Respiratory exchanges in the incubated egg of the domestic guinea fowl

Abstract

The daily O 2 uptake (Ṁ O 2 ) and CO 2 production (Ṁ CO 2 ) rates were measured in guinea fowl eggs with a wide range of mass specific shell water vapor conductance, spG H 2O [0.108 to 0.365 mg·(g·Torr·day) −1], from day 10 to the end of incubation, day 28. The respiration rate showed a plateau, from day 22 to day 24, typical of a precocial bird: M ̇ O 2 ≈ 21.4 and M ̇ CO 2 ≈ 15.2 mmol·day −1 . The plateau Ṁ O 2 value was that predicted by allometric relation. At the plateau, respiratory exchanges appeared significantly limited by spG H 2O . The limiting effect of spG H 2O on respiratory metabolism began as soon as day 18 (64% of incubation time). The respiratory ratio was 0.75 at day 10, decreased to 0.65–0.66 on days 12–14 and stabilized at 0.70–0.71 on days 20–28.