Lower Heat Production Research Articles

Nutritional aspects of hydrogenated and regular soybean oil added to diets of broiler chickens

The objective of the present study was to evaluate the effect of degree of saturation of fat incorporated into broiler diets on performance and body fatty acid (FA) profile. The various degrees of saturation were achieved by using regular soybean oil (SO) and hydrogenated soybean oil (HSO), mixed at different proportions. The work was carried out on commercial broilers (Experiment 1) and on lines of chickens divergently selected for high (HF) or low (LF) abdominal fat (Experiment 2). Daily BW gain and gain:feed ratio increased and the amount of feed intake decreased as the dietary fat saturation decreased. Digestibility of total fat and of each of the FA was lowest in the HSO group and reached maximal values when 23% or more of the added oil was SO. The AMEn values of the diets were almost parallel to fat digestibility. The performance of the HF and LF chickens was affected by the degree of saturation similarly to that observed for the commercial stock. The degree of dietary fat saturation had very little effect on saturated FA (C16:0 and C18:0) in body lipids, reduced the level of monoenoic FA (C16:1 and C18:1), and raised that of polyunsaturated FA (PUFA) (C18:2, C18:3, and C20:4). Monoenoic FA were higher, whereas PUFA were lower in the HF than in the LF line. The improved AMEn in diets containing unsaturated fat is probably due to higher fat digestibility, direct deposition of PUFA in body lipids, and lower lipogenesis, associated with lower heat production.

Anomalously low heat flow density in eastern Karelia, Baltic Shield: a possible palaeoclimatic signature

We report new heat flow density (HFD) values in seven drill holes in the Kamennye Lakes area in eastern Karelia, Russia, approximately at latitude 63°15′N, longitude 36°10′E. The investigated holes are 250–750 m deep and they intersect Archaean ultrabasic serpentinites and talc-carbonate rocks. Measured gradients range from 0.8 to 3.7 mK m −1 and the apparent HFD values from 2.4 to 11.6 mW m −2. The holes are not technically disturbed by fluid flow or any drilling effects. Average heat production of the rocks as analysed in the core samples of the deepest measured hole is 0.25 μ W m −3, but the low heat production is not a critical factor in producing the low HFD values. This is due to refraction of heat as shown with 2-D conductive simulations of heat transfer in a low heat-production formation surrounded by higher heat production. Hydrogeological disturbances can be ruled out by the presence of saline groundwater in the sections deeper than 150–400 m, and low topographic variation in the area, as well as Peclet number estimates, which suggest negligible convective heat transfer in the bedrock. All the temperature profiles are curved indicating recent palaeoclimatic disturbances. Inversion studies with singular value decomposition techniques yielded a climatic warming of about 1.0–1.5 K which started 150–200 years ago and was preceded by a cool period which lasted about 100 years. Nevertheless, recent climatic changes cannot explain the very low apparent HFD values, but long-period effects of the Weichselian glaciation are sufficient to decrease the HFD values to the levels measured. These effects were investigated with forward simulations and suggest that present temperature gradients in the range of 1–4 mK m −1 in the uppermost 1 km can be created by a very cold ground temperature (−10 to −15°C) during the glaciation time (60-11 ka ago).

