Thermoregulation in rapid growing broiler chickens is compromised by constraints on radiative and convective cooling performance

Broiler chickens are selected to undergo a rapid six-week hatch-to-slaughter growth phase to attain large body and muscle mass. Broilers have relatively high resting and locomotor metabolic costs suggesting that adaptive thermoregulatory mechanisms are required to dissipate excess heat. Using thermal imaging in the growing broiler we characterised the trajectory of radiative and convective cooling in still air across broiler development. Scaling of head, tarsus and toe surface area did not deviate from body mass^2/3 while torso area increased with positive allometry, body mass^0.82, reflecting increased feather coverage and/or disproportionate abdominal/thoracic growth. Despite relatively increased area, the body became less effective for heat transfer presumably due to increasing feather coverage. Conversely, the magnitude of heat exchange from the distal hindlimbs was improved in larger birds. Overall capacity to transfer heat by convection and radiation in still air was attenuated over development, since the proportion of resting metabolic rate accounted for decreased in standing and sitting postures. This physiological constraint could be ameliorated by increased latent heat transfer or provision of environmental ventilation, which we modelled according to industrial guidelines. Based on models, higher airspeeds coincided with improved convective cooling that assisted in maintaining the proportion of RMR accounted for by convective and radiative heat transfer. These data highlight the potentially adverse thermoregulatory effects of rapid growth rate and body mass increases, which may contribute to the increased sedentary resting and decreased locomotor behaviour observed in large broilers.     

Convective heat transfer from a nude body under calm conditions: assessment of the effects of walking with a thermal manikin

The present experimental work is dedicated to the analysis of the effect of walking on the thermal insulation of the air layer (I _a ) and on the convective heat transfer coefficients (h _conv ) of the human body. Beyond the standing static posture, three step rates were considered: 20, 30 and 45 steps/min. This corresponds to walking speeds of approximately 0.23, 0.34 and 0.51 m/s, respectively. The experiments took place in a climate chamber with an articulated thermal manikin with 16 independent parts. The indoor environment was controlled through the inner wall temperatures since the objective of the tests was restricted to the influence of the walking movements under calm conditions. Five set points were selected: 10, 15, 20, 25 and 30°C, and the operative temperature within the test chamber varied between 11.9 and 29.6°C. The highest and lowest I _a values obtained were equal to 0.87 and 0.71 clo, respectively, and the reduction in insulation due to walking ranged between 9.8 and 11.5%. The convective coefficients (h _conv ) for the whole body and for the different body segments were also determined for each step rate. In the case of the whole body, for the standing static reference posture, the mean value of h _conv was equal to 3.3 W/m²°C and a correlation [Nu = Nu(Gr)] for natural convection is also presented in good agreement with previous results. For the other postures, the values of h _conv were equal to 3.7, 3.9 and 4.2 W/m²°C, respectively for 20, 30 and 45 steps/min.     

Thermal resistance parameters of the air environment at various altitudes

 The thermal properties of atmospheric air surrounding the human body at various altitudes are characterized with a system of parameters. This system comprises resistance of the air to convective heat transfer h _c ^–1, °C (W/m²)⁻¹ and to water vapour transfer h _D ^–1, s/m. The concept of ’evaporative resistance’h _e ^–1, hPa (W/m²)⁻¹) following the similarity of the processes is introduced. In obtaining the altitude dependencies of investigated paramters, a respective heat transfer equation expressing the rate of heat exchange at the boundary body surface – ambient air is applied. The use of the body thermal state of the established altitude dependencies is discussed. The concept of ’thermal stability’ related to the evaporative resistance parameter h _e ^–1 is introduced. This parameter is assumed as: (1) an indicator of the human body thermal stability and (2) distributor and predictor of environmental influence on the body thermal state. Received: 5 January 1996 / Accepted 5 November 1996     

Heat and mass exchange processes between the surface of the human body and ambient air at various altitudes

