The nutritional value of new high-lysine barley varieties determined with rats and young pigs

Abstract

Three experiments were conducted to evaluate the nutritive value of four new high-lysine barley mutants, their parent variety Sultan and the high-lysine variety Lysimax. The problem of low yield, frequently encountered in previous studies with high-lysine barley, was overcome for Lysimax in this study; cv. Lysimax yielded 4% more than cv. Sultan. The highest lysine levels: 4.87, 4.75 and 3.96 g 16 g−1 N occurred in cv. Lysimax and Risø mutants (RM) 609 and 1405 compared with 3.48, 3.43 and 3.55 g 16 g−1 N in cv. Sultan and RM 1242 and 1385, respectively. Compared with cv. Sultan, the glutamic acid levels in RM 1405 and 609 and cv. Lysimax were 7.2, 25.8 and 31.3% lower, respectively. Likewise, the proline levels in RM 1405 and 609 and cv. Lysimax were 10.3, 32.2 and 37.9% lower, respectively. In the first experiment, with rats, the barleys were the sole protein sources in the diets. In the second experiment, with young pigs, only cv. Lysimax and RM 1405 were used (700 g kg−1 diet) in two starter diets. In the third experiment, the diets fed to the pigs in the second experiment were diluted with an N-free mixture and fed to rats. In the first experiment, biological values (BV) of cv. Lysimax and RM 609 (89.0% and 91.0%, respectively) were significantly greater than that of cv. Sultan (73.9%). Compared with Sultan true protein digestiblities (TD) and energy digestibility (ED) were slightly lower (P < 0.05), at most 3.6 and 4.2 percentage units, in RM 609, 1385 and 1405 and cv. Lysimax, respectively. In the second experiment with young pigs, the apparent BV of the Lysimax diet (84.1%) was higher (P < 0.05) than that of the RM 1405 diet (77.4%). The ED was 2.1 percentage units lower (P < 0.05) for the Lysimax diet than for the RM 1405 diet. In the third experiment with rats, the BV for the Lysimax diet was higher (P < 0.05) than for the RM 1405 diets, TD and ED were similar (P > 0.05). It is concluded that the development of high-lysine barley varieties is beneficial for meeting the requirements of indispensable amino acids for monogastric animals. Moreover, N excretion into the environment is substantially reduced due to a reduction in the prolamin protein fraction which is rich in glutamic acid and proline. Key words: Rats, pigs, barley, amino acids, digestibility