The use of low-protein, low-phosphorus, amino acid- and phytase-supplemented diets on laying hen performance and nitrogen and phosphorus excretion.

Two experiments were conducted to determine whether, by using a low-protein, amino acid-supplemented diet or a low-protein, amino acid-supplemented diet in conjunction with low-P, phytase-supplemented diet, the excretion of N and P could be reduced without affecting the productive performance of laying hens. Eight dietary treatments were assigned to Babcock B300 hens in each of 2 experiments that involved a positive control (16 to 16.5% CP) and a negative control (13% CP) with and without supplementation with the limiting essential amino acids. In experiment 1, supplementing the negative control with lysine, methionine, and tryptophan resulted in performance comparable to that obtained with the positive control, with the exception that egg weight was heavier for the negative control supplemented with amino acids. Supplementing the negative control with additional essential amino acids improved the performance higher than the positive control indicating that the positive control was deficient in one or more essential amino acids. In experiment 2, supplementing the negative control containing 0.2% nonphytate P (NPP) with all the limiting amino acids plus phytase resulted in performance comparable to the positive control group, which was fed 0.4% NPP without phytase. The results of a digestibility assay indicated that daily total P and N excretions of the negative control containing 0.2% NPP and supplemented with limiting amino acids and phytase were reduced by 48 and 45% of the positive control group, respectively, without compromising laying performance.