The relationship between egg quality and hen housing systems-A systematic review

Although conventional battery hen cages are still prevalent in the global market, the movement towards greener methods is gaining momentum beyond Europe. However, egg quality and the degree to which it is affected by the different systems of production remains a controversial subject and there is still no consensus among researchers. Using PRISMA guidelines the literature reporting the housing systems effects of egg quality was systematically investigated. The related studies with different eggs production systems by databases including Web of Science, PubMed, and Scopus (between 1992 and 2020) were retrieved. Were adopted inclusion criteria, accepting studies that discussed measurable effects related to the topic that was written in English, Portuguese and Spanish. The search results which met the inclusion criteria were evaluated and included in the review In this regard, out of 3380 explored articles in the identification stage, 50 studies were used in the systematic review. Hen housing systems from different countries were recapped in this study. A brief outline of published scientific evidence demonstrates that the production system can change the egg quality. The overall rank order considering the type of system studied was cage (88%) > free-range (32%) > floor (30%) > organic (22%) and aviary (8%). Among the continents researched, Europe proved to have the most developed research relating to the subject. Egg weight was the most studied quality response. This study summarizes the housing system types used in egg production and provides a roadmap for future research regarding egg production. Robust trials evaluating different housing systems in the same conditions, and evaluating the interaction of factors such as genetics and age of animals, evaluating more responses of internal and external quality of eggs are lacking.