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CO2 and avian eggshell formation at high altitude.
S C Hempleman1, F L Powell, T P Adamson
1Department of Medicine, University of California, San Diego, La Jolla 92093.
Respiration Physiology
|January 1, 1992
Summary
High altitude reduces eggshell conductance and thickness in hens due to hypocapnia. Relieving hypocapnia paradoxically worsened these effects, suggesting other factors influence eggshell quality at altitude.
Area of Science:
- Animal Physiology
- Avian Biology
- Environmental Physiology
Background:
- Altitude exposure can induce hypocapnia (low CO2 levels) in birds.
- Hypocapnia is hypothesized to affect eggshell formation and gas exchange properties.
Purpose of the Study:
- To test if altitude-induced hypocapnia reduces eggshell conductance to water vapor (GH2O) in hens.
- To investigate the impact of hypocapnia on eggshell thickness and pore area.
Main Methods:
- Seven laying hens were exposed to different altitudes (1200 m, 3800 m) and conditions (3800 m with added CO2).
- Egg GH2O was measured gravimetrically.
- Shell thickness was measured, and aggregate pore area was calculated using Fick's law.
Main Results:
- At 3800 m, GH2O, shell thickness, and pore area were reduced compared to 1200 m.
- Relieving hypocapnia at 3800 m + CO2 further reduced GH2O and pore area, while increasing shell thickness.
- The initial hypothesis was rejected based on these findings.
Conclusions:
- Hypocapnia is responsible for thin eggshells at high altitudes.
- Other physiological factors, not hypocapnia, likely cause reduced eggshell GH2O and pore area at altitude.