How does time since feeding affect the fuels pigeons use during flight?

Area of Science:

• Avian physiology
• Metabolic regulation
• Exercise science

Background:

• Intermeal intervals vary significantly across species.
• Understanding fuel utilization during flight is crucial for avian energetics.
• Previous research has not fully elucidated the impact of feeding status on flight metabolism.

Purpose of the Study:

• To investigate how time since feeding affects lipid, protein, and carbohydrate oxidation in flying pigeons.
• To determine the influence of feeding status on metabolic fuel selection during flight.
• To correlate blood metabolite changes and mass loss with feeding intervals.

Main Methods:

• Five pigeons (Columba livia) were subjected to food deprivation periods of 2, 12, 24, and 48 hours.
• Pigeons were then either flown or rested for 4 hours.
• Blood plasma metabolite concentrations (uric acid, beta-hydroxybutyrate) and body mass changes were measured before and after flight/rest.

Main Results:

• Flight increased plasma uric acid and beta-hydroxybutyrate, indicating elevated protein and lipid catabolism.
• Lipid oxidation (beta-hydroxybutyrate) was higher in unfed flying pigeons compared to fed or resting controls.
• Protein oxidation (uric acid) increased with longer food deprivation, particularly in 48-h deprived pigeons.
• Unfed pigeons lost less mass during flight, with calculated glycogen stores explaining mass loss differences.

Conclusions:

• Time since feeding is a critical determinant of fuel selection in flying pigeons.
• Pigeons adjust their metabolic strategies, shifting towards lipid and protein oxidation when food-deprived.
• These findings have implications for understanding avian flight energetics and survival strategies.