Daily oxygen supplementation to the incubator at different stages of embryonic development alters the activity of antioxidant enzymes in the lung tissue of broiler chicks at a high altitude.

1. Pulmonary hypertension, associated with mitochondrial function in the lung tissue of broilers, can occur at hypoxic high altitudes. The present research examined the impacts of O supplementation at different embryonic stages on broiler organ development and antioxidant enzyme activities.2. In total, 360 eggs from Ross 308 broiler breeders at sea level were divided into a control group (O non-supplementation group) and three experimental groups daily 1 h 23.5% O supplementation from days 0 to 11 (O), from days 12 to 21 (O), and from days 18 to 21 (O) of embryonic age.3. The lung, heart, right ventricular (RV), and left ventricular (LV) + septum of newly hatched and seven day old chicks from every group were dissected and weighed. Antioxidant enzyme activities were examined in their lung tissue.4. The lung weight did not change in any group. At hatching, the heart weight (g and %) was higher in the O and O groups than in the O and control groups, but the relative heart weight was the highest in the O group in comparison with the O group.5. Superoxide dismutase (SOD) activity increased in all experimental groups at both ages, but glutathione peroxidase (GPx) activity increased only in seven day old chicks. Catalase (CAT) exhibited high activity in the O and O groups at hatching. In the seven day old chicks, while the CAT activity did not change in the O group, it decreased in the O group and increased in the O group.6. Glutathione reductase (GR) activity did not change in the O group, but GR exhibited low activity in the O group and high activity in the O group in newly hatched chicks. The GR activity only decreased in the O group of seven day old chicks.7. The results indicated that oxygen supplementation to the incubator caused alterations in the antioxidant enzyme activities in the lungs of broiler chicks, and this may have been in response to oxidative stress.