The purpose of this experiment was to provide information relevant to the current debate concerning the optimisation of terminal stocking density for commercial broiler production. In a modern, controlled-environment house with 24 floor pens (each 11.4 m2), 4020 day-old broilers (Ross 308) were allocated to three terminal (42 days) stocking densities (28, 34 and 40 kg m-2) x two sexes x four replicates, according to a randomised block design. Group sizes varied from 130 to 208. Husbandry conditions were in accordance with normal commercial practice. Performance and behaviour were measured systematically during each of the six weeks of life, and additional measurements were made of leg health and litter condition. Data were analysed using ANOVA to determine the effects of stocking density, sex and age. The realised mean terminal stocking densities were 28.2, 33.5 and 38.5 kg m2. The main significant effects of stocking density treatment were a linear decline in food intake with increasing density during week six (the final week), and a reduced proportion of time spent panting deeply during weeks five and six at the lowest density. Increased (shallow and deep) panting shown by females in weeks two to five suggests that if thermal discomfort becomes a problem at higher stocking densities later in the growing period, it may do so earlier in females. There was no conclusive evidence from this study that broiler welfare is compromised any more at 40 than at 34 kg m−2. The fact that the proportion of time spent panting deeply in week six was considerably lower at 28 kg m2 than at 34 and 40 kg m−2 suggests that thermal comfort (and hence welfare) at this age may be improved at densities of less than 34 kg m−2. However, the significant effects of age, age x density, and age x sex on time spent panting deeply suggest that the age at slaughter and the sex of birds in single-sex flocks should be taken into account in future considerations of optimal maximum terminal stocking density.

The aim of this study was to assess optimal temperature ranges for fattening pigs of different weights kept in pens with partially slatted floors. We examined the behavioural and adrenocortical responses of pigs of different weights (25–35 kg, 50–70 kg, and >85 kg) to a wide range of ambient temperatures (2–29°C). On three days of each experimental period, we took saliva samples for the analysis of cortisol concentration, and recorded lying behaviour from 0800–0600h. Behavioural and cortisol parameters were analysed using linear mixed effects models. Optimal temperature ranges for the three weight-classes were calculated using logistic regression. Pigs chose different areas for resting depending on ambient temperature. With increasing temperature, pigs used the dung area more often and lay more often without contact with pen mates. Compared to lighter pigs, heavier pigs lay without contact with pen mates at lower temperatures. In general, lying without contact occurred at temperatures 5–7°C lower than lying in the dung area. Huddling increased with decreasing temperature, and, with increasing weight, pigs showed huddling at lower temperatures. There was a significant increase in cortisol levels at high ambient temperatures in pigs >85 kg. In pens with partially slatted floors, the results indicate temperature ranges within the thermal tolerance of pigs to be 19–21°C for pigs weighing 25–35 kg (lying area of 0.46 m2/pig), 10–17°C for pigs between 50–70 kg and 5–17°C for pigs >85 kg (both weights: lying area of 0.67 m2/pig).

In the wild, rabbits (Oryctolagus cuniculus) are social but territorial. Recent surveys suggest that over half of pet rabbits are housed singly. We aimed to compare welfare in single versus paired rabbits. We predicted singletons would show more abnormal or escape behaviour, greater stress responses to handling, and reduced body temperature (being unable to huddle with another individual when cold), but that pairs may show aggression. This study was conducted during winter at a rabbit-only rescue centre, and included 45 rabbits, comprising 15 housed singly and 15 pairs. Like most pet rabbits, they were housed either outdoors or in unheated outbuildings. Singletons were mostly in smaller enclosures than pairs. Home-pen observations (40 min) revealed bar-biting in 8/15 single rabbits compared with 0/30 of the paired ones. No other behavioural effects of social housing reached significance, and enclosure size showed no significant effects. Body temperature was significantly lower in singletons than pairs, with at least 0.5°C mean difference. On colder days, rabbits adopted compact postures more, and relaxed postures less frequently. After handling, pairs resumed normal behaviour significantly more quickly than singletons in the home-pen (3.0 [± 0.3] versus 8.3 [± 1.3] s, respectively). Aggression was never observed. The results indicate that social housing reduces bar-biting, aids thermoregulation, and may help buffer stress. Rabbit owners should be encouraged to meet the need for rabbits to be housed with an appropriate conspecific in a suitably large, sheltered enclosure.

