080706 Vargas-Rod LM, Herrera JG, Morales EJ, Arcos-Garc JL, Lopez-Pozo R, and Ruelas G. Effect of citric acid, phytase and calcium in diets of laying hens on productive performance, digestibility and mineral excretion. Int J Poult Sci. 2015; 14(4): 222-228. DOI: 10.3923/ijps.2015.222.228 Warsito SH, Lamid M, Al-Arif MA, Hermadi HA, Sabdoningrum EK, Ayuti SR, et al. The results of intestinal villi of laying hens exposed with avian pathogenic Escherichia coli (APEC) after giving citric acid and dextrose. Vet Med Int. 2025; 2025: 6623764. DOI: 10.1155/vmi/6623764 Abd El-Ghany WA. Applications of organic acids in poultry production: An updated and comprehensive review. Agriculture. 2024; 14(10): 1756. DOI: 10.3390/agriculture14101756 Khan SH, and Iqbal J. Recent advances in the role of organic acids in poultry nutrition. J Appl Anim Res. 2016; 44(1): 359-369. DOI: 10.1080/09712119.2015.1079527 Macambira GM, Rabello CBV, Oliveira HS de H, Dos Santos MJB, Ribeiro AG, Lins Júnior OS, et al. Effects of xylanase and phytase supplementation in diets containing Moringa oleifera leaf meal on intestinal morphology and the relative size and weight of internal organs of laying hens. Front Vet Sci. 2025; 12: 1615214. DOI: 10.3389/fvets.2025.1615214 Mun JY, Tajudeen H, Silvestre PN, Ha SH, Hosseindoust A, Lokhande A, et al. Multienzyme supplementation alleviates the performance of hens fed diets with lower crude protein and energy levels during peak to late production phase. Poult Sci. 2025; 104(11): 105823. DOI: 10.1016/j.psj.2025.105823 Kayan A, Prasongsook S, and Poeikhampha T. Diet supplementation with phytase and xylanase on laying performance, egg quality, apparent metabolizable energy, and phosphorous use in laying hens. Vet World. 2025; 18(1): 155-161. DOI: 10.14202/vetworld.2025.155-161 Poudel I, Hodge VR, Wamsley KGS, Roberson KD, and Adhikari PA. Effects of protease enzyme supplementation and varying levels of amino acid inclusion on productive performance, egg quality, and amino acid digestibility in laying hens from 30 to 50 weeks of age. Poult Sci. 2023; 102(3): 102465. DOI: 10.1016/j.psj.2022.102465 Oketch EO, Yu M, Nawarathne SR, Chaturanga NC, Maniraguha V, Sta Cruz BG, et al. Multiprotease supplementation in laying hen diets: Impact on performance, egg quality, digestibility, gut histomorphology, and sustainability. Poult Sci. 2025; 104(4): 104977. DOI: 10.1016/j.psj.2025.104977 Walker H, Bauer K, Cvejić D, Keegan JD, Nikodinoska I, Taylor-Pickard J, et al. Allzyme® Spectrum supplementation improves apparent ileal phosphorus digestibility and retention in older laying hens. J Appl Anim Nutr. 2025; 1-9. DOI: 10.1163/2049257x-20241014 Chen Y, Li X, Zhang H, Bai X, Ding J, Ye D, et al. Effects of vitamins A and C on intestinal immunity and gut microbiota in poultry. Front Microbiol. 2023; 14: 1180838. DOI: 10.3389/fmicb.2023.1180838 Sharma MK, Lee J, Shi H, Ko H, Goo D, Paneru D, et al. Effect of dietary inclusion of 25-hydroxyvitamin D₃ and vitamin E on performance, gut health, oxidative status, and immune response in laying hens infected with coccidiosis. Poult Sci. Poult Sci. 2024; 103(9): 104033. DOI: 10.1016/j.psj.2024.104033 Ouyang J, Zhang C, Deng C, Wen A, Zhou H, You J, et al. Dietary vitamin B6 supplementation alleviates heat stress-induced intestinal barrier impairment by regulating the gut microbiota and metabolites in broilers. Poult Sci. 2024; 103(11): 104202. DOI: 10.1016/j.psj.2024.104202 Wang X, Bai S, Yang F, Wu D, Li L. Comparison of production performance, egg quality, and cecal microbiota in laying hens receiving graded levels of vitamin B12. Poult Sci. 2021; 100(11): 100982. DOI: 10.1016/j.psj.2021.100982 Wang C, Shan H, Chen H, Bai X, Ding J, Ye D, et al. Probiotics and vitamins modulate the cecal microbiota of laying hens submitted to induced molting. Front Microbiol. 