 The rates of convection and evaporation at the interface between the human body and the surrounding air are expressed by the parameters convective heat transfer coefficient h _c, in W m^–2°C^–1 and evaporative heat transfer coefficient h _e, W m^–2 hPa^–1. These parameters are determined by heat transfer equations, which also depend on the velocity of the airstream around the body, that is still air (free convection) and moving air (forced convection). The altitude dependence of the parameters is represented as an exponential function of the atmospheric pressure p: h _c∼p ⁿ and h _e∼p ^1–n, where n is the exponent in the heat transfer equation. The numerical values of n are related to airspeed: n=0.5 for free convection, n=0.618 when airspeed is below 2.0 ms^–1 and n=0.805 when airspeed is above 2.0 ms^–1. This study considers the coefficients h _c and h _e with respect to the similarity of the two processes, convection and evaporation. A framework to explain the basis of established relationships is proposed. It is shown that the thickness of the boundary layer over the body surface increases with altitude. As a medium of the transfer processes, the boundary layer is assumed to be a layer of still air with fixed insulation which causes a reduction in the intensity of heat and mass flux propagating from the human body surface to its surroundings. The degree of reduction is more significant at a higher altitude because of the greater thickness of the boundary layer there. The rate of convective and evaporative heat losses from the human body surface at various altitudes in otherwise identical conditions depends on the following factors: (1) during convection – the thickness of the boundary layer, plus the decrease in air density, (2) during evaporation (mass transfer) – the thickness of the boundary layer, plus the increase with altitude in the diffusion coefficient of water vapour in the air. The warming rate of the air volume due to convection and evaporation is also considered. Expressions for the calculation of altitude dependences h _c (p) and h _e (p) are suggested. Received: 23 June 1998 / Accepted: 10 February 1999     

Estimation of cardiac output and stroke volume from thermal equilibration and heartbeat rates in fish

Cardiac output and stroke volume were estimated for a 200 g largemouth blackbass (Micropterus salmoides) by a modified whole-body thermodilution method using the relation between thermal equilibration rates and heartbeat frequencies. The reciprocal of the thermal time constant, k (min^–1), was related to the heartbeat frequency, F (beats min^–1), by the equation k=0.00146 F + 0.309; the slope is the weight-specific stroke volume (ml g^–1) and the intercept is the weight-specific heat transfer constant (cal °C^–1 min^–1 g^–1). Stroke volume was 0.292 ml (0.00146 ml/g body weight), yielding cardiac output values ranging from 44 ml kg^–1 min^–1 (at 30 beats min) to 158 ml kg^–1 min^–1 (at 108 beats min^–1), or 4.4 to 15.8% of body weight. Active (convective) heat transfer due to blood flow constituted an estimated 11 to 34% (mean 22.5%) of total heat transfer, depending on heartbeat frequency; this variability constitutes physiological thermoregulation.     

Effects of saturated fatty acids on amylase release from exocrine pancreatic segments of sheep,rats, hamsters,field voles and mice

 Stimulatory effects of saturated fatty acids consisting of 4 (butyrate), 8 (octanoate), 12 (laurate) and 16 (palmitate) carbon atoms, as well as acetylcholine on pancreatic amylase release were assessed in tissue segments isolated from sheep, rats, hamsters, field voles and mice. The amount of amylase release induced by the fatty acids (1 μmol ⋅ l^-1 to 10 mml ⋅ l^-1) and by acetylcholine (10 nmol ⋅ l^-1 to 100 μmol ⋅ l^-1) increased in a concentration-dependent manner, and the maximum response in response to the fatty acids was obtained at the maximal dose used. The maximum increase in amylase release in response to butyrate or octanoate was highly and significantly (r=0.974, P<0.001) dependent on the log value of the mean body mass in the following order: sheep>rats>hamsters>field voles>mice. On the other hand, the response to laurate and palmitate was variable among animal species. Addition of atropine (1.4 μmol ⋅ l^-1) to the medium did not reduce the responses to octanoate stimulation, but significantly reduced acetylcholineinduced responses, implying that the effects of the fatty acids were not mediated through activation of muscarinic acetylcholine receptors. Reduction of calcium ion concentration in the medium significantly inhibited the responses induced by the fatty acids and acetylcholine, suggesting that amylase release depends on extracellular calcium ions. Accepted: 14 May 1996     

Octanoate increases cytosolic Ca2+ concentration and membrane conductance in ovine pancreatic acinar cells

