Effect of an organic and conventional rearing system on the mineral content of hen eggs K. Küçükyılmaz ⇑ , M. Bozkurt, Ç. Yamaner, M. Çınar, A.U. Çatlı, R. Konak Erbeyli Poultry Research Institute, 09600 _ Incirliova/Aydın, Turkey article info Article history: Received 20 April 2011 Received in revised form 26 October 2011 Accepted 16 November 2011 Available online 23 November 2011 Keywords: Organic Conventional Table hen egg Mineral content abstract In this study, the effect on mineral content of eggs from organic and conventional-housing systems was investigated. For this, random samples of 12 eggs were collected in both housing systems. Egg shells and edible portions were analysed for ash, Ca, P, Mg, Fe, Zn and Cu contents. The P and Zn contents of the edible egg portion were lower in the organic eggs than in conventional eggs. Mg content of the eggshell was higher in organic eggs while Zn content showed a marked decrease. As far as Ca, Fe and Cu values were concerned, these did not differ between the eggs from organic and conventional systems. The results showed considerable differences in mineral content between the eggs from the hens reared in organic and conventional systems. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The organic egg production system is based on specific and pre- cise standards of production, and this farming technique is progres- sively increasing in popularity. Briefly, organic eggs can be defined as the product of a rearing system that absolutely avoids conven- tionally grown feedstuffs, including genetically modified organisms, animal by-products and synthetic additives, while using only organ- ically grown cereals, oil, seeds and roughage. The system also pro- vides chickens with free access to outdoor areas with a lower rearing intensity (Hermansen, 2003; Sundrum, 2001; Van De Weerd, Keatinge, & Roderick, 2009). There are many factors that influence the purchase and con- sumption of eggs produced by an organic system. Many consumers believe that eggs originating from organic farms taste better and have a higher nutritional value (Kouba, 2003; Rodic, Peric, Vukelic, & Milosevic, 2006). Therefore, consumers expect to pay more for organically produced eggs than for conventional eggs. It is impor- tant for producers and consumers to be informed about the effects of the organic system on the nutritional composition and quality of the eggs, but the number of studies on this subject is still limited. Organic eggs are expected to have better nutritional values than conventional eggs due to the chickens’ free access to the outdoors and organic feed consumption. Considering the increasing concern regarding organic hen eggs, some studies have recently shown effects of different housing systems on egg composition (Cerolini, Zaniboni, & La Cognata, 2005; Hidalgo, Rossi, Clerici, & Ratti, 2008; Minelli, Sirri, Folegatti, Meluzzi, & Franchini, 2007; Rizzi, Simioli, Martelli, Paganelli, & Sardi, 2006; Samman et al., 2009). However, data on the levels of macro and micro minerals in eggs from organic housing systems are very limited. Two previous stud- ies have shown that organic systems could affect the mineral content of eggs (Giannenas, Nisianakis, Gavrill, Kontopidis, & Kyriazakis, 2009; Matt, Veromann, & Luik, 2009). The aim of the current study was to assess differences amongst macro and trace element concentrations in table eggs from hens reared in different husbandry systems, namely conventional cage facility and organic production system. 2. Materials and methods 2.1. Animals, housing and diets In total, 416 brown laying hens of native hybrid (ATAK-S), layers at 23 weeks of age, were used as the animal material in this study. The trial was performed between January, 2008 and November, 2008, under sub-tropical conditions in the south Aegean region of Turkey. Hens were housed either in conventional cages or in the organic rearing system. In the conventional rearing system, 216 hens, having mean body weight 2242 g, were randomly assigned to six replications of triple-deck battery cages that were equipped with linear feeders and nipple drinkers. Each replication consisted of six cages (36 hens per replication), and the hens of six adjacent cages were considered a replication. Hens were kept in cages (50 cm length, 60 cm width, 56 cm height) with six hens per cage, providing 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.11.084 ⇑ Corresponding author. Tel./fax: +90 256 581 1123. E-mail address: kamilkucukyilmaz@hotmail.com (K. Küçükyılmaz). Food Chemistry 132 (2012) 989–992 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem