Egg shell quality in some white-egged and brown-egged cross combinations of dominant hens

Egg shell quality is one of the most important parameters of technological value of eggs because it influences the economics of egg production to a gr eat extent. The goal of trials was to examine egg shell quality in nine whi te-egged lines of White Leghorn (025, 026, 028, 031, 032, 033, 036, 038, 03 9) and in brown-egged final hybrid D 102, which were all selected on a bree ding and reproduction farm for Dominant poultry at Dobrenice in the Czech R epublic. Laying hens received a common commercial mixture with 14.49% of pr otein. Egg shell quality was examined between weeks 20 and 44 of layer age and egg analyses were conducted in 28-day intervals. The significantly high est egg weight was determined in brown-egged hybrid D 102 (64.09 g, P less than or equal to 0.05) and in white-egged line 033 (63.85 g, P less than or equal to 0.05). White-egged line 033 had the highest shell weight (7.21 g, P less than or equal to 0.05). There were no significant differences betwe en the genotypes in the values of shell weight to egg weight ratio while th e highest shell proportion was determined in lines 031 and 032 - 11.37% and 11.34%, respectively. The significantly highest shell thickness (0.37 mm, P less than or equal to 0.05) was observed in line 038 and in brown-egged h ybrid D 102. Line 038 had the significantly highest shell strength, which w as confirmed by a nondestructive method because the shell deformation was l owest in line 038 - 34.80 mu m (P less than or equal to 0.05).