Adaptive timing of digestion and digestion-related thermogenesis in the pigeon

• Published in: Physiology & behavior 2003-03, Vol.78 (3), p.441-448
• Main Authors: Laurila, Mirja, Hohtola, Esa, Saarela, Seppo, Rashotte, Michael E
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Animals; Biological and medical sciences; Body temperature; Body Temperature Regulation - physiology; Circadian Rhythm - physiology; Columbidae - metabolism; Defecation - physiology; Digestion; Digestion - physiology; Diurnal rhythm; Faecal excretion; Feces; Feeding; Female; Fundamental and applied biological sciences. Psychology; Male; Restricted feeding; Thermogenesis; Thermogenesis - physiology; Thermoregulation; Thermoregulation. Hibernation. Estivation. Ecophysiology and environmental effects; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/S0031-9384(03)00031-3

Pigeons were allowed to feed for 1 h either 2 h after lights on (morning pulse) or 3 h before lights off (evening pulse). Body temperature was measured radiotelemetrically. Faecal excretion, as an index of rate of digestion, was measured using load cells. At 22 °C, faecal excretion peaked just after lights-on in morning-pulse condition, but not in evening-pulse condition. In the cold (+5 °C), the peak was absent. We conclude that at thermoneutrality, pigeons are able to postpone a major part of digestion until late in the dark phase when their body temperature is increasing to the diurnal level. Thus, the extra heat from digestion-related thermogenesis that otherwise would be dissipated into the environment can be used for rewarming. In the cold, such a delay is not necessarily advantageous as the extra heat can always be used to substitute for thermoregulatory thermogenesis. The occurrence of concentrated period of digestion only in the morning-pulse condition was correlated to a lower food intake and lower body temperature as compared with the evening-pulse condition. Restricted feeding may thus be needed to induce adaptive timing of digestion as a mechanism of energy sparing. In addition to storage of food, timing of digestion may be a significant factor in the evolution of the crop in birds.