The variation in amino acid levels in the blood plasma of breeding roosters during sexual maturation*

Abstract. The paper provides an overview of results obtained in the study of variation in free amino acid levels in the blood plasma of breeding roosters (RIR 05 line) during sexual maturation (in the 10th, 15th, 20th and 25th weeks of age). The results prove that dynamic changes in free amino acid concentrations in blood plasma are connected with the sexual maturation of breeding roosters. During this period the concentrations of each particular free amino acid varied at a significance level of P ≤ 0.05 and P ≤ 0.01. Furthermore, in most cases the plasma concentrations of free amino acids in the 10th and 15th week were higher in comparison with those in the 20th and 25th week. Interestingly, the concentrations of individual free amino acids ranged over a wide interval (units, tens and hundreds of μmol/l). In this respect the free amino acids in plasma can be divided into three groups. The first group consisted of amino acids that occurred at low molar concentration (up to 100 μmol/l): cysteic acid, aspartic acid, α-aminoadipic acid, methionine, isoleucine, γ-aminobutyric acid, 3-methylhistidine, tryptophan and ornitine. The second group included amino acids occurring at medium to high molar concentration (100–300 μmol/l): taurine, glutamine, 1/2 cystine, valine, leucine, tyrosine, phenylalanine, histidine, lysine and arginine. Finally, the third group contained threonine, serine, glutamic acid, proline, glycine and alanine that were present at high molar concentrations (above 300 μmol/l). Analyses of plasma in the period from the 10th to 25th week detected dynamic changes in levels of individual free amino acids and showed that the total content of these amino acids gradually decreased to the following mean values: 5 685.00 μmol/l in the 10th week, 5 076.21 μmol/l in the 15th week, 4 384.78 μmol/l in the 20th week and 4 793.30 μmol/l in the 25th week.