Individual gestation housing of pregnant sows in stalls from four weeks after mating is banned in the EU. Two experiments were conducted to study the effect of two gestation management and housing systems (STALL: gilts housed in stalls and PEN: gilts loose-housed in pens with increased feed ratio) on gilt and piglet performance during lactation. Thirty-seven PEN and 33 STALL gilts were used. Backfat, litter pre-weaning mortality and total feed intake (TFI) during lactation were recorded in gilts. Weight and rectal temperature was recorded in piglets. In Exp 1 the behaviour of a subsample of gilts was videotaped during lactation. In Exp 2 saliva cortisol in gilts, thyroid stimulating hormone (TSH) and T4 hormones in piglet blood were measured. PEN gilts had more backfat when moved to the farrowing stalls. PEN gilts tended to have higher cortisol concentration 24 h after entering the farrowing stall and to spend more time sitting or standing up one day before parturition than STALL gilts. PEN piglets had higher bodyweight (BW) on day 0 (Exp 2) and lower T4 concentration than STALL piglets. However, STALL piglets showed higher rectal temperature 60 min after birth and lower mortality at day 2. In Exp 2, STALL piglets also had higher BW and average daily gain at weaning. During lactation, PEN gilts lost more backfat and weaned less piglets. Gilts loose-housed with increased feed ratio during gestation might be more stressed when housed in farrowing stalls than those kept in stalls during gestation, thus compromising their offsprings’ thermoregulatory capacity and growth however, from our results, it is difficult to differentiate the effect of feed level from the effect of allocation during gestation.

In growing pigs, reduced growth during heat stress (HS) is mainly related to decreased feed intake. The study aimed to determine whether the reported positive effects of live yeast (LY) supplementation in HS pigs were due to a modified feeding behaviour or energy metabolism, and if these can be replicated by imposing an increased meal frequency. The effect of LY supplementation (0 (NS) v. 100 (LY) g/ton of feed), and of feeding window (FW) (unlimited or Unli, 2FW of 1 h each and 8FW of 15 min each) were measured in entire male finishing pigs (n 36). Ambient temperature was at 22°C during the thermoneutral (TN) period (5 d) and at 28°C during the HS period (5 d). Heat exposure decreased DM intake (DMI) and retained energy (RE) (–627 and −460 kJ·kg BW–0·60 · d–1, respectively; P < 0·01). During HS, LY supplementation in Unli pigs decreased inter-meal intervals (P = 0·02) attenuating HS effect on DMI which tended to improve RE (P = 0·09). NS – 8FW had higher DMI and RE than NS – 2FW (P < 0·05) but protein deposition (PD) were similar. Supplemented pigs had higher PD during HS regardless of FW (+18 g · d–1; P = 0·03). Comparing the 2FW groups, improved heat tolerance of LY-supplemented pigs were due to improved insulin sensitivity (P < 0·05) and latent heat loss capacity after a meal (P < 0·05) allowing them to increase their DMI (via an increased number of meals) and thus their energy efficiency. Imposing an increased meal frequency improved DMI in HS pigs but did not replicate positive effects of LY on PD.

