Altitude hypocapnia at 2,800 m does not affect development of the chicken embryo

Eggs laid at sea level and incubated at high altitude are subject to hypoxia, hypocapnia, and excessive water loss, resulting in retarded development and poor hatchability. The effect of altitude hypocapnia alone was studied in two series of eggs incubated at a simulated altitude of 2,800 m, PB = 542 torr; the incubator was ventilated at a low flow rate with O2-enriched air; the relative humidity was 70-74%, PH2O 34.4-36.4 torr; ambient PO2 about 130 torr at the plateau stage. In the normocapnic series, CO2 produced by the embryos increased ambient PCO2 to 14 torr at 18-19 days; altitude hypoxia, hypocapnia, and excessive water loss were practically compensated for. In the hypocapnic series, ambient CO2 was almost completely absorbed by soda lime, so that only hypocapnia was not compensated for. In 17-19-day eggs with similar sea level mass specific shell conductances [sp GH2O = 0.26-0.25 mg [g.d.torr]-1], the measured PO2 in the gas space, hematocrit, hemoglobin concentration, lengths of beak and third toe, and masses of body and brain were essentially the same in both series. The masses of heart, liver, and left wing were slightly different on day 19. Altitude hypocapnia alone, without altitude hypoxia and excessive water loss, had almost no significant effect on the embryos' development and hatchability.