Gas Exchange of the Ostrich Embryo During Peak Metabolism in Relation to Incubator Design.

Oxygen (O2) consumption and carbon dioxide (CO2) excretion of ostrich embryos were studied on 45 ostrich eggs in various stages of development. A closed respirometry system was used for eggs subjected to ≤ 10 days of incubation, while an open flow system was used for older eggs. A total of 102 measurements were made and repeat measurements on the same egg were treated as independent during statistical analysis. The O2 consumption and CO2 excretion of ostrich embryos increased exponentially during the first 70% of incubation, reaching a maximum between day 31 and 38 of incubation. During peak metabolism about 180 ml/h of O2 was consumed and 120 ml/h carbon dioxide (CO2) was excreted. This stage was followed by a decline in metabolic rate to approximately 75 % of the peak value. The gas exchange of ostrich eggs incubated in this study at 36 °C was compared with studies where incubation temperatures of 35, 35.5 and 36.3 °C were used. Although the time of hatch differed between these studies (41, 44.6 and 47 days) in contrast to the 42 day incubation period in the present study, the general trends in O2 consumption and CO2 excretion were broadly similar, although there were slight differences in the plateau phases. From the data on O2 consumption and CO2 excretion during peak embryo metabolism (ca. 32 to 37 days of incubation), it was calculated that an airflow of 54.2 l/egg hour-1 is needed to prevent a decline in O2 levels to below 21% and an increase in CO2 concentration to levels exceeding 0.3% in single stage incubators. This airflow is less than that required for chicken eggs incubated in the same single stage incubator. Results of this study will enable incubator operators incubating ostrich eggs to adjust ventilation rates to accommodate embryonic age and metabolism and to avoid costly heat loss because of excessive ventilation.