This study examined the effect of ambient temperature on energy intake, perceived appetite and gut hormone responses during rest in men. Thirteen men (age 21·5 (sd 1·4) years; BMI 24·7 (sd 2·2) kg/m2) completed three, 5·5 h conditions in different ambient temperatures: (i) cold (10°C), (ii) thermoneutral (20°C) and (iii) hot (30°C). A standardised breakfast was consumed after fasting measures, and an ad libitum lunch provided at 4–4·5 h. Blood samples (analysed for plasma acylated ghrelin, total peptide tyrosine-tyrosine (PYY) and total glucagon-like peptide 1 (GLP-1) concentrations), perceived appetite and thermoregulatory responses were collected throughout. Linear mixed models were used for statistical analyses. Ad libitum energy intake was 1243 (sd 1342) kJ higher in 10°C and 1189 (sd 1219) kJ higher in 20 v. 30°C (P = 0·002). Plasma acylated ghrelin, total PYY and GLP-1 concentrations did not differ significantly between the conditions (P ≥ 0·303). Sensitivity analyses for the 4 h pre-lunch period showed that perceived overall appetite was lower in both 30 and 10°C when compared with 20°C (P ≤ 0·019). In conclusion, acutely resting in a hot compared with a thermoneutral and cold ambient temperature reduced lunchtime ad libitum energy intake in healthy men. Suppressed perceived appetite may have contributed to the reduced energy intake in the hot compared with thermoneutral ambient temperature, whereas gut hormones did not appear to play an important role.

Ruminants living in seasonal environments face a two-fold challenge during winter. The energetic cost of maintaining a high body temperature is higher at lower ambient temperatures, and this is compounded by poor availability and quality of feed. Wild ruminants acclimatize to this energetic challenge by hypothermia, that is, reduced endogenous heat production and abandoning the maintenance of a high body temperature, particularly in peripheral body parts. Further but lesser contributions to lower energy expenditure during winter are reduced foraging activity; lower heat increment of feeding; and reduced maintenance cost of size-reduced organs. Altogether, metabolic rate, estimated by the continuous measurement of heart rate, during winter is downregulated to more than half of the summer level, as is voluntary food intake, even in animals fed ad libitum. The transformation from the summer into the thrifty winter phenotype is also evident in the physiology of digestion. Microbial protein synthesis is less facilitated by diminished phosphorus secretion into the shrunk rumen during winter. In line with this result, the concentration of ammonia, the end-product of protein digestion in the rumen, peaks in rumen liquid in spring, whereas the molar proportion of acetate, an indicator of fermentation of a diet rich in fiber, peaks in winter. In contrast to reduced stimulation of growth of ruminal microbes during winter, active transport of nutrients across the intestinal epithelium is increased, resulting in more efficient exploitation of the lower amount and quality of ingested winter feed. Nevertheless, the energy balance remains negative during winter. This is compensated by using fat reserves accumulated during summer, which become a major metabolic fuel during winter.

Both extinct and extant hominin populations display morphological features consistent with Bergmann's and Allen's Rules. However, the functional implications of the morphologies described by these ecological laws are poorly understood. We examined this through the lens of endurance running. Previous research concerning endurance running has focused on locomotor energetic economy. We considered a less-studied dimension of functionality, thermoregulation. The performance of male ultra-marathon runners (n = 88) competing in hot and cold environments was analysed with reference to expected thermoregulatory energy costs and the optimal morphologies predicted by Bergmann's and Allen's Rules. Ecogeographical patterning supporting both principles was observed in thermally challenging environments. Finishers of hot-condition events had significantly longer legs than finishers of cold-condition events. Furthermore, hot-condition finishers had significantly longer legs than those failing to complete hot-condition events. A degree of niche-picking was evident; athletes may have tailored their event entry choices in accordance with their previous race experiences. We propose that the interaction between prolonged physical exertion and hot or cold climates may induce powerful selective pressures driving morphological adaptation. The resulting phenotypes reduce thermoregulatory energetic expenditure, allowing diversion of energy to other functional outcomes such as faster running.

