Body composition analysis of pigs by dual-energy x-ray absorptiometry

Thermoregulation mechanisms and perspectives for validating thermal windows in pigs with hypothermia and hyperthermia: An overview

Specific anatomical characteristics make the porcine species especially sensitive to extreme temperature changes, predisposing them to pathologies and even death due to thermal stress. Interest in improving animal welfare and porcine productivity has led to the development of various lines of research that seek to understand the effect of certain environmental conditions on productivity and the impact of implementing strategies designed to mitigate adverse effects. The non-invasive infrared thermography technique is one of the tools most widely used to carry out these studies, based on detecting changes in microcirculation. However, evaluations using this tool require reliable thermal windows; this can be challenging because several factors can affect the sensitivity and specificity of the regions selected. This review discusses the thermal windows used with domestic pigs and the association of thermal changes in these regions with the thermoregulatory capacity of piglets and hogs.

Phenotyping of the Visceral Adipose Tissue Using Dual Energy X-Ray Absorptiometry (DXA) and Magnetic Resonance Imaging (MRI) in Pigs

The objective of this study was to phenotype visceral adipose tissue (VAT) in pigs. In this context, the ability to detect VAT by using the DXA CoreScan mode within the enCORE software, version 17 (GE Healthcare) was evaluated in comparison with MRI measurements (Siemens Magnetom C!) of the same body region. A number of 120 crossbred pigs of the F1 and F2 generation, with the parental breeds Large White, Landrace, Piétrain, and Duroc, were examined at an age of 150 days. A whole-body scan in two different modes ("thick", "standard") was carried out by a GE Lunar iDXA scanner. Very strong relationships (R² = 0.95, RMSE = 175cm³) were found for VAT between the two DXA modes. The comparison of VAT measured by MRI and DXA shows high linear relationships ("thick": R² = 0.76, RMSE = 399.25cm³/"standard": R² = 0.71, RMSE = 443.42cm³), but is biased, according to the Bland-Altman analysis. A variance analysis of VAT shows significant differences for both DXA modes and for MRI between male and female pigs, as well as between F1 and F2. In conclusion, DXA "CoreScan" has the ability to estimate VAT in pigs with a close relationship to MRI but needs bias correction.

"Sex" and body region effects on bone mineralization in male pigs

Lameness in pigs is one of the major reasons for culling and early losses in pigs. This can be linked to osteoporosis due to pathologic alterations in bone mineral density (BMD) or bone mineral content (BMC) and may also be linked to the sex. Dealing with the ban on piglet castration without anaesthesia in Germany 2021, we have three male “sex” types: entire boars (EB), immunocastrated boars (IB), and surgically castrated boars (SB). The hypothesis of the present study is that BMC or BMD varies between different male sex types. If sex has an effect on bone mineralization (BMC or BMD) and if this affects leg health, it could result in more lameness and problems during fattening in the negatively affected sex type. The present study evaluated bone mineralization (in terms of BMD and BMC) and body composition traits using dual-energy X-ray absorptiometry (DXA) three times during growth at 30, 50, and 90 kg live body weight. Nine body regions were analysed for bone mineral traits and compared for different male sex types and the fattening season. Significant differences were found regarding BMD (and BMC) among EB, IB, and SB for whole-body BMD (BMC). Additionally significant differences were found in the front and lower hind limbs, where SB showed a significantly higher BMD compared to EB, with IB in between. Additionally regional differences were detected among the groups. Further studies are needed to evaluate the effect of these differences in bone mineralization on leg health.

