Partitioning of late gestation energy expenditure in ewes using indirect calorimetry and a linear regression approach

Abstract

Late gestation energy expenditure (EE_gest) originates from energy expenditure (EE) of development of conceptus (EE_conceptus) and EE of homeorhetic adaptation of metabolism (EE_homeorhetic). Even though EE_gest is relatively easy to quantify, its partitioning is problematic. In the present study metabolizable energy (ME) intake ranges for twin-bearing ewes were 220 – 440, 350 – 700, 350 – 900 kJ per metabolic body weight (W^0.75) at week seven, five, two pre-partum respectively. Indirect calorimetry and a linear regression approach were used to quantify EE_gest and then partition to EE_conceptus and EE_homeorhetic. Energy expenditure of basal metabolism of the non-gravid tissues (EE_bmng), derived from the intercept of the linear regression equation of retained energy [kJ/W^0.75] and ME intake [kJ/W^0.75], was 298 [kJ/W^0.75]. Values of the intercepts of the regression equations at week seven, five, and two pre-partum were 311, 398, and 451 [kJ/W^0.75], respectively. The difference between the intercepts for different weeks was used to calculate EE_homeorhetic. The remaining part of EE_gest was considered to be EE_conceptus. In conclusion, the good agreement between our values of EE_conceptus and those in the literature indicates the method's validity.     

Effect of undernutrition in foetal life on energy expenditure during gestation in ewes

The long-term effect of early life undernutrition on late gestation energy expenditure (EEgest) was investigated in sheep. Ewes were fed either adequate (100%) or restricted (60%) energy and protein during late foetal life as well as during last trimester of gestation later in life, resulting in three groups: Adequate-Adequate (AA, n = 5), Adequate-Restricted (AR, n = 5) and Restricted-Restricted (RR, n = 5). At two weeks pre-partum, EEgest were calculated from respiratory gaseous exchange and nitrogen excreted in urine and further it was partitioned to energy expenditure for conceptus development (EEconceptus) and homeorhetic adaptations in maternal metabolism (EEhomeorhetic). Late gestational energy and protein restriction reduced the EEgest in the AR ewes (4.1 MJ x d(-1)) but not in the RR ewes (5.2 MJ x d(-1)) compared with the AA ewes (6.8 MJ x d(-1)). Based on conceptus-weight, no significant difference was found in EEhomeorhetic among the groups; 172, 175 and 169 kJ/kg x d(-1) in AA, AR and RR ewes, respectively. However, EEconceptus was significantly lower in AR (135 kJ/kg x d(-1)) in comparison with AA (298 kJ/kg x d(-1)) and RR (252 kJ/kg x d(-1)) ewes. In conclusion, exposure nutrient restriction in early life impairs the ability of ewes to respond to nutritional restriction in terms of energy expenditure of gestation.     

Estimation of activity related energy expenditure and resting metabolic rate in freely moving mice from indirect calorimetry data

Physical activity (PA) is a main determinant of total energy expenditure (TEE) and has been suggested to play a key role in body weight regulation. However, thus far it has been challenging to determine what part of the expended energy is due to activity in freely moving subjects. We developed a computational method to estimate activity related energy expenditure (AEE) and resting metabolic rate (RMR) in mice from activity and indirect calorimetry data. The method is based on penalised spline regression and takes the time dependency of the RMR into account. In addition, estimates of AEE and RMR are corrected for the regression dilution bias that results from inaccurate PA measurements. We evaluated the performance of our method based on 500 simulated metabolic chamber datasets and compared it to that of conventional methods. It was found that for a sample time of 10 minutes the penalised spline model estimated the time-dependent RMR with 1.7 times higher accuracy than the Kalman filter and with 2.7 times higher accuracy than linear regression. We assessed the applicability of our method on experimental data in a case study involving high fat diet fed male and female C57Bl/6J mice. We found that TEE in male mice was higher due to a difference in RMR while AEE levels were similar in both groups, even though female mice were more active. Interestingly, the higher activity did not result in a difference in AEE because female mice had a lower caloric cost of activity, which was likely due to their lower body weight. In conclusion, TEE decomposition by means of penalised spline regression provides robust estimates of the time-dependent AEE and RMR and can be applied to data generated with generic metabolic chamber and indirect calorimetry set-ups.     

Reducing the time period of steady state does not affect the accuracy of energy expenditure measurements by indirect calorimetry.