Thermal structure, thickness and composition of continental lithosphere

Global compilations of surface heat flow data from stable, Precambrian terrains show a statistically significant secular change from 41±11 mW/m 2 in Archean to 55±17 mW/m 2 in Proterozoic regions far removed from Archean cratons. Using the tectonothermal age of the continents coupled with average heat flow for different age provinces yields a mean continental surface heat flow between 47 and 49 mW/m 2 (depending on the average, non-orogenic heat flow assumed for Phanerozoic regions). Compositional models for bulk continental crust that produce this much or more heat flow (i.e., K 2O>2.3–2.4 wt%) are not consistent with these observations. More rigorous constraints on crust composition cannot be had from heat flow data until the relative contributions to surface heat flow from crust and mantle are better determined and the non-orogenic component of heat flow in the areally extensive Phanerozoic regions (35% of the continents) is determined. We calculate conductive geotherms for 41 mW/m 2 surface heat flow to place limits on the heat production of Archean mantle roots and to evaluate the significance of the pressure–temperature ( P– T) array for cratonic mantle xenoliths. Widely variable geotherms exist for this surface heat flow, depending on the values of crustal and lithospheric mantle heat production that are adopted. Using the average K content of cratonic peridotite xenoliths (0.15 wt% K 2O, assuming Th/U=3.9 and K/U=10,000 to give a heat production of 0.093 μW/m 3) and a range of reasonable crustal heat production values (i.e., ≥0.5 μW/m 3), we calculate geotherms that are so strongly curved they never intersect the mantle adiabat. Thus the average cratonic peridotite is not representative of the heat production of Archean mantle roots. Using our preferred estimate of heat production in the cratonic mantle (0.03 wt% K 2O, or 0.019 μW/m 3) we find that the only geotherms that pass through the xenolith P–T data array are those corresponding to crust having very low heat production (<0.9 wt% K 2O). If the lithospheric mantle heat production is higher than our preferred values, the continental crust must have correspondingly lower heat production (i.e., bulk crustal K, Th and U contents lower than that of average Archean granulite facies terrains), which we consider unlikely. If the xenolith P–T data reflect equilibration to a conductive geotherm, then Archean lithosphere is relatively thin (150–200 km, based on intersection of the P–T array with the mantle adiabat) and the primary reason for the lower surface heat flow in Archean regions is decreased crustal heat production, rather than the insulating effects of thick lithospheric roots. On the other hand, if the xenolith P–T points result from frozen-in mineral equilibria or reflect perturbed geotherms associated with magmatism, then the Archean crust can have higher heat producing element concentrations, lithospheric thickness can range to greater depths and the low surface heat flow in Archean cratons may be due to the insulating effects of thick lithospheric roots. An uppermost limit for Archean crustal heat production of 0.77 μW/m 3 is determined from the heat flow systematics.

Low geothermal heat flow of the Urals fold belt — implication of low heat production, fluid circulation or palaeoclimate?

The Urals are characterized by extremely low heat flow density (HFD). We present a discussion on the relevant factors which may contribute to the observed distribution of heat flow values. The available heat flow data in the Urals and surrounding East European and West Siberian platforms are based on borehole measurements at about 300 sites which range from the Arctic Sea coast to the Kazakshtan Plain. Along the Urals fold belt heat flow density is 30 mW m −2 or less, whereas the platform areas are characterized by 20–40 mW m −2 higher values. The low heat flow density zone is 50–100 km wide. Its extension to the north is not exactly known, but the minimum extends at least to the latitude 61°N. We present new results of heat flow and heat production measurements, Peclet number analyses on advective heat transfer by groundwater flow, as well as numerical conductive models of heat transfer in the lithosphere in the Troitsk DSS transect. The most important factor contributing to the low heat flow density in the Urals seems to be the low level of radiogenic heat production in the crust in the Tagil-Magnitogorsk Zone. The minimum is apparently enhanced by the palaeoclimatically induced vertical variation in HFD produced by the periglacial climatic conditions during the latest glaciation epoch 70,000–10,000 years B.P. The boreholes used for HFD measurements are shallower (500–1500 m) in the Tagil-Magnitogorsk Zone than in the adjoining areas in the west (1000–3000 m) or in the east (300–3000 m), and therefore the palaeoclimatic disturbance is more pronounced in these boreholes.

On the heat flow variation from Archean cratons to Proterozoic mobile belts

Heat flow data from a number of continental shield regions show a trend of relatively low to high values from Archean cratons to bordering Proterozoic mobile belts. Of the two end‐member explanations for this trend, low heat production in Archean crust or a relatively thick cratonic lithosphere, the latter has come to be generally preferred. Such an explanation assumes a strong, one‐to‐one correspondence between the mantle component of surface heat flow and local lithospheric thickness. This assumption has been well validated below oceans and its applicability to continental lithosphere has gone largely unchallenged. It is, however, not fully valid. This is demonstrated through numerical models that allow continents to form over a convecting mantle. Model continents consist of a core region of thickened crust and mantle residuum and a peripheral region of thick crust, analogs to a craton and a mobile belt, respectively. Despite a thicker thermal lithosphere in the core relative to the periphery, the equilibrium surface heat flux across a continent shows little variation. The finite thermal conductivity of buoyant continental material is at the heart of this behavior as it allows continents to enforce a spatially near‐constant heat flux condition on the mantle below. Such a condition is associated with a weak correspondence between mantle heat flow and lithospheric thickness defined thermally or mechanically. This general result, together with specific modeling results applied to heat flow data, suggests that variable lithospheric thickness is most likely not the primary cause of heat flow variations near Archean cratons, leaving differing degrees of crustal heat production as the more likely candidate.

