Predictor Of Metabolic Rate Research Articles

Flexible energy-saving strategies in female temperate-zone bats

Torpor is characterized by an extreme reduction in metabolism and a common energy-saving strategy of heterothermic animals. Torpor is often associated with cold temperatures, but in the last decades, more diverse and flexible forms of torpor have been described. For example, tropical bat species maintain a low metabolism and heart rate at high ambient and body temperatures. We investigated whether bats (Nyctalus noctula) from the cooler temperate European regions also show this form of torpor with metabolic inhibition at high body temperatures, and whether this would be as pronounced in reproductive as in non-reproductive bats. We simultaneously measured metabolic rate, heart rate, and skin temperature in non-reproductive and pregnant females at a range of ambient temperatures. We found that they can decouple metabolic rate and heart rate from body temperature: they maintained an extremely low metabolism and heart rate when exposed to ambient temperatures changing from 0 to 32.5 °C, irrespective of reproductive status. When we simulated natural temperature conditions, all non-reproductive bats used torpor throughout the experiment. Pregnant bats used variable strategies from torpor, to maintaining normothermy, or a combination of both. Even a short torpor bout during the day saved up to 33% of the bats' total energy expenditure. Especially at higher temperatures, heart rate was a much better predictor of metabolic rate than skin temperature. We suggest that the capability to flexibly save energy across a range of ambient temperatures within and between reproductive states may be an important ability of these bats and possibly other temperate-zone heterotherms.

The relationship between body temperature, heart rate, breathing rate, and rate of oxygen consumption, in the tegu lizard (Tupinambis merianae) at various levels of activity.

The present study determined whether EEG and/or EMG recordings could be used to reliably define activity states in the Brazilian black and white tegu lizard (Tupinambis merianae) and then examined the interactive effects of temperature and activity states on strategies for matching O2 supply and demand. In a first series of experiments, the rate of oxygen consumption (VO2), breathing frequency (fR), heart rate (fH), and EEG and EMG (neck muscle) activity were measured in different sleep/wake states (sleeping, awake but quiet, alert, or moving). In general, metabolic and cardio-respiratory changes were better indictors of the transition from sleep to wake than were changes in the EEG and EMG. In a second series of experiments, the interactive effects of temperature (17, 27 and 37 °C) and activity states on fR, tidal volume (VT), the fraction of oxygen extracted from the lung per breath (FIO2-FEO2), fH, and the cardiac O2 pulse were quantified to determine the relative roles of each of these variables in accommodating changes in VO2. The increases in oxygen supply to meet temperature- and activity-induced increases in oxygen demand were produced almost exclusively by increases in fH and fR. Regression analysis showed that the effects of temperature and activity state on the relationships between fH, fR and VO2 was to extend a common relationship along a single curve, rather than separate relationships for each metabolic state. For these lizards, the predictive powers of fR and fH were maximized when the effects of changes in temperature, digestive state and activity were pooled. However, the best r(2) values obtained were 0.63 and 0.74 using fR and fH as predictors of metabolic rate, respectively.

The utility of heart rate and minute ventilation as predictors of whole-body metabolic rate during occupational simulations involving load carriage

The utility of cardiac and ventilatory predictors of metabolic rate derived under temperate and heated laboratory conditions was evaluated during three fire-fighting simulations (70-mm hose drag, Hazmat recovery, bushfire hose drag; N = 16 per simulation). The limits of agreement for cardiac (temperate: − 0.54 to 1.77; heated: − 1.39 to 0.80 l min− 1) and ventilatory surrogates (temperate: − 0.19 to 1.27; heated: − 0.26 to 1.16 l min− 1) revealed an over-estimation of oxygen consumption that exceeded the acceptable limits required by occupational physiologists (N = 25; ± 0.24 l min− 1). Although ventilatory predictions offered superior precision during low-intensity work (P < 0.05), a cardiac prediction was superior during more demanding work (P < 0.05). Deriving those equations under heated conditions failed to improve precision, with the exception of the cardiac surrogate during low-intensity work (P < 0.05). These observations imply that individualised prediction curves are necessary for valid estimations of metabolic demand in the field.

