Higher Mean Body Temperature Research Articles

Perioperative risk factors for long-term intelligence in children with postoperative cerebellar mutism syndrome after medulloblastoma surgery.

Approximately 7%-50% of children with medulloblastoma (MB) develop postoperative cerebellar mutism syndrome (pCMS). pCMS has a short-term negative impact on intelligence, but effects on long-term outcomes are contradictory. The aim of this study was to assess long-term effects of pCMS in MB patients on aspects of intelligence quotient (IQ) and its perioperative risk factors. In this single-center retrospective cohort study, 31 children were included (14 pCMS). Perioperative risk factors included brainstem invasion, vermis incision, hydrocephalus, tumor size, severity of pCMS, neurological symptoms, mean body temperature (BT) on days 1-4 post surgery, and age at resection. Age-appropriate Wechsler Intelligence tests were assessed at least 2years after tumor resection. Mean interval between tumor resection and neuropsychological evaluation was 3.9years in pCMS and 4years and 11months in the no-pCMS group. No significant differences in IQ scores were found between groups. The pCMS group had a clinically relevant difference of 10 points when compared to age norms on verbal IQ (VIQ). Bilateral pyramidal and swallowing problems were risk factors for lower performance. In the overall group, tumor size, younger age at surgery, and raised mean BT were negatively correlated with aspects of IQ. We found a clinically significant reduction of VIQ in the pCMS patient group. pCMS patients with a larger tumor size, younger age at surgery, a higher mean BT in the first days after surgery, bilateral pyramidal symptoms, and swallowing problems 10days post surgery are more at risk for VIQ deficits at long-term.

Effect of massage therapy on preterm neonate's body temperature.

Low-cost care strategies can be implemented to avert the morbidity and mortality associated with hypothermia in preterm neonates. To determine the effect of massage therapy on body temperature of preterm neonates. A quasi-experimental design was conducted among 72 preterm neonates at a level II special care nursery in Western Kenya. Neonates were recruited on the third day of life and followed up for 10 days. Neonates in the intervention group were massaged three times a day for 15 minutes. Body temperature was monitored and recorded before, during and after each therapy session. Neonates in the control group received routine care: temperature monitoring three times a day, feeding and diaper change. Neonates who received massage had higher mean body temperature than the control group during therapy on day 6 (p = .019) and after therapy on day 6 (p = .017) and day 8 (p = .005). A comparison within massage group (before/during, during/after, before/after) showed an increase in mean body temperature during therapy compared to before therapy (p <.001) and after therapy compared to before therapy (p <.001). Massage therapy increases body temperature in preterm neonates.

How influential are squamate reptile traits in explaining population responses to environmental disturbances?

Abstract Context Understanding how organismal attributes influence sensitivity to environmental perturbations is a central theme in ecology and conservation. Certain traits, such as body size, habitat use, dietary preference and reproductive output are considered important determinants of animal species’ responses to the impacts of ecological disturbances. However, the general relationships between functional traits and post-disturbance responses by animals are not fully understood. AimsOur primary aim was to use a meta-analysis to evaluate the influence of species traits on variation in population abundances of squamate reptiles (i.e. lizards and snakes). MethodsWe extracted data from 107 original published studies, from which 1027 mean effect sizes of post-disturbance responses by 298 species were estimated. We examined short-term responses only (i.e. within 3 years since the most recent disturbance). A comprehensive range of disturbances was examined, such as habitat destruction, fragmentation, fire, and exotic-species invasions. We used Bayesian linear mixed-effect modelling (BLMM), utilising the Markov-chain Monte Carlo algorithm (MCMC) for the meta-regression. Specifically, we tested the influence of eight species traits (body size, diet, temporal activity pattern, sociality, reproductive mode, clutch size, habitat selection, and mean body temperature), along with disturbance type, in explaining variation in species-specific abundance responses of squamate reptiles post-disturbance. Key resultsPost-disturbance abundance responses of squamate species were significantly influenced by two parameters, namely, mean body temperature and clutch size. In general, significant positive responses post-disturbance were observed for species with higher mean body temperatures and a greater clutch size. The type of disturbance had no detectable influence on squamate abundances. The influence of random effects (heterogeneity among studies and species, and broad taxonomic identity) accounted for more of the model variation than did the fixed effects (species traits and disturbance type). ConclusionsCertain species traits exerted some influence on the sensitivities of lizards and snakes to ecological disturbances, although the influence of random effects was very strong. Our findings are likely to be a result of the complexity and idiosyncratic nature of natural abundance patterns among animal species, in addition to the potential confounding effect of methodological differences among studies. ImplicationsThe present study is the first major quantitative synthesis of how species traits influence population-level responses of squamate reptiles to ecological disturbances. The findings can be used to guide conservation efforts and ecological management, such as by prioritising the efforts of mitigation on species that reproduce more slowly, and those with lower body temperatures.

