Effect of the laying hen's age on the quality of organic eggs

Abstract

Organic poultry production is one of the sectors of organic livestock production with the fastest growing rate. Numerous scientific studies have established the superior quality of organic eggs, however, it is not constant and is more impacted by environmental factors than commercially produced eggs. In addition to genotype, the greatest effect on the quality of organic eggs is the season, the quality of the discharge, and the stage of the production cycle of reared layers. For this reason, this paper aimed to examine the effect of age and stage of the production cycle on the quality of organic eggs. The eggs of the New Hampshire dual-purpose breed were examined. In the 24th, 40th and 56th weeks of the laying hen's age, 15 eggs each were collected to determine the selected egg quality parameters (egg weight, Haugh units, yolk colour and shell breaking strength) and the basic chemical composition of eggs (content of dry matter, minerals, protein and lipids). The egg weight increased with the hen's age - 51.39 g in the 24th week, 63.85 g in the 40th week and 66.93 g in the 56th week (p≤0.05). On the other hand, the number of Haugh units decreased continuously with the ageing of the laying hens, from 94.53 in the 24th week, over 84.27 in the 40th, to 78.87 in the 56th week (p≤0.05). The hens aged 48 weeks (12.07 Roshe point; p≤0.05) had the most intensively coloured yolk, while there was no significant difference in this trait between 24 (11.20 Roshe) and 56-week-old hens (11.07 Roshe; p≥0.05). The shell breaking strength was the only investigated parameter that was not significantly affected by the hen's age (36.81 N at 24, 38.44 N at 40, and 36.23 N at 56 weeks; p≥0.05). The content of dry matter and lipids increased significantly and continuously with the ageing of hens (22.29% dry matter and 7.69% lipids in the 24th week; 24.10% dry matter and 9.61% lipids in the 40th week and 25.06% dry matter and 10.37% lipids in the 56th week; p≤0.05). Eggs of 56-week-old laying hens had a significantly higher mineral content (0.93%; p≤0.05) compared to 40-week-old (0.83%) and 24-week-old hens (0.86%). Only the protein content decreased with the hens ageing, so the eggs of 24-week-old layers had a significantly higher content of this fraction (12.94%; p≤0.05) compared to the eggs of hens aged 40 (12.14%) and 56 weeks (12.41%), which did not differ significantly from each other (p≥0.05).