2023; 14: 1180838. DOI: 10.3389/fmicb.2023.1180838 Akter N, Dao TH, Crowley TM, Sukirno, Nawab A, and Moss AF. Afternoon calcium and vitamin D supplementation in water: A targeted approach to improve laying hen nutrition. Animals. 2025; 15(5): 72. DOI: 10.3390/ani15050720 Gao ZQ, Su JW, Qin Y, Ye T, Cao H, Yang LH, et al. Metagenomic analysis of vitamins B and K2 biosynthesis in chicken gut microbiota across laying periods. BMC Microbiol. 2025; 25: 553. DOI: 10.1186/s12866-025-04296-7 Halder M, Petsophonsakul P, Akbulut AC, Pavlic A, Bohan F, Anderson E, et al. Vitamin K: Double bonds beyond coagulation insights into differences between vitamin K1 and K2 in health and disease. Int J Mol Sci. 2019; 20(4): 896. DOI: 10.3390/ijms20040896 Muhammad AI, Mohamed DAA, Chwen LT, Akit H, and Samsudin AA. Effect of sodium selenite, selenium yeast, and bacterial enriched protein on chicken egg yolk color, antioxidant profiles, and oxidative stability. Foods. 2021; 10(4): 871. DOI: 10.3390/foods10040871 Sinclair-Black M, Garcia RA, and Ellestad LE. Physiological regulation of calcium and phosphorus utilization in laying hens. Front Physiol. 2023; 14: 1112499. DOI: 10.5713/ab.22.0086 Elnesr SS, Mahmoud BY, da Silva Pires PG, Moraes P, Elwan HAM, El-Shall NA, et al. Trace minerals in laying hen diets and their effects on egg quality. Biol Trace Elem Res. 2024; 202(12): 5664-5679. DOI: 10.1007/s12011-024-04121-8 Dong Y, Zhang K, Han M, Miao Z, Liu C, and Li J. Low level of dietary organic trace minerals improved egg quality and modulated the status of eggshell gland and intestinal microflora of laying hens during the late production stage. Front Vet Sci. 2022; 9: 920418. DOI: 10.3389/fvets.2022.920418 Wlaźlak S, Pietrzak E, Biesek J, and Dunislawska A. Modulation of the immune system of chickens a key factor in maintaining poultry production - a review. Poult Sci. 2023; 102(8): 102785. DOI: 10.1016/j.psj.2023.102785 Belkameh MM, Sedghi M, and Azarfar A. The effect of different levels of dietary magnesium on eggshell quality and laying hen’s performance. Biol Trace Elem Res. 2021; 199(4): 1566-1573. DOI: 10.1007/s12011-020-02259-9 Ogbuewu IP, and Mbajiorgu CA. Meta-analysis of zinc supplementation on laying performance, egg quality characteristics, and blood zinc concentrations in laying hens. Biol Trace Elem Res. 2022; 200(12): 5188-5204. DOI: 10.1007/s12011-021-03080-8 Niknia AD, Vakili R, and Tahmasbi AM. Zinc supplementation improves antioxidant status, and organic zinc is more efficient than inorganic zinc in improving the bone strength of aged laying hens. Vet Med Sci. 2022; 8(5): 2040-2049. DOI: 10.1002/vms3.896 Qin K, Cong X, Wang H, Yan M, Xu X, Liu M, et al. Effects of supplementing selenium-enriched Cardamine violifolia to laying hens on egg quality and yolk antioxidant capacity during storage at 4 °C and 25 °C. Foods. 2024; 13(5): 802. DOI: 10.3390/foods13050802 Surai PF, and Kochish II. Nutritional modulation of the antioxidant capacities in poultry: The case of selenium. Poult Sci. 2019; 98(10): 4231-4239. DOI: 10.3382/ps/pey406 Abbas G, Ahmad F, Saeed M, Ayasan T, Mahmood A, Yasmeen R, et al. Effect of dietary inclusion of sodium bicarbonate on digestibility of nutrients and immune response in caged layers during the summer. Rev Bras Cienc Avic. 2019; 21(2): 1-8. DOI: 10.1590/1806-9061-2018-0915 Sarlak S, Tabeidian SA, Toghyani M, Shahraki ADF, Goli M, and Habibian M. Organic iron and iodine in laying hen diet: Performance, egg quality, thyroid hormones, antioxidant status, serum and yolk lipids, and egg iron and iodine contents. J Trace Elem Miner. 