Immune-mediated neurological manifestations of dengue virus- a study of clinico-investigational variability, predictors of neuraxial involvement, and outcome with the role of immunomodulation

Our aim was to study dengue-related immune-mediated neurological complications (IMNC) during the recent epidemic. This was a cross-sectional observational study of 79 IMNC cases from 1627 laboratory confirmed dengue cases from January 2015 to January 2016 and their follow-up for 3 months. According to the World Health Organization, cases were categorized into those having dengue fever (DF), and those having a severe syndrome that includes dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Laboratory as well as clinicoradiological data, the predictors of outcome, and the role of immunomodulation in determining the final result were analyzed. Out of the 1627 confirmed dengue cases, 14.6% developed neurological complications and only 4.86% cases had IMNC. Among the IMNC seen, the majority of the patients had the onset of their manifestations in the subacute (7-30 days) latency period; however, there was no mortality seen. We found Miller Fisher syndrome (MFS), limbic encephalitis, and immune-mediated cerebellar demyelination (IMCD) as the new findings in the IMNC spectrum. Patients with DF were more prone to developing brachial plexus neuritis and polyneuritis cranialis, whereas those patients with a severe syndrome were more commonly associated with Guillain-Barre syndrome (GBS). Significant (P < 0.001) predictors of central nervous system involvement were anemia, an elevated hematocrit, and the presence of DSS, whereas patients with a higher mean body temperature, DF, and elevated hematocrit were more prone to developing peripheral nervous system manifestations. The platelets counts and the hemoglobin levels had a negative correlation whereas the hematocrit value, the mean body temperature, and the alanine aminotransferase levels had a moderately significant positive correlation for the development of IMNC. The immunomodulatory therapy (IMT), if initiated after fever abatement led to a significant clinically favorable outcome at 3 months, especially in patients with GBS, polyneuritis cranialis, and brachial plexus neuritis. The spectrum of IMNC is vast and may include MFS, limbic encephalitis and IMCD. Early initiation of IMT, in the presence of significant predictors, may reduce the IMNC-related morbidity.

Thermal biology of the spotted snow skink, Niveoscincus ocellatus, along an altitudinal gradient

Body temperatures in ectotherms are strongly affected by their thermal environment. Ectotherms respond to variation in the thermal environment either by modification of behavioural thermoregulation to maintain their optimal body temperature or by shifting their optimal body temperature. In this study, the body temperatures of males of three populations of spotted snow skinks, Niveoscincus ocellatus, living along an altitudinal gradient (low, mid, and high altitude) were studied in the field and laboratory in spring, summer, and autumn, representing the full activity period of this species. The environmental variation across both sites and seasons affected their field active body temperatures. At the low and mid altitude, N. ocellatus had a higher mean body temperature than at the high altitude. Animals achieved their thermal preference at the low and mid altitude sites in all seasons. At the high altitude, however, N. ocellatus struggled to reach its preferred body temperatures, especially in autumn. The lower body temperature at the high-altitude site is likely due to limited thermal opportunity and/or an effect of avoiding the costs associated with increased intensity of basking.

Risk factors for development of postoperative cerebellar mutism syndrome in children after medulloblastoma surgery.