Heat Production by Brown Adipocytes of FOK Rats Genetically Resistant to a Hot Environment.

The FOK rat was established as an inbred strain with genotypic adaptation to a hot environment. To investigate the mechanism of the heat resistance of FOK rats, heat production by isolated brown adipocytes in FOK and WKAH rats was measured at 37.0 and 39.9 degrees C. Basal heat production by brown adipocytes of FOK rats was not significantly different from that of WKAH rats. Isoproterenol increased the heat production in a dose-dependent manner in both strains, while 10(-9) M isoproterenol caused a significant increase in WKAH rats and a negligible change in FOK rats. These results indicate that the reason why FOK rats are resistant to the severe heat is partly due to the low heat production by brown adipocytes.

On the heat flux related to stretching in the NW-Mediterranean continental margins

The surface thermal flux of the continental margins of the northwestern Mediterranean Sea is interpreted on the basis of a 1-D instantaneous pure shear stretching model of the lithosphere in terms of three components: the background heat flowing out from the asthenosphere (38 mW m−2), the transient contribution depending on the rift age and extension amount (35 mW m−2 at the most), and the contribution due to the radiogenic elements of the lithosphere. The radiogenic component is estimated at the continental margins of the Ligurian-Provencal basin and Valencia trough, and in the surrounding mainland areas by means of available data of surface heat generation from Variscan Corsica, Maures-Esterel and the Central Massif along with a geophysical-petrological relationship between heat production and seismic velocity. The lithosphere radiogenic heat contribution ql decreases with the thinning factor β according to the exponential law: ql(β) = a exp(-bβ), in which factor b is greater for that part of the lithosphere below the uppermost 10 km. Considering also the heat generated by radioactive isotopes in sediments, the stable Variscan lithosphere produces an average thermal flux of 30 mW m−2 which decreases by about one half where the lithosphere is thinned by one third. Although the surface heat generation is 2·1 − 3·3 µW m−3 in the Maures-Esterel massif — excepting small outcrops of dioritic rocks with lower heat production — and 1·8 µW m−3 for most of Corsica, the radiogenic heating within the lithosphere for such areas is nearly the same and does not explain the higher heat flux of the Corsica margin. This asymmetric thermal pattern with surface heat flux which is 10 − 15 mW m−2 higher than predictions is probably of upper mantle origin, or can be ascribed to penetrative magmatism.

Relationships among heat production, body weight, and age in Suffolk and Texel ewes

The objective of this study was to test the null hypothesis that heat production (HP) was equivalent between Suffolk and Texel ewes at common fasted BW and at common ages. Open-circuit respiration calorimetry was used to estimate HP in 48 Suffolk and 48 Texel ewes at eight ages (10, 15, 20, and 28 wk of age and 1.5, 2.5, 3.5, and 4.5 yr of age). Sheep were individually penned in an environmentally controlled building 6 to 10 d before sample collection. Feed was removed 55 h before sample collection. Heat production measurements were made from 55 and 71 h of the feed restriction. Suffolk ewes had greater mature weights (P < .01) and reached maturity more rapidly than Texel ewes (P < .05). At a common weight, Texel ewes had a lower HP than Suffolk ewes. The ratio of HP:BW declined as ewes aged, as indicated by the fact that the slope of the log-transformed data was negative and less than 1 (P < .01). The models predict that Suffolk ewes had a lower HP:BW than Texel ewes at a common age, but when ewes were compared at common proportions of mature weight HP:BW did not differ between breeds. Breed differences in HP seem to be the result of differences between breeds in maturing rate.