Achievement of steady state during indirect calorimetry measurements of resting energy expenditure (REE) is necessary to reduce error and ensure accuracy in the measurement. Steady state is often defined as 5 consecutive min (5-min SS) during which oxygen consumption and carbon dioxide production vary by +/-10%. These criteria, however, are stringent and often difficult to satisfy. This study aimed to assess whether reducing the time period for steady state (4-min SS or 3-min SS) produced measurements of REE that were significantly different from 5-min SS. REE was measured with the use of open-circuit indirect calorimetry in 39 subjects, of whom only 21 (54%) met the 5-min SS criteria. In these 21 subjects, median biases in REE between 5-min SS and 4-min SS and between 5-min SS and 3-min SS were 0.1 and 0.01%, respectively. For individuals, 4-min SS measured REE within a clinically acceptable range of +/-2% of 5-min SS, whereas 3-min SS measured REE within a range of -2-3% of 5-min SS. Harris-Benedict prediction equations estimated REE for individuals within +/-20-30% of 5-min SS. Reducing the time period of steady state to 4 min produced measurements of REE for individuals that were within clinically acceptable, predetermined limits. The limits of agreement for 3-min SS fell outside the predefined limits of +/-2%; however, both 4-min SS and 3-min SS criteria greatly increased the proportion of subjects who satisfied steady state within smaller limits than would be achieved if relying on prediction equations.     

Relationship between plasma progesterone in late gestation and the incidence of dystocia in romney ewes

Thirty-eight percent (6 16 ) of the ewes with a previous history of dystocia and 15% (2 13 ) of the ewes with no dystocia in 4 lambings, had difficult births in 1976. Despite large variations in plasma progesterone concentrations among ewes at the same stage of gestation there were no differences in the progesterone concentration during the last 30 days of gestation for both single- and twin-bearing ewes with or without a history of dystocia, nor for single-bearing ewes with or without a dystocia. The progesterone concentrations declined during the last 10 days before parturition in ewes with and without dystocia. The lambs from single-bearing ewes with a dystocia did not have heavier birth weights than the lambs from single-bearing ewes without a dystocia.     

An energy 'sources' and 'fractions' approach to the mechanical energy expenditure problem--III. Mechanical energy expenditure reduction during one link motion

Mechanical energy economy and transformation during one link motion are analyzed on the basis of the theory developed in the previous publications (parts I and II of this series, J. Biomechanics 19, 287-300). The 'compensation coefficient' characterizing mechanical energy economy is introduced. The attempts to estimate MEE using only energy curves and neglecting the powers of real sources of energy implicitly lead to replacement of real force and moment systems by the systems reduced to the centers of mass. But such an unintentional substitution of imaginary sources for real ones, specifically, the reduction of forces acting on the link to the equivalent system, changes estimates of mechanical energy expenditure (MEE). That is why the methods of calculating MEE economy based on the determination of so-called 'quasi-mechanical' work (the sum of the kinetic and potential energy increases per one cycle of motion) are not correct. There are two mechanisms to reduce the MEE using the antiphase fluctuations (corresponding to energy transformations) of the (a) rotational and translational fractions of the total energy (at the expense of the F-sources); (b) potential and kinetic energies (at the expense of the mg-source).     

An energy 'sources' and 'fractions' approach to the mechanical energy expenditure problem--V. The mechanical energy expenditure reduction during motion of the multi-link system

Mechanical energy economy during motion of the multi-link system is analyzed on the basis of the theory developed in the previous publications (parts I-IV of this series, J. Biomechanics 19, 287-309). The compensation coefficients for the F- and M-sources and also the absolute compensation coefficient reflecting the mechanical energy economy due to four possible resources are introduced. These resources are the antiphase fluctuations of (I) each link's total energy fractions involving energy transformations between (1) rotational and translational fractions by F-sources, (2) kinetic and potential fractions by mg-source; (II) the links' total energies involving energy transfers between (3) links by F-sources, (4) links by M-sources. The conditions of mechanical energy economy, particularly due to M-sources, are analyzed.     

Using direct calorimetry to test the accuracy of indirect calorimetry in an ectotherm

We previously demonstrated that the relationship between respiratory gas exchange and metabolic heat production is unexpectedly variable and that conventional approaches to estimating energy expenditure by indirect calorimetry can incorporate large errors. Prior studies, however, comparing direct and indirect calorimetry of animals focused only on endothermic organisms. Given that endothermy and ectothermy represent a fundamental dichotomy of animal energetics, in this analysis we explore how these contrasting physiologies correlate with the relationship between heat production and respiratory gas exchange. Simultaneous indirect and direct calorimetry in an ectotherm, the ball python (Python regius Shaw), revealed that the relationships between gas exchange and heat production were within 1% of those expected when analyses using indirect calorimetry were based on the assumption that the fasting animal catabolized only protein. This accuracy of indirect calorimetry contrasts sharply with our previous conclusions for three species of birds and mammals.     

