Abstract
The aim of this study was to evaluate the effect of rearing system, genotype and hens age on egg weight and eggs components share. The tested rearing systems were the floor and organic, and tested genotypes were Isa Brown hybrid and New Hampshire breed. Eggs were collected for analyses three times in production cycle (32 weeks hens age, 48 weeks hens age, and 72 weeks hens age). In these samples (fifteen eggs per group, eggs were one day old) were investigated: egg weight, albumen share, yolk share and shell share. Egg weight was increased with hens age. Also, the interaction between the genotype and hens age was found, so the New Hampshire eggs in 32 weeks had less weight then Isa Brown eggs (p≤0.05), while in the 48 and 72 weeks this difference was lost (p≥0.05). The share of egg albumen and yolk was significantly affected by the rearing system, genotype and hens age (p≤0.05). Floor produced eggs had a lower proportion of albumen and a higher proportion of yolk compared to organic eggs. New Hampshire eggs had a higher content of yolk and the smaller content of albumen compared to Isa Brown eggs (p≤0.05). With hens age, the share of yolk was increased and albumen share was decreased. Interaction of all three studied factors - rearing system x genotype x hens age had the most important effect on the shell share.
Highlights
Cage rearing system is the dominant way of rearing of laying hens in most countries in the world, and this situation probably will continue for a long time
Egg weight was increased with hens age, so that the eggs from hens 32 weeks age had significantly lower weight (p≤0.05) compared to the eggs of hens 48 and 72 weeks age
The share of egg albumen and yolk was significantly affected by the rearing system, genotype and hens age (p≤0.05)
Summary
Cage rearing system is the dominant way of rearing of laying hens in most countries in the world, and this situation probably will continue for a long time The reason for this is because the rearing of hens in the cage is a most economical way of production, and it provides that the price of eggs is low and that product be accessible to all segments of the population. Statistics for 2013 did not record that in the big world egg producers such as Brazil, India, Iran, Mexico, Russia and Turkey laying hens were reared outside the cage (Windhorst, 2015) The exception of this trend is Europe, especially the EU countries wherein the cage system is reared only about 56% (with a decreasing trend) in the floor about 26%, in the so-called "free range" about 14% and about 4% of the birds are organic hens (Committee for the Common Organization of Agricultural Markets, 2016). There are two reasons for this situation in the European egg production: concern for the welfare of farmed animals and the awareness that the products produced in a natural way are better and healthier for the human consumption
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