Performance of growing pullets and laying hens fed low-protein, amino acid-supplemented diets

An experiment was conducted to determine the effect of feeding low-protein, amino acid-supplemented diets during growing and laying periods on performance of a commercial strain of White Leghorn chickens. The birds of the positive control were fed diets in a sequence of 20, 16, and 14% protein during 0 to 6, 6 to 12, and 12 to 18 wk (growing period) and of 18, 16.5 and 15% protein during 18 to 34, 34 to 50, and 50 to 66 wk of age (laying period). The birds of the negative control were fed protein levels of 16, 13.5, and 11.5% in the growing period and 14, 13, and 12% in the laying period. Other groups were fed the negative control series supplemented with methionine, methionine plus lysine, or methionine plus lysine plus other deficient essential amino acids. An additional group was fed the negative control supplemented with methionine plus lysine during the growing period and a protein sequence of 15, 14, and 13% supplemented with methionine and lysine during the laying period. At 18 wk of age, birds fed the negative control supplemented with methionine plus lysine or methionine plus lysine plus other deficient essential amino acids had comparable body weight to those fed the positive control despite significantly lower protein and lysine intake. Overall egg production and egg weight of birds fed the sequence of 14, 13, and 12% protein supplemented with combination of methionine, lysine, and extra levels of tryptophan and isoleucine or of the birds fed the sequence of 15, 14, and 13% protein supplemented with methionine and lysine were not different from those fed the positive control. However, egg mass and body weight were inferior to those of birds fed the positive control.