Daily cycles in body temperature, metabolic rate, and substrate utilization in pigeons: influence of amount and timing of food consumption

• Published in: Physiology & behavior 1995-04, Vol.57 (4), p.731-746
• Main Authors: Rashotte, Michael E., Basco, Patrick S., Henderson, Ross P.
• Format: Article
• Language: English
• Subjects: Animals; Basal Metabolism - physiology; Biological and medical sciences; Body temperature; Body Temperature - physiology; Body Weight - physiology; Circadian cycles; Circadian Rhythm - physiology; Columbidae - physiology; Conditioning, Operant - physiology; Drinking Behavior - physiology; Eating - physiology; Energy metabolism; Energy Metabolism - physiology; Fasting; Fasting - physiology; Feeding; Feeding Behavior - physiology; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Male; Metabolic rate; Nocturnal hypothermia; Oxygen Consumption - physiology; Pigeons; Respiratory quotient (RQ); Restricted feeding; Time Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/0031-9384(94)00315-7

Pigeons lived in individual chambers where instantaneous metabolic rate (MR; indirect calorimetry), body temperature ( T b), and substrate utilization (RQ) were measured 24 times each hour throughout the 12h:12h light:dark cycle. The amount of food consumed influenced the amplitude of the MR and T b cycles, primarily by affecting the dark-phase segment of the cycle: when food was consumed ad lib, low-amplitude daily cycles in MR and T b occurred in which levels in the dark phase were lower than in the light; during reduced food intake in restricted feeding or in fasting, high-amplitude cycles occurred primarily because nocturnal hypometabolism and hypothermia developed; in restricted feeding, the level of MR and T b during the dark-phase segment of the cycle was directly related to short-term variation in amount consumed. The timing of food consumption primarily affected the light-phase segment of the MR and T b cycles: when feeding was restricted to a time late in the light phase, these measures became depressed early in the light phase, and then greatly elevated near the scheduled time of feeding. This distinctive light-phase pattern developed quickly after the restricted feeding schedule began and may reflect the influence of a circadian food-entrainable oscillator. RQ indicated carbohydrate utilization for most of the 24-h cycle during ad lib feeding and in restricted feeding. However, approximately 2 h before the first feeding bout of the day, the RQ cycle indicated a sizable shift towards lipid utilization, which terminated after the bout was completed. There was a smaller, more transient, decrease in RQ near the time of the light-dark transition, which may imply cessation of digestive activity in preparation for the nocturnal decrease in T b. During fasting, RQ indicated lipid utilization throughout the entire cycle. Whole-day energy expenditure by pigeons in these laboratory circumstances was shown to be closely related to the changes in within-day cycles associated with variations in the amount and timing of food intake.