Introduction For global commercial egg production it is estimated that over 75% of hens are reared in cages but new trends are emerging in rearing layers in animal-friendly systems. The alternative rearing systems have focused on developing better animal welfare and behavior for laying hens. In these systems, it is necessary that the system allow the birds to show their natural behaviors, decrease the probability of disease and injury, and increase productivity, egg quality, and food safety

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... However, production costs are important for producers and in alternative systems such as enriched-cage or no-cage systems production costs are high (2) and therefore salable egg number and also egg quality gain importance. Egg quality is an important factor influencing consumer purchase of eggs. In recent years, due to increasing awareness, consumers prefer to buy eggs with firm albumen, dense colored yolk, large size, and good quality (3). There are many genetic and environmental factors that affect both the internal and external quality of eggs. Today, alternative systems have become more important and the effect of these systems on egg quality parameters needs to be determined (4). Thus, studies have been conducted on effects of different housing systems, such as conventionalcage, enriched-cage, and outdoor systems, on external and internal egg quality characteristics (4,5). However, there are limited studies evaluating differences among housing systems for egg quality traits across a production cycle from placement of hens at the beginning of laying until depopulation (6,7). Thus, the aim of the current study was to determine effects of conventional-cage, enriched-cage, and free-range production systems and increasing flock age on external and internal egg quality characteristics of laying hens. Materials and methods The material for the current research was obtained from 480 layers (Lohmann Brown) housed in conventional-cage (CC), enriched-cage (EC), and free-range (FR) production systems between 22 and 60 weeks of age. A total of 720 eggs were analyzed for external and internal egg quality traits. The three housing systems were located within the same research unit of Uludağ University. Two cage systems, CC and EC, were installed in a windowed and fan-ventilated cage hen house with both cage types in the same room. The FR system was located 120 m from the cage hen house. The CC system consisted of galvanized wire cages (50 × 45 × 45 cm) with a trough-type galvanized feeder, egg belt, manure belt, and nipple drinker. Each CC cage provided a total of 562.5 cm 2 floor area per hen. The EC system cages met the requirements of EU Directive 1999/74/EC. The EC system consisted of 2 tiers, and each tier consisted of 2 cages (4 EC cages). The EC Abstract: The aim of this study was to investigate effects of conventional-cage (CC), enriched-cage (EC), and free-range (FR) systems and hen age on internal and external egg quality parameters of layers (Lohmann Brown). A total of 720 eggs were analyzed for egg weight (EW), shell weight (SW), yolk weight (YW), albumen weight (AW), shell thickness (ST), shell breaking strength (SBS), shape (SI), albumen (AI), yolk index (YI) of eggs, shell ratio of eggs (SR), albumen ratio of eggs (AR), yolk ratio of eggs (YR), yolk color (YC), and Haugh unit (HU). The highest EW, YW, AW, SW, AI, YI, HU (all P < 0.001), and SI values were found in FR system eggs compared with CC and EC system eggs (P = 0.045). The SBS, ST, YC, SR, YR, and AR were found similar in all housing systems. There was an interaction between the housing system and hen age for EW, SW, YW, AW, SBS, ST, AI, YC, HU, AR (all P < 0.001), SI (P = 0.003), SR (P = 0.001), and YR (P = 0.001) of eggs. It can be concluded that eggs in the FR system were better in overall quality than eggs from CC and EC systems.