THE NUTRITIONAL-VALUE OF HIGH-LYSINE BARLEY DETERMINED IN RATS, YOUNG-PIGS AND GROWING PIGS

Three experiments, the first with rats, the second with young pigs and the third with growing pigs, were carried out to compare the nutritio nal value of cv Lysimax, a newly developed high-lysine barley, to cv L ami, a conventional barley grown in Denmark. In the diets for rats and growing pigs the barleys were the sole protein source while in the ex periment with young pigs the barleys made up to 649 g kg(-1) of the re spective diets. The lysine content of cv Lysimax was 52.6% higher than that of cv Lami; 4.99 g 16 g N-1 compared to 3.27 g 16 g N-1. The con tents of threonine, tryptophane, methionine and cystine of cv Lysimax were 3.80, 1.41, 1.80 and 2.27 g 16 g N-1, respectively; being 18.4, 8 .5, 9.8 and 5.1% higher than in cv Lami. Conversely, the contents of g lutamic acid and proline in cv Lysimax were 15.79 and 7.40 g 16 g N-1, respectively, being 36.1 and 40.0% lower than in cv Lami. In the expe riment with rats, the higher lysine content and the lower content of g lutamic acid and proline in cv Lysimax resulted in a 34.8% increase (P < 0.05) in biological value (BV); 0.867 for cv Lysimax compared to 0. 643 for cv Lami. True protein digestibilities and energy digestibiliti es in rats fed cv Lysimax were 0.019 and 0.010 units lower (P < 0.05) than for cv Lami. For young pigs the increased lysine content and the lower content of glutamic acid and proline of cv Lysimax increased (P < 0.05) nitrogen (N) retention from 10.9 to 12.4 g day(-1), respective ly, and increased (P < 0.05) apparent BV from 0.690 to 0.734, respecti vely. The digestibility of energy was 0.030 units lower (P < 0.05) for the diets with cv Lysimax than for the diets with cv Lami. Likewise, with growing pigs the increased lysine content and the lower content o f glutamic acid and proline increased (P < 0.05) N retention from 6.4 to 10.8 g day(-1) and apparent BV from 0.271 to 0.495, respectively. T he apparent ileal digestibilities of lysine, threonine, tryptophane, m ethionine and cystine were similar (P > 0.05) between the barleys. It is concluded that the development of high-lysine barley varieties coul d be beneficial for meeting the requirements of essential amino acids for monogastrics. Moreover, N excretion into the environment was subst antially reduced due a reduction in the prolamine fraction which is ri ch in glutamic acid and proline.