Dietary Calcium to Digestible Phosphorus Ratio for Optimal Growth Performance and Bone Mineralization in Growing and Finishing Pigs

Simple Summary

Minimizing the use of dietary non-renewable mineral phosphates improves the sustainability of phosphorus use in growing-finishing pigs. As the phosphorus metabolism is closely linked to calcium, this experiment compared three dietary calcium to digestible phosphorus ratios within two phosphorus levels to determine the optimum levels for growth performance and bone mineralization. The lowest calcium level was insufficient for an efficient metabolic use of P, the medium level was sufficient to maximize growth performance and highest level further improved bone mineralization. The low digestible phosphorus level enabled a complete removal of supplemented mineral phosphates in the finisher period, which resulted, per pig, in a decrease of its use by 65% and a decrease of the calculated P excretion by 41%, without impaired growth performance. However, a reduced bone mineralization was observed. This study shows that there is potential to reduce the digestible phosphorus compared to practiced levels in grower–finisher pigs and shows that the optimal calcium to digestible phosphorus ratio needs to be maintained at the upper range of the actually available recommendations.

Abstract

Within the context of maximizing the use of dietary phosphorus, a growing-finishing pig study was conducted to determine the optimal total dietary calcium (Ca) to digestible phosphorus (dP) ratio and to verify the possibility of mineral phosphate removal during the finishing period on growth performance and mineral status. The potential for replacing chemical and mechanical bone properties by dual energy X-ray absorptiometry (DXA) measures on non-dissected feet was also verified. Three Ca to dP ratios (2.2:1, 2.5:1 and 2.8:1) within two dP levels (P+, P–) were fed during 91 days to 84 pigs. The grower and finisher P+ diets contained 3.0 and 2.4 and P– diets contained 2.5 and 1.7 g dP/kg, respectively. Growth performance and blood serum mineral content were independent of treatments, except that 2.2:1 impaired finisher feed conversion ratio compared to 2.5:1 and 2.8:1. Urinary P concentration increased by 37% in 2.2:1 compared to 2.5:1 and 2.8:1. Maximal load on bone and DXA mineral density were reduced in 2.2:1 compared to 2.8:1. Bone ash and volumetric density were reduced in 2.2:1 and 2.5:1 compared to 2.8:1. Diet P– reduced bone ash, maximal load, volumetric density and DXA bone mineral content and density. No interaction was observed between Ca and dP level. Therefore, 2.2:1 was insufficient for an efficient metabolic use of P, 2.5:1 was sufficient to maximize growth performance and 2.8:1 further improved bone mineralization. Increasing dietary Ca did not impair bone zinc content. Diets P– without supplemented mineral phosphates during the finisher period resulted, per pig, in a decrease of its use by 65% and of the calculated P excretion by 41%, without impaired growth performance. Finally, DXA data responded to dietary treatments as did labor intensive chemical and mechanical bone properties.

Dual-energy X-ray absorptiometry scans accurately predict differing body fat content in live sheep

Background

There is considerable interest in implementing mobile scanning technology for on-farm body composition analysis on live animals. These experiments evaluated the use of dual energy X-ray absorptiometry (DXA) as an accurate method of total body fat measurement in live sheep.

Results

In Exp. 1, visceral and whole body fat analysis was undertaken in sheep with body condition scores (BCS) in the range 2 to 3.25 (scale 1: thin to 5: fat). The relationship of BCS was moderately correlated with visceral fat depot mass (r = 0.59, P < 0.01, n = 24) and whole body fat (r = 0.70, P < 0.001, n = 24). In Exp. 2, sheep with BCS in the range 2.25 to 3.75 were blood sampled to analyse circulating leptin concentrations, and were DXA scanned immediately post mortem for total body fat. Plasma leptin concentrations had low correlations with BCS (r = 0.50, P < 0.05, n = 17) and DXA body fat (r = 0.42, P < 0.05, n = 17), and no correlation with chemical body fat (r = 0.17, P > 0.05, n = 9). There was a moderate correlation between DXA body fat and BCS (r = 0.70, P < 0.01, n = 17), and DXA body fat was highly correlated with chemical body fat (r = 0.81, P < 0.001, n = 9). In Exp. 3, a series of five DXA scans, at 8-week intervals, was performed on growing sheep over a 32-week period. The average BCS ranged from 2.39 ± 0.07 (S.E.M.) to 3.05 ± 0.11 and the DXA body fat (%) ranged from 16.8 ± 0.8 to 24.2 ± 1.2. There was a moderate correlation between DXA body fat and BCS over the 32 weeks (r = 0.61, P < 0.001, n = 24).