OBJECTIVE Postoperative cerebellar mutism syndrome (pCMS) occurs in 7%-50% of children after cerebellar tumor surgery. Typical features include a latent onset of 1-2 days after surgery, transient mutism, emotional lability, and a wide variety of motor and neurobehavioral abnormalities. Sequelae of this syndrome usually persist long term. The principal causal factor is bilateral surgical damage (regardless of tumor location) to any component of the proximal efferent cerebellar pathway, which leads to temporary dysfunction of cerebral cortical regions as a result of diaschisis. Tumor type, cerebellar midline location, and brainstem involvement are risk factors for pCMS that have been identified repeatedly, but they do not explain its latent onset. Ambiguous or negative results for other factors, such as hydrocephalus, postoperative meningitis, length of vermian incision, and tumor size, have been reached. The aim of this study was to identify perioperative clinical, radiological, and laboratory factors that also increase risk for the development of pCMS. The focus was on factors that might explain the delayed onset of pCMS and thus might provide a time window for taking precautionary measures to prevent pCMS or reduce its severity. The study was focused specifically on children who had undergone surgery for medulloblastoma. METHODS In this single-center retrospective cohort study, the authors included 71 children with medulloblastoma, 28 of whom developed pCMS after primary resection. Clinical and laboratory data were collected prospectively and analyzed systematically. Variables were included for univariate and multivariate analysis. RESULTS Univariate regression analysis revealed 7 variables that had a significant influence on pCMS onset, namely, tumor size, maximum tumor diameter > 5 cm, tumor infiltration or compression of the brainstem, significantly larger decreases in hemoglobin (p = 0.010) and hematocrit (p = 0.003) in the pCMS group after surgery than in the no-pCMS group, significantly more reported incidents of severe bleeding in the tumor bed during surgery in the pCMS group, preoperative hydrocephalus, and a mean body temperature rise of 0.5°C in the first 4 days after surgery in the pCMS group. Multiple regression analysis revealed that tumor size, tumor infiltration into or compression of the brainstem, and higher mean body temperature in the first 4 postoperative days were independent and highly significant predictors for pCMS. CONCLUSIONS The authors confirmed earlier findings that tumor-associated preoperative conditions, such as a maximum tumor diameter ≥ 5 cm and infiltration into or compression of the brainstem, are associated with a higher risk for the development of pCMS. Most importantly, the authors found that a 0.5°C higher mean body temperature in the first 4 postoperative days increased the odds ratio for the development of pCMS almost 5-fold. These data suggest that an important focus for the prevention of pCMS in children who have undergone medulloblastoma surgery might be rigorous maintenance of normothermia as standard care after surgery.

Competition during thermoregulation altered the body temperatures and hormone levels of lizards

Summary Every organism must thermoregulate to maximize its performance, but competing organisms limit access to preferred microclimates. Such competition often creates hierarchies in which dominant individuals have more access to limited resources than subordinate individuals. To assess the costs of competition during thermoregulation, we measured thermoregulation, movement, and hormones of male lizards (Sceloporus jarrovi) when alone and when paired with a smaller or larger conspecific. Large males were 31% closer to the heat source when paired than when alone, resulting in a higher mean body temperature (35·7 vs. 33·9 °C). Conversely, small males were 40% farther from the heat source when paired, resulting in lower mean body temperature (32·1 vs. 33·6 °C). When paired, large and small males circulate 26 and 44% more corticosterone, respectively. Conversely, large males circulated 26% more testosterone when paired, whereas small males circulated 26% less testosterone. Both dominant and subordinate males incurred costs when paired, including poorer thermoregulation, more movement and greater physiological stress. Thus, competition for thermal resources should feature more prominently in ecological and evolutionary models of thermoregulation. A lay summary is available for this article.

Neurologic complications in dengue virus infection: a prospective cohort study.

This study aimed to evaluate the incidence and clinical spectrum of neurologic complications, predictors of central and peripheral nervous system involvement, and their outcome in patients with dengue virus infection (DENV). To determine the extent of neurologic complications, we used a hospital-based prospective cohort study design, which included laboratory-confirmed cases of dengue and follow-up for 3 months. We also analyzed clinical and laboratory data to assess predictors of neurologic involvement. The study included enrollment of 486 cases. Two were lost to follow-up and excluded. Forty-five patients developed neurologic complications. Of these, 28 patients had CNS and 17 had peripheral nervous system (PNS) involvement, representing an incidence rate for neurologic complications of 9.26%. Significant predictors of CNS involvement were higher mean body temperature (p = 0.012), elevated hematocrit (p = 0.009), low platelet count (p = 0.021), and liver dysfunction (p < 0.001). Predictors of PNS involvement were higher mean body temperature (p = 0.031), rash (p = 0.002), and elevated hematocrit (p < 0.001). The mortality rate was 4.5%. The remainder of the patients recovered. An increasingly wide spectrum and higher incidence of neurologic complications of DENV are reported. Clinical and laboratory parameters such as higher mean body temperature, rash, increases in hematocrit, thrombocytopenia, and liver dysfunction are independent predictors of neurologic complications.

The effect of electrically heated humidifier on the body temperature and blood loss in spinal surgery under general anesthesia.

