Protein content and amino acid concentrations in M-longissimus dorsi of lambs of various genotypes

The objective of a trial was to study the effect of breed on protein content and their amino acid composition in M. longissimus dorsi of lambs of inland sheep breeds: Tsigai, Merino and Improved Wallachian. The lambs had free choice of feed mix VJ (for lamb production) to the live weight of 35.0 kg. Eight ram-lambs of each breed were slaughtered when they reached this weight. M. longissimus dorsi was prepared from warm carcasses. Total protein content was determined by Kjeldahl method. Amino acid concentrations were determined after acid hydrolysis of proteins by ion exchange chromatography on an amino acid analyzer T 339. Data were subjected to statistical processing by F-test and interbreed differences were assessed by t-test. Tabs. I to III show the results of the trial. Total protein content (Tab. I) ranged from 20.66 to 20.90%, without any statistically significant differences. Improved Wallachian lambs had the lowest content of amino acids (75.77 g/16 g N), the difference was statistically significant (P < 0.05) in comparison with the other two genotypes. But this breed had high contents of essential amino acids out of total amino acids (38.11%). The differences in amino acid concentrations between the lambs of Tsigai and Merino breeds were negligible (83.99 and/or 84.62 g/16 g N), while Tsigai lambs had the highest content of essential amino acids (32.43 g/16 g N). Lambs of the Merino breed had the worst content of essential amino acids out of their total (37.41%), which made them statistically significantly different from Tsigai breed (P < 0.01). Statistically significant interbreed differences applied to all essential amino acids except lysine (Tab. II), which showed the highest content out of the essential amino acids (7.45-8.14 g/16 g N). There were also large, statistically significant differences in the content of nonessential amino acids (Tab. III). The largest differences were determined for proline (2.65-4.50 g/16 g N), where the values were statistically significant in all three breeds concerned. Only tyrosine and histidine contents exhibited insignificant differences. The highest content out of all amino acids was recorded for glutamic acid (11.70-13.24 g/16 g N). The results confirm the effect of breed on amino acid composition of M. longissimus dorsi of lambs.