Conclusions

Overall, these experiments indicated that there was good agreement between BCS, DXA and chemical analysis for measuring total body fat in sheep, and that DXA scanning is a valid method for longitudinal measurement of total body fat in live sheep.

Accuracy of predicting chemical body composition of gilts and sows

Physical and chemical body composition of gilts and parity 3 sows were used to determine current prediction equation accuracy and propose alternative prediction equations that incorporate additional variables. Longissimus dorsi muscle depth and parity can be combined with body weight and backfat to improve gilt and sow body composition prediction.

Electropharmacological characterization of microminipigs as a laboratory animal using anti-influenza virus drug oseltamivir

We analyzed electropharmacological characteristics of microminipigs under halothane-anesthesia using anti-influenza virus drug oseltamivir, which has been known to possess multi-channel blocking properties, including Na⁺, Ca²⁺ and K⁺ channels (n = 4). Oseltamivir in doses of 0.3, 3 and 30 mg/kg was intravenously infused over 10 min with an interval of 20 min, which provided peak plasma concentrations 1.4, 7.4 and 125.5 µg/mL, respectively. The low dose did not alter any of the cardiovascular variables. The middle dose decreased the heart rate at 30 min after the start of the infusion. The high dose transiently returned the heart rate toward the baseline for 10-15 min, but decreased it for 20-60 min; decreased the mean blood pressure for 5-60 min; prolonged the PR interval for 10-60 min, and the QRS width for 10-20 min; but shortened the QT interval for 10-30 min, and the QTc for 5-60 min. Thus, oseltamivir can suppress the sinus automaticity, and atrioventricular nodal and intraventricular conduction; and decrease the mean blood pressure, extents of which were greater in microminipigs than in beagle dogs in our previous observation in spite of similar plasma concentrations, reflecting higher sensitivity of microminipigs for Na⁺ and Ca²⁺ channel inhibition than that of beagle dogs. In contrast to beagle dogs, oseltamivir shortened the repolarization period in microminipigs, indicating that oseltamivir can more potently inhibit the inward currents than the outward ones in the hearts of microminipigs. This information may help improve utilizatione of microminipigs as a laboratory animal.

Characterization of microminipigs as an in vivo experimental model for cardiac safety pharmacology

We pharmacologically characterized microminipigs as an in vivo experimental model by assessing cardiovascular effects of pilsicainide, verapamil and E-4031, which can preferentially inhibit cardiac Na⁺, Ca²⁺ and K⁺ channels, respectively. Intravenous infusion of 1 mg/kg of pilsicainide (n = 4), 0.1 mg/kg of verapamil (n = 4) and 0.01 followed by 0.1 mg/kg of E-4031 (n = 5) over 10 min decreased the heart rate, mean blood pressure and ventricular contractility. Moreover, pilsicainide prolonged the PR interval, QRS width and QTc; verapamil prolonged the PR interval, but shortened the QRS width and QTc; and E-4031 prolonged the QTc, whereas no substantial change was detected in the PR interval or QRS width. Peak plasma concentrations of pilsicainide, verapamil and E-4031 in microminipigs were 1.7-4.8 times higher than those expected in humans and dogs, possibly due to smaller effective volume of drug distribution. The extent of the drug-induced cardiovascular responses was generally greater in microminipigs than in humans and dogs, which could be explained by the following possibilities; namely unique pharmacokinetic profile, less great reflex-mediated increase of sympathetic tone and/or smaller repolarization reserve in microminipigs. These information may make it feasible to apply this new-type animal to a tool for assessing cardiac safety profiles of new chemical entities.