BackgroundGeneral anesthesia often produces some degree of hypothermia and hypothermia causes much more blood loss during surgery than normothermia. Electrically heated humidifiers (EHHs) have been used for patients under general anesthesia and in the intensive care unit. However, the benefits of the EHH have not been widely reported in the literature.MethodsPatients scheduled for posterior lumbar spine fusion, were randomly assigned to a mechanically ventilated with EHH circuit group or to a conventional respiratory circuit group. Their tympanic membrane temperature was monitored every 30 min after induction up to 180 min, and perioperative blood losses, transfusion requirements during surgery, and other complications were noted.ResultsPatients in the control group (n = 40) showed a lower mean body temperature at all times than immediately after induction, while the EHH group (n = 40) showed a lower body temperature from 60 minute after induction comparing to the initial temperature. Furthermore, patients in the EHH group had a higher mean body temperature than patients in the control group during surgery (35.9 ± 0.4 vs 35.4 ± 0.5, P < 0.001). Mean intraoperative blood loss (9.75 ± 5.4 vs 7.48 ± 3.9, P = 0.035) and transfusion requirements (57.5% vs 25%, P = 0.006) were significantly less in the EHH group, but postoperative blood loss, duration of hospitalization, and other complications were not significantly different in the two study groups.ConclusionsThe use of an electrically heated humidifier did not prevent a body temperature drop under general anesthesia. However, it helped maintain body temperature and was associated less blood loss and transfusion requirement during surgery.

Clinical features, aetiology and short-term outcome of interstitial pneumonitis in HIV/AIDS patients at Bamrasnaradura Hospital, Nonthaburi, Thailand

This prospective study was conducted at Bamrasnaradura Hospital from November 11, 2002, until January 5, 2003, in order to describe the clinical manifestations and determine the aetiologies as well as to assess the short-term outcome of interstitial pneumonitis in HIV/AIDS patients. 59 patients with interstitial infiltrates on chest radiographs were included in the study. Tuberculosis (TB) was the most common diagnosis (44%), followed by Pneumocystis pneumonia (PCP) (25.4%), bacterial pneumonia (20.3%) and fungal pneumonia (10.2%). In TB, compared to other diagnoses, a mild cough (p = 0.031), pallor (p = 0.021), lymphadenopathy (p < 0.001), an absence of skin lesions (p = 0.003), a higher mean body temperature (p = 0.004) and an absence of dyspnoea on exertion (p = 0.042) were significant findings. In PCP, compared to other diagnoses, dyspnoea on exertion (p = 0.014), nonpurulent sputum production (p = 0.047), a higher mean respiratory rate (p < 0.001), and an absence of lymphadenopathy (p < 0.001) were significant factors. In bacterial pneumonia, compared to other diagnoses, production of purulent sputum (p = 0.014), haemoptysis (p = 0.006), skin lesions (p = 0.002) and severe cough (p = 0.040) were significantly associated factors. In fungal pneumonia, compared to other diagnoses, headache and papulonecrotic skin lesions were common findings, but no factor showed a significant association. After four weeks, 59.3% patients were alive and 13.6% had died. Among those alive, 88.6% had clinically improved. The cumulative survival after 28 days was highest among PCP patients, followed by bacterial pneumonia, TB and fungal pneumonia, but these differences were statistically not significant (p = 0.453).

Thermal Adaptations of the Leaf BeetleChrysomela lapponica(Coleoptera: Chrysomelidae) to Different Climes of Central and Northern Europe

This study investigated the physiologically adaptive significance of elytral coloring and other thermal adaptations to different climes of Central and Northern Europe in a leaf beetle. Adults of Chrysomela lapponica L. differ in the coloring pattern of their red and black elytra when comparing populations from Finnish Lapland (Northern Europe) and from the Czech Republic (Central Europe). While the elytra of adults of the Czech population were bright red in color with a proportion of 51% of black marks, the relative size of the black marks of the Finnish beetle’s elytra was significantly higher (68%). When exposed to light, the dark morphs from Finland increased their body temperature within a shorter time and reached higher mean body temperatures than the lighter morphs from the Czech Republic. The walking speeds of the two different morphs did not differ at temperatures of 20, 15, and 10°C. However, at 5°C, the walking speed of the melanic beetles from Finland was significantly higher. The specific metabolic rate during overwintering of the adults was significantly higher in the Finnish morph at a temperature of 5°C compared with the Czech morph. The average and maximum temperatures during overwintering in the leaf litter layer in the Czech Republic were more variable and on average higher than under the snow cover in Finland. These results on the thermoregulation in C. lapponica are discussed with special respect to melanic elytral coloring as adaptation toward lower ambient temperatures.

