Body temperature, oviposition, and food intake in the hen during continuous light

Egg-laying increases body temperature to an annual maximum in a wild bird

Most birds, unlike reptiles, lay eggs successively to form a full clutch. During egg-laying, birds are highly secretive and prone to disturbance and predation. Using multisensor data loggers, we show that average daily body temperature during egg-laying is significantly increased (1 °C) in wild eider ducks (Somateria mollissima). Strikingly, this increase corresponds to the annual maximum body temperature (40.7 °C), representing a severe annual thermogenic challenge. This egg-laying-induced rise in body temperature may prove to be a common feature of wild birds and could be caused by habitat-related thermoregulatory adjustments and hormonal modulation of reproduction. We conclude our findings with new perspectives of the benefits of high body temperature associated with egg-laying of birds and the potential effect of heat stress that may occur with the future advent of heatwaves.

Circadian rhythmicity of body temperature and metabolism

This article reviews the literature on the circadian rhythms of body temperature and whole-organism metabolism. The two rhythms are first described separately, each description preceded by a review of research methods. Both rhythms are generated endogenously but can be affected by exogenous factors. The relationship between the two rhythms is discussed next. In endothermic animals, modulation of metabolic activity can affect body temperature, but the rhythm of body temperature is not a mere side effect of the rhythm of metabolic thermogenesis associated with general activity. The circadian system modulates metabolic heat production to generate the body temperature rhythm, which challenges homeothermy but does not abolish it. Individual cells do not regulate their own temperature, but the relationship between circadian rhythms and metabolism at the cellular level is also discussed. Metabolism is both an output of and an input to the circadian clock, meaning that circadian rhythmicity and metabolism are intertwined in the cell.

The intake pattern and feed preference of layer hens selected for high or low feed conversion ratio

Feed accounts for the greatest proportion of egg production costs and there is substantial variation in feed to egg conversion ratio (FCR) efficiency between individual hens. Despite this understanding, there is a paucity of information regarding layer hen feeding behaviour, diet selection and its impact on feed efficiency. It was hypothesised that variation in feed to egg conversion efficiency between hens may be influenced by feeding behaviour. For this experiment, two 35-bird groups of ISA Brown layers were selected from 450 individually caged hens at 25–30 weeks of age for either low FCR < 1.8 ± 0.02 (high feed efficiency (HFE) or high FCR > 2.1 ± 0.02 (low feed efficiency (LFE)). For each of these 70 hens, intake of an ad-libitum mash diet at 2-minute time intervals, 24 h a day, for 7 days was determined alongside behavioural assessment and estimation of the selection of components of the mash. The group selected for HFE had a lower feed intake, similar egg mass and associated lower FCR when compared with the LFE group. Whilst feed intake patterns were similar between HFE and LFE hens, there was a distinct intake pattern for all layer hens with intake rate increasing from 0300 to 1700 h with a sharp decline to 2200 h. High feed efficiency hens selected a diet with 25% more ash and 4% less gross energy than LFE hens. The LFE hens also spent more time eating with more walking events, but less time spent resting, drinking, preening and cage pecking events as compared with HFE hens. In summary, there was no contrasting diurnal pattern of feed consumption behaviour between the groups ranked on feed efficiency, however high feed efficiency hens consumed less feed and selected a diet with greater ash content and lower gross energy as compared with LFE hens. Our work is now focused on individual hen diet selection from mash diets with an aim of formulating precision, targeted diets for greater feed efficiency.

Integration of biological clocks and rhythms

Animals, plants, and microorganisms exhibit numerous biological rhythms that are generated by numerous biological clocks. This article summarizes experimental data pertinent to the often-ignored issue of integration of multiple rhythms. Five contexts of integration are discussed: (i) integration of circadian rhythms of multiple processes within an individual organism, (ii) integration of biological rhythms operating in different time scales (such as tidal, daily, and seasonal), (iii) integration of rhythms across multiple species, (iv) integration of rhythms of different members of a species, and (v) integration of rhythmicity and physiological homeostasis. Understanding of these multiple rhythmic interactions is an important first step in the eventual thorough understanding of how organisms arrange their vital functions temporally within and without their bodies.

Procedures for numerical analysis of circadian rhythms

This article reviews various procedures used in the analysis of circadian rhythms at the populational, organismal, cellular and molecular levels. The procedures range from visual inspection of time plots and actograms to several mathematical methods of time series analysis. Computational steps are described in some detail, and additional bibliographic resources and computer programs are listed.