Cellular thermogenesis in L-929 mouse fibroblasts. The influence of oxygen availability on growth, heat production and intermediary metabolism

Abstract Cellular thermogenesis in L-929 mouse fibroblasts growing in glass ampoules was monitored over 72 h in three different systems: (1) closed ampoules with 2.5 ml of control medium; (2) closed ampoules with 2.85 ml of medium and a reduced oxygen content; and (3) ampoules kept open. Thermogenesis was determined as heat production (HP) and the pH, and oxygen, glucose and lactate contents in the medium as well as the cellular growth were assessed in order to evaluate whether small gaseous volumes are sufficient to facilitate adequate oxygen supply. Oxygen deficiency resulted in lower HP, decreased growth and enhanced anaerobic rate of glycolysis. Low gas volume was associated with decreased HP after 40 h and a steady increasing rate of aerobic glycolysis similar to that shown during O 2 deficiency. In the open system a more pronounced decrease of HP was observed.

Effect of cycling temperature on growth, energy metabolism and nutrient retention of individual male turkeys.

1. Each week, from 12 to 20 weeks of age, male turkeys of a heavy strain were subjected to cool (C; 16 degrees C), hot (H; 29 degrees C), and cycling temperatures, and fed on a standard diet ad libitum for 4 d. Lighting was intermittent, 3 h on, 3 h off. Food was given when lights were on. Those given cycling temperatures (3 h C; 3 h H) were given food and light during the cool (eat-when-cool, EC) or hot (EH) periods. 2. Birds in all treatments gained similar amounts of weight from 12-14 weeks of age. Thereafter, birds in C maintained gains, the body weight gains of birds in EC and EH declined moderately and birds in H lost weight. 3. Birds in C produced more metabolic heat. Those in H showed increased heat production as they became older. 4. Protein retention was greater in turkeys in C, EC and EH. It was lower in H, becoming negative between 18-20 weeks of age. Birds in H suffered body fat losses which increased with age. 5. Birds in EH and EC gained similar amounts of body weight. Birds in EH exhibited lower heat production and greater energy retention than those in EC. 6. Body temperatures were higher in H than in the other environments.

Thermal regime of the southern Basin and Range Province&amp;colon; 1. Heat flow data from Arizona and the Mojave Desert of California and Nevada

With about 150 new heat flow values, more than 200 values of heat flow are now available from the crystalline terranes of southern California, the Basin and Range Province of Arizona, and Paleozoic sedimentary rocks of the southwestern Colorado Plateau &amp;lpar;CP&amp;rpar;. Heat flow ranges from about 5 mW m&amp;minus;2 on the CP near Flagstaff, Arizona, to more than 150 mW m&amp;minus;2 in the crystalline rocks bordering the Salton Trough in SE California. The heat flow pattern within this region is complex, although it correlates with regional physiographic and tectonic features. Unlike the adjacent Sierra Nevada Batholith where heat flow is a linear function of near&amp;hyphen;surface radiogenic heat production, no statistically significant correlation exists between heat flow and heat production in the study area, possibly because of its complex tectonic history, involving lateral movement of basement terranes, and relatively young heat sources and sinks of different strengths, ages, and durations. Contemporary and Neogene extensional tectonism appears to be responsible for the very high heat flow &amp;lpar;&amp;gt;100 mW m&amp;minus;2&amp;rpar; associated with the Salton Trough and its neighboring ranges, the Death Valley fault zone and its southward extension along the eastern boundary of the Mojave block, and zones of shallow depth &amp;lpar;&amp;lt;10 km&amp;rpar; to the Curie isotherm &amp;lpar;as inferred from aerornagnetic data&amp;rpar; in west central Arizona. Low &amp;lpar;&amp;lt;60 mW m&amp;minus;2&amp;rpar; heat flow in the Peninsular Ranges and eastern Transverse Ranges of California may be caused by downward advection associated with subduction and compressional tectonics. Relatively low heat flow &amp;lpar;67&amp;plusmn;4 mW m&amp;minus;2&amp;rpar; is also associated with the main trend of metamorphic core complexes in Arizona, and the outcropping rocks in the core complexes have a low radioactive heat production &amp;lpar;1.3&amp;plusmn;0.3 &amp;mu;W m&amp;minus;3&amp;rpar; compared to the other crystalline rocks in the region &amp;lpar;2.1&amp;plusmn;0.2 &amp;mu;W m&amp;minus;3&amp;rpar;.