An experimental test of the link between foraging, habitat selection and thermoregulation in black rat snakes Elaphe obsoleta obsoleta

Summary Most physiological processes are temperature‐dependent. Thus, for ectotherms, behavioural control of body temperatures directly affects their physiology. Ectotherms thermoregulate by adjusting habitat use and therefore thermoregulation is probably the single most important proximate factor influencing habitat use of terrestrial reptiles, at least in temperate climates. Snakes have been shown to raise their body temperature following feeding in a laboratory thermal gradient, presumably to enhance digestion. This experiment was exported to the field to explore the link between feeding, habitat selection and thermoregulation in free‐ranging snakes. Experimental feeding was conducted in the laboratory and in the field on black rat snakes (Elaphe obsoleta obsoleta) that had temperature‐sensitive radio‐transmitters surgically implanted. Snakes had higher mean body temperatures following feeding than prior to feeding in a laboratory thermal gradient. Some, but not all evidence, indicated that black rat snakes increased their mean body temperature following feeding in the field. Indices of thermoregulation indicated that the snakes thermoregulated more carefully and more effectively after they had eaten. Forest edges provided the best opportunities for thermoregulation in the study area. Black rat snakes were less likely to move following feeding when fed in edges than when fed in the forest and were more likely to be found in edges following feeding, whether they had been fed in the forest or in an edge. Results of this study and one previous study suggest that thermoregulatory behaviour of snakes following feeding in the laboratory is a reliable predictor of their behaviour in the field. A review of 13 studies of the thermoregulatory behaviour of snakes following feeding in the laboratory revealed that not all species behave similarly. However, the quality and number of studies currently available is not adequate for testing hypotheses about which species should change thermoregulatory behaviour in response to eating and which should not.

ENDOTOXIN ELICITS A FEBRILE RESPONSE IN LABORATORY-MAINTAINED BUT NOT FREE-LIVING CALIFORNIAGROUND SQUIRRELS

Abstract California ground squirrels (Spermophilus beecheyi) in the natural environment maintain a higher mean body temperature (Tb) compared with animals maintained in the laboratory. Our goal was to determine whether that increase was the result of an elevation in Tb set point analogous to a fever induced by acute stress. Body temperatures were measured by telemetry in a paired experiment on 10 animals maintained in the laboratory, with each animal receiving an injection of sterile pyrogen-free saline and 50 μg/kg endotoxin of E. coli. Body temperatures also were measured by telemetry on 8 pairs of free-living animals, with 1 member receiving an injection of sterile saline and the other animal receiving an injection of 50 μg/kg endotoxin of E. coli. Animals maintained in the laboratory exhibited a fever following injection of endotoxin, with significant elevation in Tb from 6 to 9 h after injection. Free-living animals that were injected with endotoxin did not exhibit an increase in Tb compared with sal...

Comparison of thermoregulatory characteristics of patients with intra- and suprasellar pituitary adenomas.

Thermoregulatory capabilities under physiologic cold and heat exposure of 37 patients with suprasellar pituitary adenomas (As) and 10 patients with intrasellar adenomas (Ai) were analyzed and compared to each other and to 13 controls (Ctr.) In Ai no shift of the thermoregulatory threshold temperatures was observed. In As the regulation was shifted to a 0.5 degrees C higher mean body temperature in 82% of the patients, indicating a "set-point" elevation. The accuracy of the regulation against thermal loads was maintained, the velocity was reduced. Postoperative examination of As revealed a normalisation of the "set-point". Modifications of the hypothalamic amine systems by the compressive effect of the suprasellar adenomas are discussed to be the most probable cause for the observed thermoregulatory alterations.

Thermal Consequences of Reptilian Viviparity: Thermoregulation in Gravid and Nongravid Garter Snakes (Thamnophis)

Reptilian viviparity is assumed to have evolved in response to cool climates, because of the developmental benefits of maternal thermoregulation. However, very few data are available to test this assumption and there is currently little evidence of a consistent pattern of thermoregulation associated with viviparity. I used temperature-sensitive radiotelemetry to measure the differences in thermoregu- lation between gravid and nongravid garter snakes (Thamnophis sirtalis and T. elegans). Gravid females had higher mean body temperatures and thermoregulated more precisely than did nongravid females. These differences in thermoregulation persisted throughout gestation, but disappeared relatively quickly following parturition. Gravid females thermoregulated with high precision despite voluntarily selecting a wide range of mean Tbs indicating that precision may be a critical, although largely overlooked, com- ponent of the thermal relations of viviparous reptiles. The differences in thermoregulation between gravid and nongravid Thamnophis suggest that viviparity imposes an energetic cost, but determining the mag- nitude of the cost will require more information on the relationship between temperature and metabolic rate.