Empty body chemical composition estimated from non-carcass parts in Belgian Blue double-muscled bulls

Properties of the non-carcass parts in combination with empty body and half carcass weight (EBW and CCW; kg) were used to generate equations for predicting empty body chemical composition. Therefore, chemical composition of the non-carcass parts and weight of the depot fatty tissues were determined on 18 Belgian Blue double-muscled fattening bulls. Very high coefficients of determination (R2) were found between the empty body composition and on the one hand the non-carcass parts composition and on the other hand the weight of the fatty tissues. Fat in the empty body was most difficult to predict. The very high coefficients of determination are partly caused by the large variation in slaughter weight (309 to 723 kg). Therefore equations to estimate proportional composition of the empty body are discussed. Although R2 values are strongly reduced, residual standard deviations remain very low and the precision of prediction is good. The proportion of protein is most difficult to predict, as it shows a very small variation. Estimations based on composition of the non-carcass parts are mostly a little more precise than the estimates based on weight of the fatty tissues but as the latter are much easier to determine, these equations will be more appropriate for practical use. Similarly the little improvement of the estimation based on EBW instead of CCW, cannot account for the extra costs and time to determine EBW. The results of the homogenizations have proven that there is very little variation in composition, despite the large range in slaughter weight. As the Belgian Blue double-muscled animals are very deviant from other breeds, the equations found in this study can only be applied for this breed type.

Bone mineralisation of weaned piglets fed a diet free of inorganic phosphorus and supplemented with phytase, as assessed by dual-energy X-ray absorptiometry

Sixteen female piglets (58 d of age, 16.8 ± 0.8 kg body weight [BW]) were assigned to two groups (n = 8) and received until day 100 of age (50.3 ± 1.2 kg BW) ad libitum either a diet with a standard (diet C) or low (diet L) total phosphorus (P) content (5.38 and 4.23 g/kg, respectively). Diet C was supplemented with mineral P (1.15 g/kg) and did not contain microbial phytase. Diet L did not contain any inorganic P but 750 FTU/kg of microbial phytase. Despite these treatments, both diets were composed with the same ingredients. Body mineralisation of each gilt was assessed by determining the bone mineral content (BMC), area bone mineral density (BMD) by the dual-energy X-ray absorptiometry (DXA) at days 58, 72, 86 and 100 of age. Feeding diet L caused a higher P digestibility (p = 0.008) measured from days 72 to 86 of age and at 100 days of age a higher BMC and BMD (p ≤ 0.01). Furthermore, the gilts of group L deposited more minerals in the body than control pigs (by 2.4 g/d, p = 0.008). It was found that BMD and BMC were positively correlated with body lean mass and digestible P intake. The results indicated that, even for very young pigs, the addition of microbial phytase instead of inorganic P increases the amount of digestible P covering the requirements of piglets for proper bone mineralisation. Furthermore, it was proved that the DXA method can be successfully applied to measure body fat and lean mass contents as well as bone mineralisation of growing pigs using the same animals.

Evaluation of carcass composition of intact boars using linear measurements from performance testing, dissection, dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI)

The objective of this study was to investigate non-invasive imaging methods to update the used regression equation for stationary tested boars. A total of 94 boars were examined. 20 boars were dissected to provide the reference LMP. Performance data (PD) from right carcasses were available from all groups. The left carcasses were studied by MRI & DXA. Based on the reference LMP and the MRI & DXA data, regression equations for LMP were developed. The estimates for LMP based on MRI & DXA data were used to calculate new regression equations for entire male carcass halves based on linear PD. Further 33 PD sets served as independent sample, which was included in a Monte Carlo simulation for imputing the missing reference LMPs (n=74) and discussing the accuracy of the results. The LMP regression equation based on the combined MRI & DXA data is as accurate as the former regression equation, but needs only three instead of seven variables.