Thermal regime of the southern Basin and Range Province: 2. Implications of heat flow for regional extension and metamorphic core complexes

The average heat flow for the presently quiescent southern Basin and Range Province (82±3 mW m−2) is only marginally lower than that for the northern Basin and Range (92±9 mW m−2), even though the former has been relatively inactive over the past 10–15 m.y. This result is consistent with a broad range of simple homogeneous models for province‐wide extension; the high heat flow (roughly equivalent to doubling the stable mantle contribution) can develop quickly from nonconductive processes (extension, magmatism, delamination), but the decay is a conductive process that might have little effect in the first 10–15 m.y. of quiescence. The frequently cited province‐wide estimate of 100% extension (β = 2) in the Basin and Range is consistent with the observed heat flow but not required by it. Extension models involving lithosphere thinning by delamination (and not solely by stretching), and/or magmatic additions, can provide the observed heat flow with less extension. These models are easier to reconcile with the buoyancy requirements of the present high elevation. Loss of buoyancy required by 100% extension poses special problems; either the preextensional terrain was as high as any on Earth today, or a large compensating source of buoyancy developed during the extension process. Possible candidates are magmatic contributions to the crust (which must be very large to be important in this context), trapped melt or lighter phases in the mantle, or a locally hot plume‐fed upper asthenosphere. Superimposed on the regional scale extension are zones where intense local extension has removed much of the upper crust to form metamorphic core complexes. Two thermal observations might bear on their origin: (1) Relatively low heat flow (67±4 mW m−2) is associated with the main trend of metamorphic core complexes (MCCs) in Arizona, and (2) the outcropping rocks in the core complexes have a low radioactive heat production (1.3±.3 μW m−3) compared to the other crystalline rocks in the region (2.1±.2 μW m−3). These observations are consistent with the belief that radioactivity decreases downward in the crust and that MCCs are sites of massive unroofing. In fact, the measured heat flow low could be explained by the removal of 10–20 km of upper crustal radioactivity provided the opposing effects of transient heating from unroofing were short‐lived. According to an idealized model, this would be the case if the compensating mass flow occurred in the lower crust, not in the mantle. In this sense the regional thermal results provide some support for the lower crustal return flow hypothesis for metamorphic core complexes.

Calorimetric investigations on social thermogenesis in the hornet Vespa crabro L. (Hymenoptera: Vespinae)

Heat production rates of individual hornets were measured at 10, 15, and 20°C by means of direct calorimetry in order to investigate endothermic behaviour and capabilities to contribute to nest heat. Hornet workers showed heat production rates of 49 mW per g wet weight (w.w.) (SD = ±8 mW g −1) at 20°C; drones have lower heat production rates at the same temperature (36 mW g −1, SD = ±5 mW g −1). Nevertheless, the latter may contribute significant portions of heat to the nest at the end of season. The heat production of the whole colony was assessed at 1.8 W at the state of maximum biomass and at 1.3 W later, after the appearance of the reproductive forms, i.e. the drones and queens. The fact that drones and workers lowered their heat production rates with decreasing ambient temperatures in our experiments is discussed.

Fat-cell heat production, adipose tissue fatty acids, lipoprotein lipase activity and plasma lipoproteins in adiposis dolorosa.

1. Gluteal adipose tissue was examined in 13 patients with generalized adiposis dolorosa, a clinical condition characterized by painful adiposity with a chronic intractable course. The total metabolic activity of fat cells, isolated by collagenase and suspended in Krebs-Ringer bicarbonate buffer with glucose and insulin, was assessed by the measurement of heat production at 37 degrees C using microcalorimetry. 2. Fat cells were markedly enlarged; their metabolic activity expressed in terms of microW/g, but not in pW/cell, was significantly decreased when compared with both lean and weight-matched non-painful subjects. Both mean values were, however, significantly higher than in grossly obese subjects with similar mean cell size. Heat production as expressed per g of tissue, but not per cell, was inversely correlated with body mass index. One additional patient had unilateral disease, and fat cells from the painful side had a lower heat production than cells from the unaffected side. 3. The fatty acid composition of adipose tissue, as determined by g.c., revealed a significantly increased proportion of monounsaturated (18:1 and 16:1) at the expense of saturated (14:0 and 18:0) fatty acids compared with healthy control subjects. The activity of adipose tissue lipoprotein lipase was slightly, but not significantly, decreased. 4. It is concluded that a metabolic pathogenetic factor cannot be ruled out in adiposis dolorosa. As the results do not explain the nature of the diffuse pain, further studies need to be performed.

