H. Lukanov

Abstract. Egg quality traits have been investigated in chickens from different production types, namely egg-laying breeds or breeds interesting from the point of view of genetic diversity maintenance. In this research, studied eggs were produced by 50-week-old layers from the following breeds: Rhode Island Red, Rhode Island White, Starozagorska Red, Schijndelaar, White Leghorn and Black Shumen chicken. The studied egg traits were egg weight (g), egg shape index, albumen index, Haugh units, yolk index, yolk colour (Roche), eggshell weight (g) and average eggshell thickness (μm). Among the tested breeds, the eggs of Rhode Island White line D were with the highest weight: 63.3±0.77 g. White Leghorn eggs were with the highest albumen index: 9.07±0.23 and Haugh units: 83.13±0.98. The greatest eggshell thickness had eggs of Rhode Island White line D (422.98±6.26 μm).