<![CDATA[Double-yolked eggs are commonly observed in young laying hens at the onset of lay in commercial egg production, when reproductive maturation and irregular ovulation increase the likelihood of simultaneous ovulation. This narrative review compares single-yolked (SY) and double-yolked (DY) eggs, emphasizing their physical and compositional characteristics, embryo development, hatchability, and the biological and management factors influencing DY egg production. The DY production is influenced by laying age, breed, and management techniques such as light, nutrition and diet. Some niche markets may see DY eggs as a symbol of good luck and possibly a greeting. Nevertheless, in some cases, they are considered a defect in commercial production because of their fragility, inconsistent size, and reduced fertility and hatchability. Their lower shell strength increases breakage, resulting in economic losses. More importantly, DY embryos experience growth retardation. The larger size and volume of double-yolked eggs may reduce heat-transfer efficiency during incubation, potentially affecting embryonic temperature, developmental rate, and hatch-window duration. Producers may implement strategies, including genetic selection and breeding, nutritional management, optimized lighting and housing conditions, and routine flock monitoring, to minimize unnecessary double-yolked egg production. Overall, this review demonstrates that although double-yolked eggs differ from single-yolked eggs in their physical and compositional characteristics, embryo development, and hatchability, they may still have niche market value as table eggs despite their limited suitability for commercial hatchery production.]]>