2025; 11: 100211. DOI: 10.1016/j.jtemin.2025.100211 Słupczyńska M, Jamroz D, Orda J, Wiliczkiewicz A, Kuropka P, and Król B. The thyroid hormone and immunoglobulin concentrations in blood serum and thyroid gland morphology in young hens fed with different diets, sources, and levels of iodine supply. Animals. 2022; 13(1): 158. DOI: 10.3390/ani13010158 Cao J, Zhu J, Zhou Q, Zhao L, Zou C, Guo Y, et al. Efficacy evaluation of novel organic iron complexes in laying hens: Effects on laying performance, egg quality, egg iron content, and blood biochemical parameters. Anim Biosci. 2023; 36(3): 498-505. DOI: 10.5713/ab.22.0086 da Silva JVC, de Lima AV, de Brito ANEF, Ferreira T da S, Kaneko IN, Pascoal LAF, et al. Effect of supplementation with different sources and levels of zinc, copper, and manganese on the reproductive development of laying hens. Poult Sci. 2025; 104(8): 105306. DOI: 10.1016/j.psj.2025.105306 Ma N, Liu M, Song M, Li S, Lin X, Jiao H, et al. The application of copper waterline on laying performance and gut health of aged laying hens. J Poult Sci. 2022; 59(3): 223-232. DOI: 10.2141/jpsa.0210124 Gong C, Shi H, Liu S, Gao X, Zhang S, Liu H, et al. Determination of optimal dietary calcium levels under different sources of zinc in Jing tint 6 layer chicks from 15 to 42 d of age. Poult Sci. 2024; 103(11): 104192. DOI: 10.1016/j.psj.2024.104192 Umar Yaqoob M, Wang G, Sun W, Pei X, Liu L, Tao W, et al. Effects of inorganic trace minerals replaced by complexed glycinates on reproductive performance, blood profiles, and antioxidant status in broiler breeders. Poult Sci. 2020; 99(5): 2718-2726. DOI: 10.1016/j.psj.2019.11.058 Santos MJB, Ludke MCMM, Silva LM, Rabello CBV, Barros MR, Costa FS, et al. Complexed amino acid minerals vs. bis-glycinate chelated minerals: Impact on the performance of old laying hens. Anim Nutr. 2024; 16: 395-408. DOI: 10.1016/j.aninu.2023.11.006 Alabi T, and Adedokun S. Amino acid nutrition in poultry: A review. Animals. 2025; 15(22): 3323. DOI: 10.3390/ani15223323 Alagawany M, Elnesr SS, Farag MR, Tiwari R, Yatoo MI, Karthik K, et al. Nutritional significance of amino acids, vitamins and minerals as nutraceuticals in poultry production and health - a comprehensive review. Vet Q. 2020; 41(1): 1-29. DOI: 10.1080/01652176.2020.1857887 Liu G, and Kim WK. The functional roles of methionine and arginine in intestinal and bone health of poultry: Review. Animals. 2023; 13(18): 2949. DOI: 10.3390/ani13182949 Ma M, Geng S, Liu M, Zhao L, Zhang J, Huang S, et al. Effects of different methionine levels in low protein diets on production performance, reproductive system, metabolism, and gut microbiota in laying hens. Front Nutr. 2021; 8: 739676. DOI: 10.3389/fnut.2021.739676 Reda FM, Swelum AA, Hussein EOS, Elnesr SS, Alhimaidi AR, and Alagawany M. Effects of varying dietary DL-methionine levels on productive and reproductive performance, egg quality, and blood biochemical parameters of quail breeders. Animals. 2020; 10(10): 1839. DOI: 10.3390/ani10101839 Wang C, Liu X, Sun X, Li Y, Yang X, and Liu Y. Dietary betaine supplementation improved egg quality and gut microbes of laying hens under dexamethasone-induced oxidative stress. Poult Sci. 2024; 103(11): 104178. DOI: 10.1016/j.psj.2024.104178 Mikulewicz M, Chojnacka K, Kawala B, and Gredes T. Trace elements in living systems: From beneficial to toxic effects. Biomed Res Int. 2017; 2017: 8297814. DOI: 10.1155/2017/8297814