 In order to investigate the cellular mechanisms involved in amylase release in response to stimulation with short-chain fatty acids, changes in intracellular calcium concentration ([Ca²⁺]_i), membrane current and amylase release were measured in pancreatic acinar cells of sheep. Both octanoate and acetylcholine raised [Ca²⁺]_i in acinar cells in a concentration-dependent manner. The rise in [Ca²⁺]_i in response to the stimulation with octanoate (10 mmol ⋅ l^-1) was reduced in a medium without CaCl₂, but was markedly enhanced by reintroduction of CaCl₂ into the medium up to 2.56 mmol ⋅ l^-1. Perfusion of the cells with a medium containing octanoate (5 mmol ⋅ l^-1) or acetylcholine (0.5 μmol ⋅ l^-1) immediately raised inward current across the cell membrane at a holding-membrane potential of −30 mV. The inward current became greater as the holding potential became more negative. The equilibrium potential was 1.8 mV and 3.9 mV for octanoate and acetylcholine, respectively, being consistent with that for Cl^-. Although intracellular application of octanoate through a patch-clamp pipette also raised inward current after several minutes in some cells (4 out of 12), this possibility was significantly smaller than that for extracellular application. In other cells, even though the intracellular application of octanoate did not cause an increase in current, it always caused responses immediately after introduction of the fatty acid into the medium. Stimulation with fatty acid as well as acetylcholine raised amylase release in a concentration-dependent manner in cells dispersed from tissue segments with crude collagenase and trypsin inhibitor. Without trypsin inhibitor, crude collagenase significantly and selectively reduced the octanoate (10 mmol ⋅ l^-1)-induced amylase release. Dispersion with crude collagenase and trypsin significantly reduced both responses induced by octanoate and acetylcholine (5.5 μmol ⋅ l^-1). We conclude that fatty acids and acetylcholine increase [Ca²⁺]_i, which consequently evokes a rise in transmembrane ion (Cl^-) conductance and amylase release, and that trypsin-sensitive protein(s) in the cell membrane are involved in secretory processes activated by stimulation with fatty acids in ovine pancreatic acinar cells. Accepted: 14 May 1996     

Biomass, production and heterotrophic activity of bacterioplankton in the Great Astrolabe Reef lagoon (Fiji)

 Biomass, production and heterotrophic activity of bacterioplankton were determined for two weeks in the Great Astrolabe Reef lagoon, Fiji. Bacterial and Bacterial activities were distributed homogeneously throughout the water column (20 to 40 m deep) and varied little from site to site inside the lagoon. Bacterioplankton biomass and production also varied little over a diel period with coefficients of variation of 9 and 22%, respectively. On average, over the whole study, bacterial abundance was 0.77×10⁹ cells l^-1 and bacterial production averaged 0.36 μg-at. C l^-1 d^-1. Bacterial abundance and production were greater in the lagoon than in oceanic waters. Attachment to particles seems to provide an advantage for bacterioplankton growth because specific growth rates for attached bacterioplankton were, on average, significantly greater than that of the free community. Growth efficiency, determined by correlating the net increase of bacterial biomass and the net decrease of dissolved organic carbon (DOC) in dilution cultures, was very low (average 6.6%). Using carbon growth efficiency and bacterial production rates, heterotrophic activity was estimated to average 5.4 μg-at. C l^-1 d^-1. The turn-over rate of DOC (average 114 μg-at. C l^-1) due to bacterial consumption was estimated to be 0.048 d^-1 during the period of study. Accepted: 25 July 1998     

Kinetic coefficients for simultaneous reduction of sulfate and uranium by Desulfovibrio desulfuricans

 Previously it was demonstrated that bacteria are capable of transforming soluble uranyl ion, U(VI), to insoluble uraninite, U(IV); however, the rate for this transformation has not been determined. We report the kinetic coefficients for Desulfovibrio desulfuricans DSM 1924 grown in a continuous-flow chemostat where pyruvate was the electron donor and sulfate was the electron acceptor. The medium was supplemented with 1 mM uranyl nitrate, and the chemostat flow rate ranged from 1.12 ml/h to 4.75 ml/h with incubation at 28°C. The maximum rate of pyruvate utilization (k) was determined to be 4.7 days^-1, while the half-velocity constant (K _s) was 127 mg/l. The yield coefficient (Y) of cells per mole of pyruvate oxidized was calculated to be 0.021 g, while the endogenous decay coefficient (k _d) was determined to be 0.072 days^-1. More than 90% of U(VI) was transformed to U(VI) in the chemostat under the conditions employed. Received: 7 September 1995/Received last revision: 10 January 1996/Accepted: 5 February 1996     

Shinrin-yoku (forest-air bathing and walking) effectively decreases blood glucose levels in diabetic patients

