Abstract. A total of 60 drakes out of three flocks of conservative Miniduck (K2), Polish Pekin (P33), native Pekin population type A3 and two breeding strains (A55, P66), aged seven weeks, were used for comparison. The content of protein, lipids, moisture, essential amino acids, fatty acids and cholesterol were estimated. There were differences among flocks in all biochemical parameters. The muscles of A55 and P66 comprised more protein and less moisture than P33 and A3 muscles. The P33 breast muscles comprised the least of lipids (0.8% v/s 1.16–1.32%), however A55 of cholesterol (71.21mg/100g v/s 82.23–111.82 mg/100g). The isoleucine (ILE) and valine (VAL) were amino acids which limited the biological value of meat proteins from breast muscles of A3, P33 and K2, however tryptophan (TRP) for A55, P66 muscles. The unsaturated fatty acids (UFA) were predominant for all flocks (50.12–60.64%), the P66 muscles contained the most of UFA and P33 the most of saturated fatty acids (SFA). The highest level of polyunsaturated fatty acids (PUFA) was established in K2 muscles. The PUFA/SFA and n-6/n-3 PUFA ratios were 0.63–0.84 and 3.22–5.85 respectively. The lipids of A55 were characterized by the best fatty acid profile among the investigated muscles. Taking into consideration the nutritive value of proteins, cholesterol content and profile of fatty acids, A55 breast muscles appeared to be the most favourable from the human health point of view.

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Compared with strain A44, male and female ducks of strain A55 showed significantly higher body weights at 7 weeks of rearing. They did not differ only in shank length and breast muscle thickness. Dressing percentage and percentage of tissue components were similar in both strains. Only the percentage of skin with subcutaneous fat and weight of abdominal fat were lower in A55, which is a favourable result. The weights of breast and leg muscles were found to be positively and significantly correlated with the lengths of trunk with neck, trunk, sternum and shank. The percentage of skin with subcutaneous fat combined with abdominal fat was significantly and negatively correlated with trunk and sternum length and with chest and shank circumference. Trunk and sternum length can be used in selection for high weight of breast and leg muscles and decreased fatness, while shank length can be employed in the selection for decreased fatness. pH 15 and pH 24 values in strains A44 and A55 were similar to those found in other studies. The water holding capacity of breast and leg muscles was high and higher in A55, whereas the water content of muscles was similar in both strains. Percentages of protein and ash were higher in breast muscles and those of fat in leg muscles. In other Polish and foreign studies the proportions of protein, fat and ash in the muscles were greater. The meat quality of A55 ducks was superior to that of A44 ducks.

In two Polish conservative flocks of Miniduck (K2) and Pekin (P33), registered by FAO as domestic genetic resources (World Watch List, 2000) the mean values of physical (tissue components) and qualitative traits of meat (pH 15 , pH 24 , colour of meat) were determined. The experimental flocks showed significant variations in body weight at 7 weeks of age (1540 vs 2088 in drakes and 1395 vs 1986 g in ducks), in the proportion of breast and leg muscles and skin with subcutaneous fat in eviscerated carcass. K2 ducks are characterized by outstanding musculature of breast and P33 ducks by that of lower leg and by low fatness. pH 15 values of breast and leg muscles in K2 and P33 birds were greater than pH 24 of these muscles. In both flocks pH 15 values of 6.09 to 6.33 and pH 24 values of 5.90 to 6.05 in breast muscles were lower than in leg muscles (6.33 to 6.46 and 6.12 to 6.37, respectively). A significantly lower L* value (darker colour) of breast muscle was characteristic of K2 birds (43.7 in males and 40.5 in females) compared to P33 males and females. Furthermore, breast muscles of K2 drakes and ducks had significantly higher redness (a*) and yellowness values (b*) than P33. In pectoralis superficialis muscle of K2 and P33 females, a significantly lower diameter was found for white muscle fibres (αW) (30.0 to 30.5 µm) and for red muscle fibres (βR) (16.9 to 17.6 µm) than in biceps femoris muscle (αW from 48.3 to 54.2; βR from 36.0 to 37.1 µm). Muscle fibres of K2 compared to P33 ducks were characterized by significantly greater diameters of βR muscle fibre in pectoralis superficialis muscle, and by lower αW and βR fibre diameters in biceps femoris muscle. The experiment showed that meat of ducks from the conservative flocks studied is valuable from the consumer's point of view.

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%).