Acetazolamide alters temperature regulation during submaximal exercise

Acetazolamide (ACZ), a potent carbonic anhydrase inhibitor, is known to decrease submaximal exercise tolerance under normoxic and hypoxic conditions. These decrements in performance occur despite the maintenance of O2 consumption and CO2 removal. Because ACZ is a diuretic, it induces a moderate hypohydration that may have a role in reducing the ability to sustain exercise through cardiovascular and thermoregulatory impairment. To investigate this potential impairment, seven healthy males between 21 and 35 yr of age were studied in a double-blind crossover design (placebo vs. ACZ). ACZ was administered in three 250-mg oral doses 14, 8, and 2 h before exercise. Subjects exercised at 70% peak O2 uptake for 30 min on a cycle ergometer in a normoxic thermoneutral environment (25 degrees C, 40% relative humidity). Results indicate that exercise minute ventilation was greater but O2 uptake, CO2 output, and respiratory exchange ratio did not differ with ACZ. ACZ led to lower mean skin (0.7 degrees C), higher rectal (0.6 degrees C), and higher mean body temperatures (0.4 degrees C) after 30 min of exercise. Whole-body sweat loss was reduced 23%, and heat storage during the exercise bout was increased 55%. Stroke volume decreased 25%, and arteriovenous O2 difference increased 15%. A significant inverse relationship (r = -0.63) between heart rate and stroke volume was observed. It is concluded that previously reported decreases in the ability to sustain submaximal exercise with ACZ may be related to hypohydration-induced impairment of the cardiovascular and thermoregulatory systems.

Thermal ecology and diet of some xerophilous lizards from western New South Wales

Daily and seasonal assessments were made of the thermal ecology of four coexisting lizard species from the New South Wales arid zone, varying in size between 5 and 700 g. The smaller species (Tympanocryptis lineata, Amphibolurus nuchalis) were observed only during hotter periods and had higher mean body temperatures (>37°C), while the larger species (A. vitticeps, Trachydosaurus rugosus) preferred thermally more moderate periods and had lower mean body temperatures (

A comparison of preruminant bull calves of the Hereford × Friesian, Aberdeen Angus × Friesian and Friesian breeds

ABSTRACTTwenty-four bull calves, eight Hereford × Friesian, eight Aberdeen Angus × Friesian and eight Friesian, were reared from birth to slaughter at 13 weeks of age solely on a milk substitute diet given ad libitum.Samples of jugular blood were taken at weekly intervals from 5 days to 89 days of age for determination of concentrations of prolactin, growth hormone (GH), insulin and total thyroxine (T4) in plasma, tri-iodothyronine (T3) uptake, and thus free T4 index (FTI).The Friesian calves had a higher mean body temperature and lower mean T3 uptake than did either of the beef crosses.The Aberdeen Angus cross had a higher mean dry-matter intake per unit of metabolic body size (DMI/W0·73), heart rate and plasma insulin concentration than did the Hereford cross, and a higher insulin concentration but not a higher heart rate than did the Friesian. Live-weight gain and DMI/W0·73 for the Friesian was intermediate between that of the Aberdeen Augus cross and the Hereford cross.DMI/W0·73 was positively correlated with insulin: GH ratio, prolactin: GH ratio and T4: GH ratio.The increase in heart rate per unit DMI/W073, a measure of the heat increment of feeding, was negatively correlated with the plasma insulin concentration, insulin: T4 and insulin: GH ratios.Prolactin concentration, GH concentration and T3 uptake declined with age, whereas insulin concentration, T4 concentration and FTI increased with age. The relationship was linear for prolactin and insulin concentrations, but curvilinear for the other variables. The Friesian breed had a higher GH concentration than did the beef crosses during the first 12 days of life. The large increase in insulin concentration for the Aberdeen Angus × Friesian occurred from about 47 days of age. The peak T4 concentration and the lowest T3 uptake of the breeds occurred between 33 and 42 days of age.Possible mechanisms for the control of dry-matter intake by preruminant calves and the difficulties associated with prediction of performance from plasma metabolic hormone concentrations obtained at a young age are discussed.