Male broiler performance during the starting and growing periods as affected by dietary protein, essential amino acids, and potassium levels.

Three experiments were conducted to determine the effects of dietary CP, essential amino acid (EAA), and K content upon male broiler performance during starting and growing periods (7 to 21 and 21 to 42 days, respectively). In Experiment 1, five grower diets formulated to be equal in K content and containing the following analyzed CP contents were used: 21.9, 19.1, and 16.2% with and without L-glutamic acid (GLU) supplementation or 10% increased levels of arginine (ARG), threonine (THR), isoleucine (ILE), and tryptophan (TRP). Seven diets containing the following analyzed CP contents were fed in Experiment 2: 21.5%, 19.6% with and without K supplementation, and 16.0% with and without K supplementation and/or 10% increased levels of ARG, THR, ILE, and TRP. In Experiment 3, four starter diets containing the following CP contents were fed: 24.5%, and 17.8% without and with added K. In all three experiments feed efficiency (FE) was lower and in Experiments 1 and 2, abdominal fat deposition (AFD) was higher with lower levels of dietary CP. Lower body weight gains (BWG) occurred with lower levels of dietary CP in Experiments 2 and 3, but not in Experiment 1. Adding extra ARG, THR, ILE, and TRP to the lowest CP diet sometimes improved FE, but had no effect on BWG or AFD. Supplementation with GLU or K failed to influence BWG or FE. However, addition of GLU was associated with lower AFD. Maximal performance generally was not obtained with the low CP, amino acid-fortified diets.