Effect of laying period and duck origin on egg characteristics

Abstract. The study was carried out on eggs of two-year-old Orpington ducks (O1) and crossbred ducks Khaki Campbell×Orpington (KhO). Eggs for analysis were collected in the 6th and the 22nd week of egg laying. The eggs of KhO ducks had greater weight (72.45 g), specific gravity (1.083 g/cm3) and a thicker shell (0.67 mm) in comparison to eggs of the O1 population (70.64 g, 1.081 g/cm3 and 0.65 mm, respectively). Eggshell content accounted for 9.53% and 7.85% of egg weight in KhO and O1 ducks, respectively. Eggs of KhO ducks were characterized by a lower egg white index (0.07), yolk content (39.48%) and protein content of egg white as well as lower L* parameter of yolk than eggs of O1 ducks. In KhO eggs, yolk lipids contained more C 18:1 cis-9, C 20:4, C 22:6 and C 20:5 and less α C 18:3 and C 18:1 trans-11 fatty acids than those of O1 eggs. The eggs laid in the 6th week had greater weight (by 3.61 g), specific gravity (by 0.01 g/cm3), egg white content (by 2.26%), eggshell thickness (by 0.04 mm), strength (by 10.70 N) and deformation (by 0.90%), and lower yolk content (by 2.34%) than the eggs laid in the 22nd week of laying. Furthermore, the eggs laid at the beginning of the second laying period were characterized by higher protein content of egg white and yolk (by 0.26% and 0.49% respectively) and pH value of egg white and yolk, lower lightness of yolk (L*), higher unsaturated fatty acids (UFA) content of yolk (especially polyunsaturated fatty acids – PUFA, by 2.53%), and lower saturated fatty acids (SFA) content of yolk (by 3.10%) and total cholesterol content (by 2.38%).