The use of biological products ecologically safe for human and animals is the key to improve the quality of life. The replacement of synthetic antibiotics, hormone stimulants and other hazardous chemical drugs by natural substances of plant origin is an effective step to decrease gastrointestinal disorders and to improve the indices of growth and development of various species of animals. The beneficial effect of the above drugs can be explained by the potential of these substances to maintain beneficial microflora of gastrointestinal tract that protects the animal from pathogenic bacteria and softens the course of stressful periods. The article presents the data on the research of the state of antioxidant system of ducks when the antihelmintic drug phenbendazol and Macleay cordata were used separately and in the combination. The experiments have shown that the use of only phenbendazole for ducks led to the activation of the processes of lipid peroxidation that was manifested by the decrease in the activity of catalase and superoxide dismutase (SOD) as well as antioxidant activity (AOA) of blood that proves the lack of the potential of own resources of antioxidant system (AOS) in the experimental birds. The addition of the herbal supplement of Macleay cordata separately and simultaneously with phenbendazole resulted in the induction of antioxidant resources in the body of the examined ducks that was characterizes in the first case by the storage of the levels of LPO products due to the induced activation of both antioxidant enzymes and the restoration of the pool of the endogenous total AOA, and in the second case, by the reduction to the normal physiological activity of catalase and compensatory increase in the activity of SOD alongside with the increase in the total antioxidant activity.