Heart rate as a predictor of metabolic rate in heterothermic bats

While heart rate (fH) has been used as an indicator of energy expenditure, quantitative data showing the relationship between these variables are only available for normothermic animals. To determine whether fH also predicts oxygen consumption ( ) during torpor, we simultaneously measured , fH and subcutaneous body temperature (Tsub) of a hibernator, Gould's long-eared bats (Nyctophilus gouldi, 9 g, N=18), at ambient temperatures (Ta) between 0 and 25°C. At rest, fH of normothermic resting bats was negatively correlated with Ta, with maximum fH of 803 beats min(-1) (Ta=5°C). During torpor, the relationship between fH and Ta was curvilinear, and at low Tsub (~6°C), fH fell to a minimum average of 8 beats min(-1). The minimum average values for both and fH in torpor reported here were among the lowest recorded for bats. The relationship between fH and was significant for both resting (r(2)=0.64, P<0.001) and torpid bats (r(2)=0.84, P<0.001), with no overlap between the two states. These variables were also significantly correlated (r(2)=0.44, P<0.001) for entire torpor bouts. Moreover, estimates of from fH did not differ significantly from measured values during the different physiological states. Our study is the first to investigate the accuracy of fH as a predictor of during torpor and indicates the reliability of this method as a potential measure of energy expenditure in the field. Nevertheless, fH should only be used to predict within the range of activities for which robust correlations have been established.

Thermal optimum for pikeperch ( Sander lucioperca) and the use of ventilation frequency as a predictor of metabolic rate

Pikeperch is of increasing interest to the aquaculture industry, as a novel high value species. To our knowledge there is currently no information available on the metabolic rates of adult pikeperch. The present study determined the standard and maximum metabolic rates and ventilation frequency at six temperatures, ranging from 13 to 28 °C, in order to identify the temperature where pikeperch has the largest metabolic scope (MS). Between 13 and 25 °C, standard metabolic rates (SMR) increased as expected with a Q 10 = 1.8 in response to increasing temperatures, while maximum metabolic rate (MMR) did not change significantly within this temperature range. As a result, MS was not significantly affected by acclimation temperature between 13 and 25 °C. Above 25 °C, SMR increased significantly with a Q 10 = 2.5 while MMR declined, resulting in a decreased MS. In the present study, the maximum MS (MS MAX) was found at 18.8 °C. Defining the optimal temperature as the thermal range where fish can maintain 80% of MS MAX, shows that adult pikeperch have a broad thermal optimum between 10.4 and 26.9 °C. Since earlier studies on juvenile pikeperch have reported an optimal temperature range of 25–30 °C, we show that pikeperch have an ontogenetic shift in their thermal optimum, emphasizing the importance of considering fish size when deciding the temperature in aquaculture facilities. As a secondary objective we investigated whether gill ventilation frequency ( f V) could be used as an accurate predictor of oxygen consumption rate ( M ˙ O 2), during normoxia and progressive hypoxia. A strong correlation was found between f V and M ˙ O 2 across all temperatures, and f V could predict M ˙ O 2 with a high degree of accuracy in normoxia.

Guided Inquiry Lab Exercises in Development and Oxygen Consumption Using Zebrafish

Zebrafish have become a model organism in many areas of research and are now being used with more frequency in the classroom to teach important biological concepts. The two guided inquiry exercises in this article are each aimed at a different level of instruction, but each can be modified to fit the needs of many high school or college-level courses. The "Zebrafish Development and Environment" exercise teaches high school students about zebrafish development by presenting a series of embryos at different ages. Without access to visual references, students are asked to rank developing zebrafish by age and explain their choices. The students also learn about the heart and circulatory system and the effects of temperature on physiological processes. The second exercise, "Oxygen Consumption," is a 2-week laboratory designed for introductory college biology majors and involves the concept of oxygen consumption as a predictor of metabolic rate. During the first week of lab, students are introduced to the concept and learn how to measure oxygen consumption in zebrafish. In the second week, they perform an instructor-approved experiment of their own design, analyze the results using statistics, and write a report.