Circadian rhythm of the preovulatory surge of luteinizing hormone and its relationships to rhythms of body temperature and locomotor activity in turkey hens

Simultaneous measurements of plasma LH, body temperature, and locomotor activity were made in laying turkey hens and are reported. Blood samples were remotely collected using a jugular cannula system, and body temperature and locomotor activity were remotely monitored using a radiotelemetry system in freely moving laying turkeys. Under a photoschedule of 14L:10D, the period for preovulatory surges of LH was 25.7 +/- 0.4 h while the periods for peak body temperature and onset of sustained locomotor activity were 24.9 +/- 0.4 and 25.7 +/- 0.5 h, respectively. During exposure to constant light, the periods for preovulatory surges of LH, peak body temperature, and onset of sustained locomotor activity increased to 27.9 +/- 0.9, 26.7 +/- 0.7, and 27.4 +/- 0.7 h, respectively. With the 14L:10D photoschedule, initiation of LH surges was restricted to the scotophase, but after 8 days of constant light, initiation of LH surges had dispersed throughout the 24-h subjective day and night. With constant light, the amplitude of the peak body temperature rhythm decreased, while the duration of the locomotor activity rhythm became broadened and, in some birds, disorganized. Peak body temperature and onset of locomotor activity rhythms and LH surges did not coincide, even though peak body temperature, onset of locomotor activity, and LH surges had similar periods. It is concluded that 1) the photoschedule influences the periods of the LH surge, peak body temperature, and onset of locomotor activity; and 2) a specific or direct relationship between the rhythms of LH surge, body temperature, and locomotor activity remains to be determined in laying turkey hens.

Evidence for separate control of estrous and circadian periodicity in the golden hamster

To study the relationship between estrous and circadian periodicity, we investigated the period of the estrous cycle in two types of female golden hamsters: normals (circadian period approximately 24 h) and tau mutants (circadian period approximately 20 h). Records of running wheel activity, general locomotor activity, body temperature, vaginal secretion, and sexual receptivity of hamsters kept under constant lighting conditions indicated an estrous period of approximately 96 h for both groups of animals. The fact that animals with different circadian periods have the same estrous period suggests the existence of separate mechanisms in the control of circadian and estrous periodicity. Circadian periodicity is determined by a pacemaker located in the suprachiasmatic nuclei, whereas estrous periodicity is determined by positive and negative feedback loops involving the hypothalamus, pituitary, and gonads. Coupling of the two mechanisms takes place under at least some conditions, but additional research is necessary to elucidate the mechanisms by which this is accomplished.

The circadian rhythm of body temperature

This paper reviews the literature on the circadian rhythm of body temperature (CRT). The review starts with a brief discussion of methodological procedures followed by the description of known patterns of oscillation in body temperature, including ultradian and infradian rhythms. Special sections are devoted to issues of species differences, development and aging, and the relationships between the CRT and the circadian rhythm of locomotor activity, between the CRT and the thermoregulatory system, and between the CRT and states of disease. A section on the nervous control of the CRT is followed by summary and conclusions.

Feeding time and body temperature interactions in broiler breeders

Four groups of 70-wk-old broiler breeder females were fed once daily at 0600, 1000, 1400, and 1800 h to determine the effect of feeding time and eating on body temperature. The photoperiod was from 0430 to 1930 h. Four floor pens of 30 hens each were assigned per feeding time. Following a 9-day adjustment period, body temperature was determined, in series, by rectal probe of 5 birds/pen at 7 and 3 h prefeeding and 1, 5, 9, and 13 h postfeeding. Body temperature was increased .5 C at 1 h postfeeding in all groups and at 5 h postfeeding in the 0600-h fed group. The rate of feed consumption was fastest with afternoon feeding. Four 1-yr-old broiler breeder males were implanted with an FM radio transmitter for monitoring body temperature and housed in an environmental control chamber. Body temperature was monitored when the birds were fed at 0600, 1000, 1400, and 1800 h. The chamber temperature cycled from 22.2 to 33.3 C (22.2 C: 2200 to 0800 h; 33.3 C: 1200 to 1600 h; 27.8 C: 0800 to 1200 h and 1600 to 2200 h). Lights were on from 0430 to 1930 h. Body temperature changes were also monitored under constant temperature (27.8 C) and light for birds fed ad libitum or at 1000 h. Body temperature increased as much as 1.5 C following feeding and reached a maximum at 5, 4, 3, and 2 h postfeeding at feeding times of 0600, 1000, 1400, and 1800 h, respectively. Males unable to feed displayed a significantly increased body temperature when they observed other birds eating. A specific body temperature response to feeding activity was observed only when males were fed once daily under constant environment.