EFFECT OF DIETS WITH LOW-PROTEIN CONTENT AND SUPPLEMENTED WITH AMINO-ACIDS ON EGG-PRODUCTION AND NITROGEN-EXCRETION EXCRETION OF LAYING HENS

For 36 weeks (26. to 62. week of production) 4 diets with crude protei n contents of 17 %, 15 %, 13 % or 11 % were given to 9 hens each. Food intake was limited to 115 g/day and hen, the hens were kept singly in battery cages. Diets were supplemented with synthetic amino acids to ensure that the supply of essential amino acids in every experimental treatment was at least as high as the NRC's (1984) recommendations. Eg g production, feed conversion, development of bodymass of hens and nit rogen-balance showed, that 17 % and 15 % protein in the diet equally a llowed high performance (egg production about 85 % and egg weight abou t 63 g) while 13 % and 11 % protein in the diet did not meet the requi rement and by this lowered production. An effect of the low concentrat ions of some essential amino acids in these 2 diets on performance can not be excluded. Compared to 17 % crude protein nitrogen excretion pe r animal and nitrogen excretion per gram egg mass could be reduced by 20 %, 33 % and 48 % respectively and by 12 %, 21 % and 29 % respective ly when protein content of the diet was lowered to 15 %, 13 % and 11 % respectively.