The beta-lysine activity of blood serum and egg white in broilers and broiler breeders from the ROSS 308 hybrid reared in industrial conditions was studied using a photometric method. The birds from the experimental groups were treated with polybacterial immunomodulator "AVIGEN", the anti-stress preparation "ASPIVIT C" and the preparation "BIOXAN", which helps to increase the resorption surface of the intestinal mucosa.We found increased activity of beta-lysine in the blood serum in immunomodulator-treated broilers. No significant differences were found in the activity of beta-lysine in the blood serum of the experimental and control parent herds until the onset of lay. On the onset of lay, we observed an increase in beta-lysine activity in the blood serum, especially pronounced in the experimental herd. We also registered an increase in this indicator in the egg white of the birds from the experimental flock from the 2nd to the 7th day after laying. Elevated serum beta-lysine concentrations during the onset of lay, legitimizes beta-lysine as a stress-induced factor of non-specific immunity. The higher levels of beta-lysine in the blood serum and egg white of the experimental herds are probably due to the stimulation on the mucous membranes with the polybacterial immunomodulator AVIGEN.