Thermogenesis of white adipocytes: a novel method allowing long-term microcalomrimetric investigations

A microcalorimetric method was developed ti facilitate long-term assessment of energy balance in isolated fat cells. White rat adipocytes were primary cultured in glass ampoules with a matrix of agar-gel. Heat production was measured continuously over 3 days with an LKB BioActivityMonitor. In order to assist interpretation of the microcalometric measurements, glucose consumption and lactate and pyruvate production were determined in parallel cultures. Heat production, glucose consumption and lactate production were in an apparent steady throughout the study whether amploying aerobic (94 pW, 0.50 and 0.44 pmol/cell·h, respectively) or partial anaerobic experimental conditions (39 pW, 0.41 and 0.57 pmol/cell·h, respectively). However, oxygen availability influenced the apparent heat production and glucosen and lactate metabolism. With partial anaerobiosis a 59% lower heat production, an 18% lower glucose consumprion and a 30% higher lactate production than by employing aerobic experimental conditions were observed.

Heat flow and heat generation in the Archaean Dharwar cratons and implications for the Southern Indian Shield geotherm and lithospheric thickness

We report terrestrial heat flow density measurements from 11 new sites in the Archaean Eastern and Western Dharwar cratons of the Southern Indian Shield. The new values, together with already published data, have yielded a mean heat flow of 40 ± 3.4 (s.d.) mW m −2 ( n = 11) for the Eastern Dharwar craton, which is a predominantly gneiss-granite terrain. The mean heat flow in the Archaean supracrustal belts of Western Dharwar craton, which is a granite-greenstone terrain, is 31 ± 4.1 (s.d.) mW m −2 ( n = 4). The observed difference in surface heat flow between the two cratons is ascribed to differences in radiogenic heat production in upper crustal layers, inferred to be related to different crust-forming processes. It has been argued that low heat production appears to be an inherent characteristic of the crust similar to that of the Western Dharwar craton, which evolved during the early Archaean and suffered depletion of the lithophile elements of its lower crust prior to the late Archaean. Radiogenic heat production measurements were carried out on borehole core samples for one heat flow site (Sortur), and data have been compiled from the literature on three other sites and on a variety of rocks of the Southern Indian Shield. Heat flow and radiogenic heat production for Sortur, when combined with the published data, define a linear relation ( r = 0.97) with a slope of 11.5 km and an intercept of 23 mw m −2. The thickness of the thermal lithosphere beneath the Dharwar cratons is over 200 km, thereby indicating, beneath the cratons, the existence of deep continental roots-a concept which is also supported by teleseismic P-wave travel time data. The geothermal data has clearly demonstrated that the Archaean Dharwar cratons of the Indian landmass are associated with low mean surface heat flow (37.7 mW m −2), reduced heat flow, Moho heat flux (12–17 mW m −2), and a cool and thick lithosphere—all characteristics of many Archaean-early Proterozoic terrains of other shields. It is inferred that the thermal structure of the South Indian lithosphere is identical with that of other cratons.

Thermoregulation and Energetic Decision-Making by the Honeybees Apis Cerana, Apis Dorsata and Apis Laboriosa

Summary Thoracic flight temperatures (Tth) of workers of three species of honeybees (genus Apis) in Nepal were measured at relatively low ambient temperatures (Ta). At Ta = 18–24 °C, A. dorsata workers arriving at feeders to collect concentrated (⩾=40%) sugar syrup maintained higher temperature gradients (Tth — Ta) than workers arriving at feeders with dilute (6–17%) syrup. Temperature gradients were inversely related to Ta, indicating thermoregulation at low Ta. Similarly, temperature gradients varied inversely with Ta in A. cerana and A. laboriosa workers arriving at feeders at Ta = 12–20 °C. Temperature data suggest that honeybees have the ability to regulate heat production in flight and that they may vary their flight efforts according to expected gains and associated costs. Temperature gradients of A. laboriosa workers in flight are apparently about the same as those of A. mellifera workers, whose body mass is only half that of A. laboriosa. The circulatory systems of A. laboriosa workers show no striking differences from those of other species of Apis and are therefore probably equally effective at retaining heat in the thorax. This suggests that the relatively low (in relation to the body size) Tth— Ta maintained by A. laboriosa may be an indication of a relatively low metabolic rate and consequent low heat production. This is supported by an analysis of mass1,/3-specific wing-loading and, in turn, suggests that A. laboriosa may be grouped with A. dorsata and A. florea as a relatively low-powered, open-nesting honeybee, in contrast to the more high-powered cavity-nesters, A. cerana and A. mellifera.

