ABSTRACT Besides the immunological benefits of colostrum consumption, this lacteal secretion has a great concentration of biological molecules that can affect gut physiology and fish healthy. This study evaluated the antioxidant potential in the gut of juvenile pacu, Piaractus mesopotamicus, and dourado, Salminus brasiliensis, fed twice a day with diets containing 0, 10 or 20% of lyophilized bovine colostrum (LBC). The whole medium and posterior intestine was collected after 30 or 60 experimental days and the activity of catalase, superoxide dismutase and glutathione peroxidase was determined as one international unit per milligram of protein, and the oxygen radical absorbance capacity as μM of equivalent Trolox per milligram of protein. Only the juvenile pacu were affected by the diet containing LBC (P < 0.05). The juvenile fed 10% LBC showed higher oxygen absorbance capacity than the juveniles fed 20% LBC (P < 0.05). Interaction between diet and period was observed to superoxide dismutase (SOD) activity (P < 0.05), juvenile pacu fed 0% LBC and 10% LBC did not change enzyme activity at 30 and 60 days, whereas juvenile fed 20% LBC showed higher value at 60 days compared to 30 days (P < 0.05). The present result reveal that the consumption of diet containing LBC improved SOD activity in the gut of juvenile pacu indicating a possible protective action of this lacteal secretion in an omnivorous fish.