Measurement of flight energy demands using labelled bicarbonate
There have been two projects run under this program, both involved PhD studentships. In the first, Susan Thomson on a BBSRC studentship developed a method for measuring energy costs of short duration behaviours using turnover of an injected bolus of C-13 labelled bicarbonate, as part of a wider project on quantifying heat balance during flight in bats. The bicarbonate elimination method was validated against indirect calorimetry in mice and then later in small insectivorous bats (Pipistrellus pygmaeus). The validation equation in bats was then used to evaluate flight energy demands of bats when they were engaged in short duration flights. The estimated flight energy expenditures of this bat were not significantly different from estimates of flight cost made previously in the same species using the doubly-labelled water technique.
Publications
SPEAKMAN, J.R. and Thomson, S.C. (1997)
Validation of the labeled bicarbonate technique for measurement
of short term energy expenditure in the mouse.
Zeitschrift Fur Ernahrungswissenschaft 36: 273-277
Developing on from the preliminary work in bats a second studentship has addressed the energy demands of short duration flights in birds. This project was a CASE studentship funded by BBSRC and The Waltham Centre for Pet Nutrition. The PhD student working on the project was Catherine Hambly.
The 13C labelled bicarbonate technique was developed for use with small birds, namely zebra finches, orange-tufted sunbirds, cockatiels and starlings. The validation of the technique involved comparing the isotope elimination rate with known metabolism measured using indirect calorimetry. Isotope elimination rate is the gradient of the isotope enrichment with time.
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Cockatiels used to evaluate the energy cost of flight when carrying artificial loads |
Once this relationship had been established flight costs were measured by calculating the elimination rate over the flight period. Metabolic rate was then predicted for the flight period using the validation. This led to a series of experiments to examine the affect that increased wing loading, wing asymmetry and short bursts of flight had on the energetic cost of flight. This included a period of work in Israel in collaboration with Professor Berry Pinshow under the Lord Goodman fellowship scheme, applying the method to evaluate the energy demands of flight in Orange tufted sunbirds.
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Orange tufted Sunbird female |
Publications
Hambly C, Harper EJ and Speakman (Submitted) Cost of flight in the zebra finch (Taenopygia guttata): a novel approach based on elimination of 13C labelled bicarbonate.
Hambly C, Harper EJ, Speakman JR (2000) Cost of flight in the zebra finch (Taenopygia guttata): a novel approach based on elimination of C-13 labelled bicarbonate in breath. FASEB J 14 (4): A595-A595