Comparative aspects of resistance to body cooling in newborn lambs and kids

ABSTRACTThe aim of this study was to compare responses to cold stress in newborn lambs and kids. Two experiments were conducted in a climatic chamber with controlled air temperatures and artificial wind and rain. The first experiment involved 25 Poll Dorset × (Border Leicester × Romney) lambs and 16 Angora × feral kids while the second involved 30 Suffolk × (Border Leicester × Romney) lambs and 26 Angora × feral kids. Rectal temperatures were measured and the rate of decline in rectal temperature estimated in both experiments. In the second experiment, metabolic rate was also measured and coat characteristics (birth coat depth and wool weight per unit area of skin) were examined. The effects of birth rank and sex on resistance to cold exposure and their interaction with species were examined in both experiments.In experiment 1, kids had lower rectal temperatures than lambs at the start of the test but there was no species effect on the rate of decline in rectal temperature. In experiment 2, kids exhibited a significantly greater rate of decline in rectal temperature than did lambs. This difference in species effect between the experiments reflected primarily a greater rate of body cooling in the Poll Dorset-cross lambs (experiment 1) than in the Suffolk-cross lambs (experiment 2) rather than a difference between the kids in the two experiments. Additionally, in experiment 2, metabolic rate per unit live weight was significantly lower in the kids than in the lambs. No differences were apparent between the species in coat characters. Multiple-born lambs and kids were found to exhibit a significantly greater rate of decline in rectal temperature than singles, but only marginal differences in heat production were observed between the birth ranks. No significant effects of sex on resistance to cold stress were found in this study. Effects of birth rank and sex were additive with those of species. It is concluded that a combination of low heat production capacity and small body size is responsible for the generally poor responses of newborn kids to cold stress but there is probably little difference between lambs and kids in the insulative value of their birth coats.

Difference in energy metabolism and protein retention of limit-fed growing pigs of several breeds.

Energy metabolism and protein retention of four pig breeds were studied in three experiments comparing Norwegian (N) landrace with either Finnish (F) landrace (Exp. 1), Great Yorkshire (Y, Exp. 2) or Dutch landrace (D, Exp. 3). An increasing or decreasing temperature regimen (11 to 26 degrees C) was used. The animals were kept at a constant feeding level (about 93 g.kg -.75.d -1). Energy and protein balances were measured at increasing and decreasing temperature conditions separately. The three landrace breeds utilized their dietary energy and protein with similar efficiencies. However, large differences were observed between Y and N pigs in Exp.2. The Y pigs had a higher growth rate, lower feed/gain, lower heat production, and higher protein deposition than the N pigs. These differences were related to a lower level of activity of the Y pigs. This lower activity level resulted in lower maintenance requirements of the Y pigs compared with the N pigs. Growth rate and feed conversion differed between balance periods. When the temperature within a period was being increased, growth rate was higher and feed/gain was lower compared with periods in which the temperature was being decreased. Breeds differ with respect to energy and protein utilization.

Some remarks on the stability of blueschists and related high P-low T assemblages in continental orogens

The thermal evolution of the crust in continental orogens is sensitive to the deformation in the mantle part of the lithosphere, a point obscured in models that apply a boundary condition of constant basal heat flux within the mantle lithosphere. We show that for part of the plausible range of conductivities and heat source distributions within the continental lithosphere the maximum or potential temperatures in thickened continental crust typical of collision zones do not necessarily exceed the stability field of the high P-low T facies such as blueschists provided the mantle lithosphere is also thickened during the deformation. The appropriate range of parameters includes conductivities towards the upper limit of the plausible range ( k > ∼ 2.2 W m −1 K −1) together with low crustal heat production rates with distributions concentrating heat production in the upper crust, and relatively thin initial lithosphere. These observations suggest that at least some of the high P-low T assemblages found within continental orogens, for example in the Dalradian of the Scottish SW Highlands, may reflect the thermal response to whole lithospheric thickening and do not necessarily reflect thermal regimes attendent with subduction or unusually rapid excavation.