The excretion of free amino acids by laying hens was measured during the period 0 to 5 h after the oral administration of 0.1 g lysine HCl or 0.1 g arginine HCl. Lysine administration resulted in a significant increase in the excretion (μmoles) of arginine (6.8 to 25.9), ornithine (5.8 to 39.3) and tyrosine (3.2 to 5.1) while arginine administration resulted in a significant increase in the excretion (μmoles) of lysine (6.8 to 93.0), ornithine (4.1 to 71.9), tyrosine (2.3 to 5.5), histidine (10.8 to 88.3), threonine (16.8 to 33.3), serine (22.7 to 34.0) and glycine (17.3 to 56.3). The effect of arginine administration on lysine excretion was significantly greater than that of lysine on arginine excretion (P < 0.01). In the lysine experiment the overall pattern of changes in the hourly excretion rate of the affected amino acids was the same as that of administered lysine. The maximum hourly excretion rate of administered arginine occurred one hour earlier than the maximum for the amino acids affected by administered arginine. It is suggested that arginine may alleviate certain dietary amino acid excesses by increasing the excretion of that amino acid which is in excess. |