Assessment of cardiac output as a predictor of metabolic rate in rainbow trout

When water temperature was increased from 12 to 27°C at a rate of 2°C h−1, oxygen consumption of rainbow trout Oncorhynchus mykiss was correlated strongly with both heart rate and blood oxygen extraction but the relationship with cardiac output was variable and weak. On the other hand, when water temperature was decreased from 21 to 12°C at a rate of 0·5°C h−1, oxygen consumption was correlated with both heart rate and cardiac output but not with blood oxygen extraction. When fish were forced to swim increasingly faster, heart rate, cardiac output and blood oxygen extraction all correlated positively with oxygen consumption. For both cardiac output and heart rate, the slope of the regression line with oxygen consumption was elevated significantly more when the fish were forced to swim at increasingly higher swimming speeds than when water temperature was increased or decreased. The variation of the regression lines between cardiac output and oxygen consumption indicated that cardiac output presents few advantages over heart rate as a predictor of metabolic rate.

Assessment of cardiac output as a predictor of metabolic rate in rainbow trout

When water temperature was increased from 12 to 27°C at a rate of 2°C h−1, oxygen consumption of rainbow trout Oncorhynchus mykiss was correlated strongly with both heart rate and blood oxygen extraction but the relationship with cardiac output was variable and weak. On the other hand, when water temperature was decreased from 21 to 12°C at a rate of 0·5°C h−1, oxygen consumption was correlated with both heart rate and cardiac output but not with blood oxygen extraction. When fish were forced to swim increasingly faster, heart rate, cardiac output and blood oxygen extraction all correlated positively with oxygen consumption. For both cardiac output and heart rate, the slope of the regression line with oxygen consumption was elevated significantly more when the fish were forced to swim at increasingly higher swimming speeds than when water temperature was increased or decreased. The variation of the regression lines between cardiac output and oxygen consumption indicated that cardiac output presents few advantages over heart rate as a predictor of metabolic rate.

The limitations of heart rate as a predictor of metabolic rate in fish

The limitations of heart rate as a predictor of metabolic rate in fish

The limitations of heart rate as a predictor of metabolic rate in fish

Although telemetered heart rate (fH) has been used as a physiological correlate to predict the metabolic rate (as oxygen consumption, V̇O2) of fish in the field, it is our contention that the method has not been validated adequately for fish. If fH in fish is to be used to estimate V̇O2, a single linear (or log‐linear) relationship must be established for each species between the two variables which allows V̇O2 to be predicted accurately under all environmentally relevant conditions. Our analyses of existing data indicate that while a good linear (or log‐linear) relationship can be established between fH and V̇O2, the conditions under which the relationship applies may be quite restricted. Physiological states and environmental factors affect the relationship between fH and V̇O2 significantly such that several curves can exist for a single species. In addition, there are situations in which fH and V̇O2 do not covary in a significant manner. In some situations fH can vary over much of its physiological range while V̇O2 remains constant; in others V̇O2 may vary while fH is invariate. The theoretical basis for this variability is examined to explain why the use of telemetered fH in predicting V̇O2 of fish may be limited to certain specified applications.

Gaseous Metabolism of Leghorns and Broilers during Early Growth: Resting Metabolic Rate , ,

Resting metabolic rate (RMR) was measured in male DeKalb 231 × Cornell White Leghorns and Ross × Arbor Acre broiler chicks 0–8 weeks-of-age in a modified Haldane apparatus. Chicks were fed a broiler starter diet containing 22% protein and 3234 kcal/kg metabolizable energy (ME). All determinations were conducted between 0800 and 1200 hr. Feed and water were available ad libitum and lighting was continuous.Metabolic rate (kcal/bird per day) was plotted against body weight for the entire 8-week period and results were analyzed using analysis of covariance. RMR in both broilers and Leghorns was best described by the equation Y = 137.87 W·77 where Y equals kcal/bird-day and W equals weight in kg. RMR of Leghorns was 23% higher over the entire 8-week period. The RMR of broilers was 30% higher than their BMR for week 1 and averaged 18% higher over the entire 8-week period.Body composition and gut content were determined on broilers and Leghorns at weekly intervals for 8 weeks. Body weight of birds used to determine RMR were then corrected for percent fat, moisture, ash, protein, and gut content. Corrected body weights were plotted against RMR to determine which body component was the best predictor of metabolic rate. As the body weight was reduced by correcting for the various components, the slope changed little, while the constant of proportionality increased. Live weight and empty body weight (body weight minus gut content) yielded the highest slope. All equations had high coefficients of correlation, greater than .94.