The analysis of slaughter yield and meat quality was performed on a total number of 96 birds from four medium-heavy weight pedigree strains. Based on their strain, cockerels were divided into the following groups: group I - strain N88 (originating from New Hampshire), group II - strain R55 (Rhode Island Red), group III - strain S11 (Sussex) and group IV - strain P55 (Plymouth Rock). Each group consisted of 24 birds. At 12 weeks of age, half of the cockerels from each group was caponised. In

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... l, 48 birds were caponised (12 birds in each strain). Based on the strain, capons were then divided into groups V (N88), VI (R55), VII (S11) and VIII (P55). It was noted that the strain and caponisation had influence on differences in such traits as the weight of eviscerated carcass with neck and slaughter yield. On the other hand, it was observed that caponisation did not affect significantly the total weight, percentage share of breast and drumstick muscles in carcasses of birds from analysed strains. No significant differences were observed between groups in terms of physicochemical properties of meat. The highest content of water in breast and drumstick muscles was observed among cockerels and capons from strain N88 (groups I and V). Protein content in cockerels' breast muscles differed depending on their strain whilst among capons (groups V-VIII) it was similar. It was also noted that capons originating from strains S11 (VII) and P55 (VIII) stood out significantly with higher fat content in breast muscles compared to cockerels from the same strain (groups III and IV). The effect of caponisation on higher fat content in drumstick muscles was confirmed in all observed groups. Capons from all strains had more fat in drumstick muscles compared to cockerels of the same origin.