Poor performance and ill-health of calves in the pre-wean period can affect future productivity. Increasing numbers of producers are opting to use calf jackets as a means of mitigating the potential negative effects of low ambient temperatures, wind speed and precipitation on growth and health. This study aimed to use a range of noninvasive monitoring technologies to investigate the effects of using calf jackets in the first 3 weeks of life on calf performance and behavioural and physiological parameters. Ninety Holstein-Friesian calves were allocated to one of the two treatments: (i) Jacketed until 21 days of age and (J; n = 44) ii. Nonjacketed (NJ; n = 46). Calves were group housed and fed milk replacer (MR) and concentrate solid feed via automatic feeders. Calves were weaned at day 56, and the experiment was completed at day 63. Health assessments were conducted on a daily basis throughout the experiment using predefined faecal and respiratory scoring protocols. A range of novel, noninvasive monitoring technologies were used to examine the activity, heart rate and thermal profiles of calves on an individual basis throughout the experimental period. There were no differences in calf live weight (LWT), average daily gain (ADG) or feed conversion efficiency (FCE) in J and NJ calves between days 5 to 20. However, NJ calves consumed more MR and had more unrewarded visits to the milk feeder than J calves during this period. Although calf LWT was comparable across treatments in the week following jacket removal (days 21 to 28), both ADG and FCE tended to be greater in NJ calves. There were no treatment differences in calf LWT at the end of the study (d63). When measured over a period of 24 h and at a mean ambient temperature of 7.7°C, skin surface temperature was 6.37°C higher in J calves. Core body temperature was higher in J calves between days 5 to 20; however, there were no differences in IR eye or IR rectal temperature. No differences in lying behaviour occurred, with calves spending 18 and 17 h/day lying between days 5 to 20 and days 21 to 28, respectively. Under the climatic and management conditions described, no significant benefits to calf performance were found as a result of the provision of calf jackets to group-housed calves in the first 3 weeks of life. The higher frequency of unrewarded visits to the milk feeder in NJ calves during the first 3 weeks of life could be suggestive of a lack of satiety in these calves.

The objective of this study was to estimate the genetic parameters for thermoregulation traits and the relationships with performance of Large White lactating sows reared in a tropical humid climate. The thermoregulation traits were rectal temperature (RT), cutaneous temperature (CT) and respiratory rate (RR) during lactation measured in the afternoon (1200 h) and in the morning (0700 h). The production traits were sow’s average daily feed intake (ADFI), litter BW gain (LBWg) and sow’s proportion of BW change between farrowing and weaning (BWc). Complete data included 931 lactating performance on 329 Large White sows from the INRA experimental unit in Guadeloupe (French West Indies). Random regression models using linear spline functions were used for longitudinal data (RT, CT, RR and daily feed intake). Results showed that when ignoring values at the beginning and the end of lactation, the traits studied can be treated as the same trait throughout days of lactation, with fairly constant heritability and variance. However, largest heritabilities and genetic variances were estimated in mid-lactation. Heritability estimates on average performance during lactation were low to moderate for thermoregulation traits (0.35±0.09 for RT, 0.34±0.12 for CT and 0.39±0.13 for RR). Heritability estimates for production traits were 0.26±0.08 for ADFI, 0.20±0.07 for BWc and 0.31±0.09 for LBWg. Significant genetic correlations between thermoregulation traits and production traits were only obtained for ADFI and RR (0.35±0.12). From this study it can be concluded that thermoregulation traits are heritable, indicating that there are genetic differences in heat stress tolerance in lactating Large White sows.

Selection programs have enabled broiler chickens to gain muscle mass without similar enlargement of the cardiovascular and respiratory systems that are essential for thermoregulatory efficiency. Meat-type chickens cope with high ambient temperature by reducing feed intake and growth during chronic and moderate heat exposure. In case of acute heat exposure, a dramatic increase in morbidity and mortality can occur. In order to alleviate heat stress in the long term, research has recently focused on early thermal manipulation. Aimed at stimulation of long-term thermotolerance, the thermal manipulation of embryos is a method based on fine tuning of incubation conditions, taking into account the level and duration of increases in temperature and relative humidity during a critical period of embryogenesis. The consequences of thermal manipulation on the performance and meat quality of broiler chickens have been explored to ensure the potential application of this strategy. The physiological basis of the method is the induction of epigenetic and metabolic mechanisms that control body temperature in the long term. Early thermal manipulation can enhance poultry resistance to environmental changes without much effect on growth performance. This review presents the main strategies of early heat exposure and the physiological concepts on which these methods were based. The cellular mechanisms potentially underlying the adaptive response are discussed as well as the potential interest of thermal manipulation of embryos for poultry production.

