Figure 1. ¹³C enrichment in expired CO₂ in eggs incubated at two different eggshell temperatures (study I).

¹³C enrichment in expired CO₂ after injecting a single bolus of [U-¹³C]glucose (1.0 mg in 250 µL sterile water) in the chorio-allantoic fluid at day 14.5 of incubation of embryos incubated at a normal (37.8°C) or high (38.9°C) eggshell temperature (EST) from day 13 of incubation onward.