One-hundred-eighty fatteners of both sexes (body mass 2830 kg) were fed according to the Polish and German stds. and with a feed of decreased content of crude proteins (by 10%) optionally supplemented with synthetic lysine and methionine (with cysteine) to compare the emission of N compds. in excrements to the environment. The decrease in protein content resulted in a reduction of the daily gain of the body mass in the whole population but also in decrease of N compd. emissions. The addn. of diet supplements did not show any significant effect on the emission of N compds.