Internally pipped eggs were allowed to equilibrate for 1 h at
the normoxic conditions, followed by a measurement of inflow
and outflow oxygen content using a Sable Systems Field Oxygen
Analysis System. Prior to measurement with the O2 analyzer,
the gas was passed through columns of drierite, ascarite,
and drierite. The output from the O2 analyzer was recorded with
an ADInstruments Powerlab 8SP and Chart 5 for later analysis.
Following the initial measurements of O2 at the air cell and the
rest of the egg, the gas content was altered. Eight combinations
of hypoxia and hyperoxia to the air cell and/or egg were tested on
eight sets of eggs and are listed in Table 1. Carbon dioxide to
the air cell was maintained at 5% during all treatments. After
changing the O2 content of the gas, the eggs were allowed to
equilibrate for 1 h at the new O2 levels and the inflow and
outflow O2 was recorded again. Oxygen consumption at the air
cell and the rest of the eggs were calculated using the equation
of Hill (1972) and expressed as mL O2 min−1. Total oxygen
consumption of the egg (V ·
O2total ) was calculated as V ·
O2lung
plusV · O2CAM. All oxygen consumption values were corrected to
standard temperature, pressure and dry (STPD).