DNA Methylation in Chickens: Molecular Patterns and Associations with Production Traits

Poultry production constitutes a major global source of animal protein. DNA methylation is an important epigenetic layer associated with economically relevant chicken traits, including fat deposition, muscle development, meat quality, reproduction, disease response, and environmental adaptation. This review integrates literature identified through searches of PubMed, Web of Science Core Collection, CNKI, and Wanfang through March 2026. CpG methylation predominates in the chicken methylome, whereas the reported contribution of non-CpG methylation varies across tissues and datasets. Promoters and CpG islands are generally hypomethylated, while gene bodies, repetitive elements, and intergenic regions are more highly methylated. Chicken studies support roles for DNMT-dependent maintenance methylation and TET-associated demethylation, but most trait-level evidence remains observational. Functional experiments have clarified selected loci and cell models, including cPouV, PLIN1, COL6A1, EBF1, and alternative PPARγ promoters. This review synthesizes methylation patterns, tissue specificity, and trait-associated evidence in chickens and distinguishes methylation-context composition from within-context methylation level.