The advantages of Legart geese cause a fairly wide demand and their rapid distribution in the country's farms, however, geese of this breed are quite sensitive to unbalanced feed, especially in the first weeks of life. Understanding the mechanisms of the formation of adaptive responses to a damaging effect contribute to the right choice of a strategy aimed at regulating the state of the redox system of the bird’s body and revealing the genetic potential of this breed’s productivity. The purpose of the research is to elucidate the features of supporting the prooxidantantioxidant balance in the tissues of Legart geese during embryonic and early postnatal development. The specifics of maintaining the balance between pro- and antioxidants in the tissues of the heart and brain of geese of this breed is investigated. It has been proved that activation of the antioxidant system in the brain is genetically programmed, aimed at adapting the geese organism to hyperoxia of the onset of atmospheric respiration by increasing the activity of antioxidant enzymes and reducing the content of unsaturated fatty acids. In the myocardium, maintaining equilibrium occurs mainly due to the activation of the enzymatic component of the system. However, taking into account the opposite changes in the coefficient of antioxidant activity and the activity of antioxidant enzymes, on the one hand, and on the other, a stably high content of unsaturated fatty acids, it is in the myocardium that there is a very high probability of implementing of alternative mechanisms of antioxidant defense
geese, Legart, ontogenesis, brain, myocardium, antioxidant defense system