Since the rediscovery of brown adipose tissue (BAT) in adult human subjects in 2007, there has been a dramatic resurgence in research interest in its role in heat production and energy balance. This has coincided with a reassessment of the origins of BAT and the suggestion that brown preadipocytes could share a common lineage with skeletal myoblasts. In precocial newborns, such as sheep, the onset of non-shivering thermogenesis through activation of the BAT-specific uncoupling protein 1 (UCP1) is essential for effective adaptation to the cold exposure of the extra-uterine environment. This is mediated by a combination of endocrine adaptations which accompany normal parturition at birth and further endocrine stimulation from the mother's milk. Three distinct adipose depots have been identified in all species studied to date. These contain either primarily white, primarily brown or a mix of brown and white adipocytes. The latter tissue type is present, at least, in the fetus and, thereafter, appears to take on the characteristics of white adipose tissue during postnatal development. It is becoming apparent that a range of organ-specific mechanisms can promote UCP1 expression. They include the liver, heart and skeletal muscle, and involve unique endocrine systems that are stimulated by cold exposure and/or exercise. These multiple pathways that promote BAT function vary with age and between species that may determine the potential to be manipulated in early life. Such interventions could modify, or reverse, the normal ontogenic pathway by which BAT disappears after birth, thereby facilitating BAT thermogenesis through the life cycle.

Arid Mediterranean regions that shelter unique biodiversity are threatened by increasing anthropogenic pressures, such as urbanization, overgrazing and climate change. In Morocco, one of the main bush species in arid areas, the jujube (Ziziphus lotus), suffers from officially promoted programmes of removal. The Moorish tortoise (Testudo graeca soussensis) is threatened by such habitat loss. Like most animals, the Moorish tortoise must navigate between microhabitats to find essential feeding resources and thermal refuges. This study combined radio-tracking of free-ranging individuals, microhabitat temperature monitoring and transects in a range of habitats. Tortoises were found to depend on the occurrence of large and relatively abundant bushes to escape lethal overheating. Thus, (1) current official encouragements for the destruction of the jujube bushes should be reappraised; (2) habitat restoration relying on replanting jujube bush should be encouraged; and (3) large-scale monitoring of critical bush densities should be used to better organize conservation plans (protection and/or restoration of areas) for the Moorish tortoise.

The “radiator” theory of brain evolution is proposed to account for “mosaic evolution” whereby brain size began to increase rapidly in the genus Homo well over a million years after bipedalism had been selected for in early hominids. Because hydrostatic pressures differ across columns of fluid depending on orientation (posture), vascular systems of early bipeds became reoriented so that cranial blood flowed preferentially to the vertebral plexus instead of the internal jugular vein in response to gravity. The Hadar early hominids and robust australopithecines partly achieved this reorientation with a dramatically enlarged occipital/marginal sinus system. On the other hand, hominids in the gracile australopithecine through Homo lineage delivered blood to the vertebral plexus via a widespread network of veins that became more elaborate through time. Mastoid and parietal emissary veins are representatives of this network, and increases in their frequencies during hominid evolution are indicative of its development. Brain size increased with increased frequencies of mastoid and parietal emissary veins in the lineage leading to and including Homo, but remained conservative in the robust australopithecine lineage that lacked the network of veins. The brain is an extremely heatsensitive organ and emissary veins in humans have been shown to cool the brain under conditions of hyperthermia. Thus, the network of veins in the lineage leading to Homo acted as a radiator that released a thermal constraint on brain size. The radiator theory is in keeping with the belief that basal gracile and basal robust australopithecines occupied distinct niches, with the former living in savanna mosaic habitats that were subject to hot temperatures and intense solar radiation during the day.