 The influence of ”shinrin-yoku” (forest-air bathing and walking) on blood glucose levels in diabetic patients was examined. Eighty-seven (29 male and 58 female) non-insulin-dependent diabetic patients [61 (SEM 1) years old] participated in the present study. Shinrin-yoku was performed nine times over a period of 6 years. The patients were divided into two parties. They then walked in the forest for 3 km or 6 km according to their physical ability and/or the existence of diabetic complications. The mean blood glucose level after forest walking changed from 179 (SEM 4) mg · 100 ml^–1 to 108 (SEM 2) mg · 100 ml^–1 (P<0.0001). The level of glycated haemoglobin A_1c also decreased from 6.9 (SEM 0.2)% (before the first shinrin-yoku) to 6.5 (SEM 0.1)% (after the last shinrin-yoku; P<0.05). Blood glucose values declined by 74 (SEM 9) mg · 100 ml^–1 and 70 (SEM 4) mg · 100 ml^–1 after short- and long-distance walking respectively. There was no significant difference between these values. Since the forest environment causes changes in hormonal secretion and autonomic nervous functions, it is presumed that, in addition to the increased calorie consumption and improved insulin sensitivity, walking in a forest environment has other beneficial effects in decreasing blood glucose levels. Received: 9 July 1997/Accepted: 20 October 1997     

Use of an industrial effluent as a carbon source for denitrification of a high-strength wastewater

Denitrification of a high-strength synthetic wastewater (150 g NO^- ₃ l^-1) was carried out using a wine distillery effluent as an example of an industrial carbon source (22.7 g chemical oxygen demand l^-1). Two configurations were tested: one consisted of an acidogenesis reactor followed by a denitrifying reactor and the other was a single reactor directly fed with the raw effluents. In both cases, denitrification was achieved at a nitrate load of 9.54 g NO^- ₃ l^-1 day^-1 (2.19 g N as NO^- ₃ l^-1 day^-1) with good specific reduction rates: 32.6 mg and 35.2 mg N as NO _x  g volatile suspended solids h^-1, calculated on a single day, for the two-step and the one-step process respectively. Dissimilatory nitrate reduction to ammonium did not occur, even in the one-step process. Received: 26 October 1995/Received revision: 15 February 1996/Accepted: 20 February 1996     

Wind-chill-equivalent temperatures: regarding the impact due to the variability of the environmental convective heat transfer coefficient

The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published “new” WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a “gold standard” for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized.     

Observations on the thermal conductance of Adélie (Pygoscelis adeliae) and Humboldt (Spheniscus humboldti) penguins

 Analyses of cooling rates in one Adélie and one Humboldt penguin yielded calculated thermal conductance values of 0.1040 and 0.1672 W(kg ^°C)^-1, respectively. We review the methods used to calculate penguin surface area, an important component in calculating conductance values, and suggest that, in comparative studies of thermal balance, the use of body mass is a better estimator of body size than surface area. Using previously published data on penguin species, we found a significant model to predict thermal conductance from body mass according to: log C= log 0.1083−0.474 log M, where C is minimal specific thermal conductance in W(kg ^°C)^-1 and M is body mass in kilograms. Received: 13 June 1995/Accepted: 11 March 1996     

Effect of ferrous iron concentration on the catalytic activity of immobilized cells of Thiobacillus ferrooxidans

 The kinetics of continuous oxidation of ferrous iron by immobilized cells of Thiobacillus ferrooxidans was studied in a packed-bed bioreactor. Polyurethane foam biomass support particles were used as carriers for cell immobilization. Effects of ferrous iron concentration and its volumetric loading on the kinetics of the reaction were investigated. Media containing different concentrations of ferrous iron in the range 5–20 kg m^-3 were tested. For each medium the kinetics of the reaction at different volumetric loadings of ferrous iron, at a constant temperature of 30^°C, were determined. With media containing 5 kg m^-3 and 10 kg m^-3 Fe²⁺, the fastest oxidation rates of 34.25 kg m^-3 h^-1 and 32 kg m^-3 h^-1 were achieved at a dilution rate of around 6 h^-1, which represents a residence time of 10 min. Employing a higher concentration of ferrous iron (20 kg m^-3) in the medium resulted in lower oxidation rates, with a maximum value of 10 kg m^-3 h^-1, indicating an inhibitory effect of ferrous iron on growth and activity of T. ferrooxidans. The reliable performance of the bioreactor during the course of the experiments confirmed the suitability of polyurethane foam biomass support particles as carriers for T. ferrooxidans immobilization. Received: 5 December 1995/Received revision: 21 April 1996/Accepted: 29 April 1996     

Sulfated extracellular polysaccharide production by the halophilic cyanobacterium Aphanocapsa halophytia immobilized on light-diffusing optical fibers

 The cyanobacterium, Aphanocapsa halo-phytia MN-11, was immobilized in calcium alginate gel and coated on light-diffusing optical fibers (LDOF) for sulfated extracellular polysaccharide production. Results indicated that sulfated extracellular polysaccharide production depends on the number of immobilized cells and the light intensity. In addition, the production rate reached 116.0 mg (mg dry cells)^-1 day^-1 when the cells that were immobilized on LDOF were incubated under a light intensity of 1380 cd sr m^-2 at a cell concentration of 1.0×10⁸ cells/cm³ gel. Cells immobilized on LDOF produced about ten times more sulfated extracellular polysaccharide than those immobilized in calcium alginate beads only (11.7 mg(mg dry cells)^-1day^-1). Received: 31 March 1995/Revised last revision 12 June 1995/Accepted 26 July 1995     

Effect of temperature difference between manikin and wet fabric skin surfaces on clothing evaporative resistance: how much error is there?

