The results of research on the effectiveness of multicomponent feed additives based on plant substances as an alternative to antibiotics are presented. It has been observed that prebiotics improve animal health and productivity and increase the efficiency of the production process. At the same time, separate feeding of prebiotics is less effective compared to the use of a complex of substances of different functional purpose. Effect of the organomineral feed additive with and without lactulose on morpho-biochemical composition of blood, digestibility of diet components and productivity of broiler chickens has been evaluated. Three groups (n = 90) were formed for the experiment: the 1st experimental group in addition to the main diet received a complex organomineral feed additive, starting from 7-day-old until the end of the experiment (42-day-old); the 2nd group received the same additive without lactulose. The control group received the standard basic diet. The positive effect of organomineral additive on the productive parameters of broiler chickens was established, to a greater extent in the presence of lactulose. The content of albumin and total protein in the blood of broiler chickens was positively correlated with the growth rate in the animals. Higher concentration of these indices in the group with lactulose may contribute to enhanced growth rate in the experimental animals. The 1st experimental group showed an increase in the live weight gain by the end of the study by 17.9%, while in the 2nd group it was 10.8%. Also, with the diet containing lactulose, the indices of nutrient digestibility increased by the end of the study by 3.8–4.7% compared to the control. The use of the organomineral feed additive in the feeding of broiler chickens is a promising approach.