Estimation of daily energy expenditure in pregnant and non-pregnant women using a wrist-worn tri-axial accelerometer

Background

Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE) in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK) to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability.

Methods

Non-pregnant (N = 73) and pregnant (N = 35) Swedish women (aged 20–35 yrs) wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE) was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22–65 yrs) wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable).

Results

There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR) acceptability of wrist and hip placement was 9(8–10) and 9(7–10), respectively; there was a within-individual difference of 0.47 (p<.001).

Conclusions

A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.     

Estimation of resistance exercise energy expenditure using triaxial accelerometry

Recently, it was demonstrated that a uniaxial accelerometer worn at the hip could estimate resistance exercise energy expenditure. As resistance exercise takes place in more than 1 plane, the use of a triaxial accelerometer may be more effective in estimating resistance exercise energy expenditure. The aims of this study were to estimate the energy cost of resistance exercise using triaxial accelerometry and to determine the optimal location for wearing triaxial accelerometers during resistance exercise. Thirty subjects (15 men and 15 women; age = 21.7 ± 1.0 years) performed a resistance exercise protocol consisting of 2 sets of 8 exercises (10RM loads). During the resistance exercise protocol, subjects wore triaxial accelerometers on the wrist, waist, and ankle; a heart rate monitor; and a portable metabolic system. Net energy expenditure was significantly correlated with vertical (r = 0.67, p < 0.001), horizontal (r = 0.43, p = 0.02), third axis (r = 0.36, p = 0.048), and sum of 3 axes (r = 0.50, p = 0.005) counts at the waist, and horizontal counts at the wrist (r = -0.40, p = 0.03). Regression analysis using fat-free mass, sex, and the sum of accelerometer counts at the waist as variables was used to develop an equation that explained 73% of the variance of resistance exercise energy expenditure. A triaxial accelerometer worn at the waist can be used to estimate resistance exercise energy expenditure but appears to offer no benefit over uniaxial accelerometry. The use of accelerometers in estimating resistance exercise energy expenditure may prove useful for individuals and athletes who participate in resistance training and are focused on maintaining a tightly regulated energy balance.     

The anaerobic energy metabolism of goldfish determined by simultaneous direct and indirect calorimetry during anoxia and hypoxia

Summary The energy flow of the anaerobic metabolism of glodfish at 20°C during hypoxia and anoxia was studied by simultaneous direct and indirect calorimetry. During anoxia the heat production as determined by direct calorimetry (180 J · h^–1 · kg^–0.85) is reduced to 30% of the normoxic level (570 J · h^–1 · kg^–0.85), which is the same reduction as found previously. The patterns of substrate utilization are compared with previous results, where the anoxic pattern was established by simultaneous calorimetry without carbon dioxide measurements. The present results, which do include carbon dioxide measurements, show the same pattern: carbohydrate and protein as substrates and carbon dioxide, ethanol and fat as end products. The pattern of substrate utilization at low oxygen levels is a combination of the anoxic pattern with an aerobic component. During anoxia only 5% of the metabolizable energy is used for energy metabolism. Of the remaining part (metabolizable energy for production) 60% is converted into ethanol and 40% into fat. At two hypoxia levels the distribution of the metabolizable energy for production into ethanol and fat is the same.     

Selfish mothers: reproductive expenditure and resource availability in bighorn ewes

We present a marginal value model explaining intraspecific andinterspecific variation of mating systems in nonterritorialungulates. The model takes into account the simultaneous effectsof spatial and temporal distribution of females, female groupsize, male-male competition, female choice, and the operationalsex ratio (i.e., the proportion of estrous females). The modelpredicts that higher numbers of females per group increasesthe average exploitation time of such groups by males. An increasein female group density, operational sex ratio, and age-specificfighting success of males are predicted to reduce the averageexploitation time of female groups, leading to roving of males(i.e., moving between female groups). In contrast, an increasein die female rejection rate of males and in the time spentby males on nonmating activities (i. e., foraging, lying down,ruminating, migrating) are predicted to increase the averageexploitation time of female groups and to favor staying behaviorof males (i.e., defending a female group over a longer periodof time). Consequently, die model predicts that young maleswill tend to be "stayers," whereas middle-aged and old malesare expected to be "rovers." Model predictions were tested widifield data collected on muskoxen Ovibos moschatus in a naturalpopulation in west Greenland. Observed correlations betweenbull exploitation times of cow groups and the six above-mentionedsocial and environmental parameters were all in die predicteddirection and statistically significant in five of die six cases.Overall, 69% of die observed variation in exploitation timeof cow groups by males was explained by die model predictions.Stepwise regression suggested that, of die six parameters, variationin sex ratio (R² = .56) and time spent on nonmating activities(R² = .35) had the largest effects on male exploitation time.Also, die observed age-specific variation in bull exploitationtime of cow groups was as predicted.     

