Analysis of changes in egg quality of broiler breeders during the first reproduction period

In reproductive flocks of poultry it is very important to obtain a large number of eggs with normal structure, optimal morphological composition and interior quality. These elements have very significant influence on the biological value of the egg, which determines normal development of the embryo. The aim of the study was to analyse the physical characteristics, morphological composition and quality of individual components of the eggs of Cobb 500 broiler breeders during the first year of reproduction. The research material was hatching eggs (280 pcs), whose quality was assessed 7 times in the reproductive season at 5-week intervals. The eggs were examined when the hens were aged 26, 31, 36, 41, 46, 51 and 56 weeks (40 eggs for each age). The following characteristics were evaluated: egg weight (g); egg shape index (%); egg specific gravity (g/cm3); shell thickness (mm); average number of pores in the eggshell (pcs/0.25 cm2); yolk, white and shell weight (g) and their percentage in the egg mass; yolk index (%) and the number of Haugh units. The investigations proved that as the reproductive season of hens progressed, the weight of their eggs increased. Above all, this was due to the increase in the yolk weight, because its percentage in the egg weight rose with bird age, whereas the percentage of the white decreased. However, as the reproductive season progressed the quality of both the yolk and white deteriorated. No negative relationship between the age of hens and shell quality (weight, thickness) was observed. Only when the birds were aged 56 weeks, the shell thickness was found to be significantly smaller.