Clothing evaporative resistance is one of the inherent factors that impede heat exchange by sweating evaporation. It is widely used as a basic input in physiological heat strain models. Previous studies showed a large variability in clothing evaporative resistance both at intra-laboratory and inter-laboratory testing. The errors in evaporative resistance may cause severe problems in the determination of heat stress level of the wearers. In this paper, the effect of temperature difference between the manikin nude surface and wet textile skin surface on clothing evaporative resistance was investigated by both theoretical analysis and thermal manikin measurements. It was found that the temperature difference between the skin surface and the manikin nude surface could lead to an error of up to 35.9% in evaporative resistance of the boundary air layer. Similarly, this temperature difference could also introduce an error of up to 23.7% in the real clothing total evaporative resistance (R _{et_real}  < 0.1287 kPa m²/W). Finally, it is evident that one major error in the calculation of evaporative resistance comes from the use of the manikin surface temperature instead of the wet textile fabric skin temperature.     

Picophytoplankton biomass, community structure and productivity in the Great Astrolabe Lagoon, Fiji

 Phytoplankton biomass, community structure and productivity of the Great Astrolabe lagoon and surrounding ocean were studied using measurements of chlorophyll concentration and carbon uptake. The contribution of picophytoplankton to biomass, productivity and community structure was estimated by size fractionation, ¹⁴C-incubation and flow cytometry analysis. Picoplankton red fluorescence was demonstrated to be a proxy for chlorophyll <3 μm. Consequently, the percentage contribution to chl a<3 μm from each picoplankton group could be calculated using regression estimated values of ψ _i (fg chl a per unit of red fluorescence). In the lagoon, average chlorophyll concentration was 0.8 mg m^-3 with 45% of phytoplankton <3 μm. Primary production reached 1.3 g C m^-2 day^-1 with 53% due to phytoplankton <3 μm. Synechococcus was the most abundant group at all stations, followed by Prochlorococcus and picoeukaryotes. At all stations, Prochlorococcus represented less than 4% of the chl a <3 μm, Synechococcus between 85 and 95%, and Picoeukaryotes between 5 and 10%. In the upper 40 m of surrounding oceanic waters, phytoplankton biomass was dominated by the >3 μm size fraction. In deeper water, the <1 μm size fraction dominated. Prochlorococcus was the most abundant picoplankton group and their contributions to the chlorophyll a<3 μm were close to that of the picoeukaryotes (50% each). Accepted: 27 May 1999     

Nitrogen and energy requirements of the short-tailed fruit bat (Carollia perspicillata): fruit bats are not nitrogen constrained

 Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3–1.8 times their body mass ⋅ day^-1 and ingested 1339.5–1941.4 kJ ⋅ kg^-0.75 ⋅ day^-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively), but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ ⋅ kg^-0.75 ⋅ day^-1 or 58.6 kJ ⋅ . Metabolic fecal N and endogenous urinary N losses were 0.87 mg N ⋅ g^-1 dry matter intake and 172.5 mg N ⋅ kg^-0.75 ⋅ day^-1, respectively, and bats required 442 mg N ⋅ kg^-0.75 ⋅ day^-1 (total nitrogen) or 292.8 mg N ⋅ kg^-0.75 ⋅ day^-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets. Accepted: 23 June 1996     

Continuous production of ethanol using yeast cells immobilized in preformed cellulose beads

 Saccharomyces cerevisiae cells were immobilized on preformed cellulose beads by adsorption. The fermentation capacity of the immobilized yeast cells was found to be practically independent of the hydrogen ion concentration between pH 3.1 and 6.25. The fermentation capacity was maximal at 30 °C. The immobilized yeast cells were used for continuous production of ethanol in a fluidized-bead reactor. The average values characteristic for the process were an ethanol concentration of 41.9±0.1 g l^-1, a fermentation efficiency of 82.9±2.1% and a volumetric productivity of 3.94±0.52 g l^-1 h^-1. Received: 9 October 1995/Accepted: 22 April 1996