The minimization of muscular energy expenditure during inspiration in linear models of the respiratory system

The consequences of requiring a general linear model of respiratory mechanics to inspire a fixed volume in a fixed time in a way that minimizes various measures of muscular energy expenditure are examined. For such a model no volume profile minimizes the time-integral of the applied pressure developed by the respiratory muscles, although this integral is not independent of the profile. Minimizing the mechanical work done by the respiratory muscles, on the other hand, requires that the inspiratory flow be constant. These results support the hypothesis that neither the pressure integral nor the mechanical work are individually minimized over an inspiration by an animal or man at rest. Minimization of a weighted sum of the pressure integral and the work done may be a more physiologically reasonable criterion by which the respiratory muscles direct inspiration. This combined cost function predicts a non-constant optimum velocity profile.     

Length of gestation in ewes carrying lambs of two different breeds

Length of gestation was studied in pregnancies established by intrabreed, interbreed, and mixed-breed embryo transfers of Finnish Landrace (Finn; mean gestation: 144.9 days) and Targhee (mean gestation: 150.4 days) embryos to Finn cross and Targhee recipients. At least one lamb of each breed comprised mixed-breed pregnancies. There was a significant effect of the breed of lamb (Finn, Targhee, or Finn and Targhee) on the length of gestation (P < .01), but not of breed of recipient. Mixed-breed pregnancies had a mean gestation period intermediate between those for pregnancies which contained only one breed of lamb. The mean gestation period for mixed-breed pregnancies was 2.10 +/- .70 (x +/- S.E. ) days longer than for pregnancies with only Finn lambs (P < .01) and 2.99 +/- .73 days shorter than for pregnancies with only Targhee lambs (P < .001). The delay in parturition in mixed-breed pregnancies beyond the normal gestation period for Finn lambs occurred even in litters with a majority of Finn lambs. These results demonstrate an interaction between fetuses in the processes leading to parturition. Possible mechanisms by which the Targhee lamb delayed parturition in mixed-breed pregnancies are discussed.     

Measuring energy expenditure in birds using bolus injections of 13C-labelled Na-bicarbonate

The ¹³C-labelled Na-bicarbonate technique uses stable isotopes to measure energy expenditure in birds. After administration, the isotopes reach equilibrium within the body's bicarbonate pools at a fast rate due to the small size of the bicarbonate pool in relation to CO₂ flux. This technique is therefore ideal for measuring energy expenditure over short-term activities. The major advantage of this technique is that it can be applied without the animal having to wear a respirometry mask or being enclosed in a respirometry chamber. Despite the technique's suitability for use in birds and other animals, there have been few studies that have used it to date and so its potential is not fully understood. Here we discuss the methodology and review previous applications.     

Estimation of energy expenditure during walking and jogging by using an electro-pedometer

Using an electro-pedometer which is commercially available, energy expenditure during walking and/or jogging was assessed, and was compared with that obtained by oxygen uptake (VO2). Thirteen male students and 12 female students exercised on 6 minutes duration treadmill tests which velocities were 40, 60, 80, 100, and 120m/min for walking and 100, 120, 140, 160, and 180m/min for jogging, respectively. During exercise, energy expenditure was calculated by VO2 value and respiratory exchange ratio, and was estimated by an electro-pedometer. There was a significant linear relationship between energy expenditures estimated by the pedometer and calculated by VO2 during walking and jogging. To predict energy expenditure more precisely by the electro-pedometer, it is suggested that more precise value of stride should be inputted into the pedometer. In conclusion, the present study showed that commercially available electro-pedometer is able to use for the estimation of energy expenditure with precise validity during walking and/or jogging.     

Nectar intake and energy expenditure in a flower visiting bat

Summary In a coastal region of Venezuela the daily energy expenditure (DEE) and water turnover of the flower visiting bat Anoura caudifer was measured by using the doubly labeled water method. In flower visitors, this method allows independent measurement of energy intake and expenditure if the animals drink no additional water and if the nectar's energy content is known. An average DEE of 12.4 kcal/d and water exchange of 13.4 ml/d were found. Our data show a balanced energy budget when animals in the field imbibe nectar with a sugar concentration of 18–21%, which is roughly medial in the range of nectar concentrations of various bat flowers. The energy turnover of flower visiting bats is high compared with DEEs of other bat species, small mammals and birds; flower visiting bats seem to belong to those species having a fast spin of the life motor.