NITROGEN-BALANCE IN GROWING PIGS AT VARIOUS PROTEIN AND AMINO-ACIDS LEVELS

The nitrogen balance was assessed in the metabolic experiment with eight pigs of higher genotype (Seghers Hybrid) of average weight of 43 kg in four balance periods with four levels of crude protein and amino acids using the isoenergetic mixtures. The average nitrogen and lysine intakes in groups I to IV were 36.0, 37.6, 40.2 and 42.4, and 10.4, 12.6, 14.3 and 15.7 g per animal and day, respectively. Nitrogen digestibility amounted to 81.38, 82.46, 83.07 and 83.84% in this sequence. From the nitrogen ingested, 46.36, 50.83, 51.29 and 54.23% were deposited. The differences in values between groups I and IV were significant in both cases (P < 0.05). Pigs in experimental groups I to IV deposited 104.2, 119.4, 128.8 and 143.7 g of crude protein daily, the difference between the values in groups I and IV was significant (P < 0.05) (Tab. V). All pigs ingested in average 18.3 MJ of metabolizable energy per animal and day. The obtained results give evidence for the ability of pigs of the genotype employed to deposit a comparatively large amount of crude protein daily although the crude protein and lysine intake did not reach the maximum level of crude protein retention in the body. An increased ingestion of lysine affected positively not only the level of crude protein deposition but their digestibility as well.