Effects of exposing eggs to green light during incubation on hatching and post-hatch performance in broiler chickens: a systematic review

It has been suggested that exposing eggs to green light during incubation is an approach that can enhance broiler performance; however, findings from published reports are inconsistent. Thus, this systematic review aimed to critically assess the effects of green-lighted incubation on embryonic development, hatchability, growth performance, and underlying physiological pathways in broiler chickens. A comprehensive literature search based on PRISMA guidelines identified 28 peer-reviewed papers published between 2002 and 2025. We extracted and synthesized data on mechanistic responses, production outcomes, and experimental settings. Overall, green-light incubation showed inconsistent but generally beneficial effects. Hatching and chick quality traits, including hatchability, embryo weight, organ weights, hatching time, and chick weight at hatch were frequently unaffected. On the other hand, growth performance, muscle development, and endocrine activity consistently improved, specifically via increased expression of growth-related genes and elevated levels of insulin-like growth factor-1 and growth hormone. In addition, some reports linked green light to better antioxidant status, earlier hatching, and faster embryonic growth. Nonetheless, greater variability was observed across studies in light intensity, photoperiod, embryonic stage at exposure, broiler strain, and the documenting of parameters such as breeder age and egg weight, which are likely sources of variation in reported results. Based on the review, green light might regulate broiler growth via molecular and endocrine pathways. Nevertheless, application and compatibility are limited by the absence of well-established methods, which has probably hindered adoption in commercial hatcheries. Thus, there is a need for future studies to focus on optimizing light conditions and clarifying mechanistic pathways.