Effects of breed, hen age, and egg storage on the indirect prediction of the albumen quality

Abstract

Albumen quality (Haugh unit score) was indirectly estimated by the Narushin-Morgun's non-destructive method based on measuring egg specific gravity, weight, length, and width, and the previous estimation of shell weight. A total of 4,201 eggs were obtained from hens of different breeds of Spanish chickens, i.e.;Castellana, Andaluza, Menorca (white egg layers); Prat, Leonesa (tinted egg layers); Vasca, Villafranquina (brown egg layers); an F2 synthetic breed; a White Leghorn population, and the ey tester line. Samples were obtained from two groups of hens (at 28-32 wk and 50-54 wk of age), and two groups of eggs (fresh or stored at 15 °C for 1 d). Differences among breeds for egg specific gravity were significant (P < 0.001); all values were higher than 1.084 /cm3, tinted egg breeds ranking before the white and brown egg breeds. Storage of eggs was a more important source of variation on specific gravity than age of hen; a short storage at 15 °C for 1 d produced a significant decrease in this trait. Although eggs laid by hens of second age had statistically significant lower specific gravity than those laid by hens of first age, this difference was slight and without practical significance. Mean values for shell weight reflected the fact that large and thick eggs have generally heavier shells than small and thin eggs, those from hens at 50-54 wk of age or freshly sampled having a higher shell weight. Haugh unit scores were clearly underestimated in all breeds, mean values ranging approximately from 60 to 70 units, with respect to those calculated directly in eggs from Spanish breeds which had been stored for 1 d (albumen quality ranging from 80 to 90 units in this case). There were no significant differences among white, tinted, or brown eggs. There were unexpected increases for the indirect estimate of Haugh unit score in hens of second age, and unexpected no changes after storage for 1d. The results suggest that the non-destructive method for indirectly measuring the Haugh unit score might have no practical value, and although it may be a suitable method to analyse genetic differences among breeds, comparisons between different hen ages or egg storage lengths might not be possible.