Abstract
The aim of this study was to evaluate the effect of rearing system and hen's age on quality and chemical composition of eggs. The tested rearing systems were: cage, floor and organic (30 birds Isa Brown hybrid per group). Fifteen eggs per group were collected for analyses in each of three phases of the productive cycle (32, 48 and 72 weeks hen's age). In these samples were investigated external (egg weight and egg shape index), internal (albumen height, Haugh unit and yolk colour) and chemical composition of eggs (dry matter, minerals, protein and lipids content). The general conclusion is that the egg weight and Roche values were increased, while egg shape index, albumen height and Haugh unit were decreased with hen's age. Organic eggs had higher albumen height and more Haugh units in the 48 and 64 weeks compared to the floor and cage eggs. Yolk colour of the floor and cage hens most dependent on the hen's age, on the other hand - yolk colour of organic hens most dependent on the grass availability at the outlet. Eggs from the organic rearing system had a lower dry matter, proteins and lipid content as compared to the cage system.
Highlights
Producers around the world are increasingly converting their facilities to cage-free, data from the International Egg Commission (2016) show that the majority of laying hens (89.7%) are housed in a cage system
The general conclusion is that the egg weight and Roche values were increased, while egg shape index, albumen height and Haugh unit were decreased with hen's age
Egg weight was increased with hen's age, which is consistent with the results published by Zita et al (2009) and Rakonjac et al (2017)
Summary
Producers around the world are increasingly converting their facilities to cage-free, data from the International Egg Commission (2016) show that the majority of laying hens (89.7%) are housed in a cage system. In the report of Committee for the Common Organisation of the Agricultural Markets (2018), it is stated that in the EU countries 18.4% of the hens have access to an outlet (free range and organic together). Due to all these facts, the aim of this study was to evaluate the effect of rearing system and hen's age on quality and chemical composition of eggs
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