PL
Badano wpływ nawożenia azotowego (0, 60 i 120 kg N/ha) na skład chemiczny i aminokwasowy ziarna ozimych odmian pszenżyta, pszenicy i żyta. Na rosnących szczurach, żywionych mieszankami ziarna zbóż z uzupełniającą śrutą sojową (białko zbóż : białko śruty = 1 :1), przeprowadzono ocenę wskaźników jakości białka (BV, TD i NPU). Nawożenie azotowe podnosiło zawartość białka ogólnego i obniżało względną zawartość lizyny w białku ziarna. Obniżeniu ulegały także wskaźniki jakości białka mieszanek zbożowo-sojowych.
EN
The effect of N fertilization levels (0, 60, and 120 kg N/ha) on chemical composition and amino acid content in winter triticale, wheat and rye grain was studied. Separate estimates of biological value (BV), true digestibility (TD) and net protein utilization (NPU) were obtained on growing rats fed diets containing 10% protein, originating from grain (5%) and soya bean (5%). The N fertilization increased grain protein content (%) and decreased (r = -0.35) relative lysine content (g/16 g N), whereas lysine content expressed in terms of g/kg grain was increased (r = + 0.39). The amino acid composition of grain cultivars compared to the egg reference protein identified lysine as the first limiting amino acid (CS = 45), and isoleucine as the second. In contrast, the chemical score determined for grain-soya bean mixtures identified sulphur amino acids as the limiting ones, and its value was improved (CS = 54), thus indicating a complementary effect of supplemental soya bean. The grain obtained from increasing N fertilization levels, fed in grain-soya bean mixtures to rats, tended to reduce the BV and to increase the TD. It was insufficient to prevent the fall in the NPU of the proteins. In contrast to what was expected, the BV values were significantly (P) correlated (r = + 0.44) with the lysine content of the mixtures. Negative nutritional effects resulting from high N fertilization of cereals are discussed.