Dry matter (DM), crude protein (CP), and the content of individual amino acids (AA) were determined in the bodies of Ross 308 and Cobb 500 hybrids including feathers after 40 days of fattening. Percentages for the content of individual AA were then calculated from the total sums of AA. The level of CP, irrespective of sex, was 453.16 ± 5.916 g/kg of DM for the Ross and 470.94 ± 5.404 g/kg of DM for the Cobb hybrid (P ≤ 0.05). For both hybrids, the content of CP was significantly (P ≤ 0.01) higher for cocks as opposed to hens. The AA levels in DM, irrespective of sex, were higher in the Cobb hybrid except for Glu; it was significantly higher for Asp, Ser, Ala, Lys (P ≤ 0.01), and Thr and Arg (P ≤ 0.05). The values for the majority of AA were higher for cocks than for hens in both hybrids. For the majority of essential AA, significant (P ≤ 0.01; P ≤ 0.05) differences were recorded between sexes. For non-essential AA except for Ser and Ala, significantly (P ≤ 0.01; P ≤ 0.05) higher values were found in cocks. Of the total sums of AA in DM of Ross broilers, the largest presence (here and after in %) was that of Glu (14.92), followed by Leu (8.80), Asp (8.73), Gly (8.71), Arg (7.21), Val (6.33), and Pro (6.09). The lowest contents were those of Met (2.41) and His (3.28). For the Cobb hybrid, the AA were Glu (13.90), Asp (9.12), Gly (8.48), Leu (8.43), Arg (7.48), Lys (6.44), and Pro (6.09). The AA lowest contents were those of Met (2.30) and His (3.16).
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