Effect of body mass and clothing on carrion entomofauna

Carcass mass largely affects pattern and rate of carrion decomposition. Supposedly, it is similarly important for carrion entomofauna; however, most of its likely effects have not been tested experimentally. Here, simultaneous effects of carcass mass and clothing are analyzed. A factorial block experiment with four levels of carcass mass (small carcasses 5–15 kg, medium carcasses 15.1–30 kg, medium/large carcasses 35–50 kg, large carcasses 55–70 kg) and two levels of carcass clothing (clothed and unclothed) was made in a grassland habitat of Western Poland. Pig carcasses (N = 24) were grouped into spring, early summer, and late summer blocks. Insects were sampled manually and with pitfall traps. Results demonstrate that insect assemblages are more complex, abundant, and long-lasting on larger carcasses, whereas clothing is of minor importance in this respect. Only large or medium/large carcasses were colonized by all guilds of carrion insects, while small or medium carcasses revealed high underrepresentation of late-colonizing insects (e.g., Cleridae or Nitidulidae). This finding indicates that carcasses weighing about 23 kg—a standard in forensic decomposition studies—give an incomplete picture of carrion entomofauna. Residencies of all forensically relevant insects were distinctly prolonged on larger carcasses, indicating that cadaver mass is a factor of great importance in this respect. The pre-appearance interval of most taxa was found to be unrelated to mass or clothing of a carcass. Moreover, current results suggest that rate of larval development is higher on smaller carcasses. In conclusion, this study demonstrates that carcass mass is a factor of crucial importance for carrion entomofauna, whereas the importance of clothing is small.

Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers

Aalhus, J. L., López-Campos, Ó., Prieto, N., Rodas-González, A., Dugan, M. E. R., Uttaro, B. and Juárez, M. 2014. Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers. Can. J. Anim. Sci. 94: 545–556. Beef value is in the eye, mouth or mind of the consumer; however, currently, producers are paid on the basis of carcass grade. In general, affluent consumers are becoming more discerning and are willing to pay for both credence and measureable quality differences. The Canadian grading system for youthful carcasses identifies both lean yield and quality attributes, whereas mature carcasses are broadly categorized. Opportunities exist to improve the prediction of lean meat yield and better identify meat quality characteristics in youthful beef, and to obtain additional value from mature carcasses through muscle profiling. Individual carcass identification along with development of database systems like the Beef InfoXchange System (BIXS) will allow a paradigm shift for the industry as traits of economic value can be easily identified to improve marketing value chains. In the near future, developing technologies (e.g., grade cameras, dual energy X-ray absorptiometry, and spectroscopic methods such as near infrared spectroscopy, Raman spectroscopy and hyperspectral imaging) will be successfully implemented on-line to identify a multitude of carcass and quality traits of growing importance to segments of the consuming population.

In vivo body composition in autochthonous and conventional pig breeding groups by dual-energy X-ray absorptiometry and magnetic resonance imaging under special consideration of Cerdo Ibérico

The improvement of carcass quality is one of the main breeding goals in pig production. To select appropriate breeding animals, it is of major concern to exactly and reliably analyze the body composition in vivo. Therefore, the objective of the study was to examine whether the combination of dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) offers the opportunity to reliably analyze quantitative and qualitative body composition characteristics of different pig breeding groups in vivo. In this study, a total of 77 pigs were studied by DXA and MRI at an average age of 154 days. The pigs originated from different autochthonous or conventional breeds or crossbreeds and were grouped into six breed types: Cerdo Ibérico (Ib); Duroc × Ib (Du_Ib); White Sow Lines (WSL, including German Landrace and German Large White); Hampshire/Pietrain (Pi_Ha, including Hampshire, Pietrain × Hampshire (PiHa) and Pietrain × PiHa); Pietrain/Duroc (Pi_Du, including Pietrain × Duroc (PiDu) and Pietrain × PiDu); crossbred WSL (PiDu_WSL, including Pietrain × WSL and PiDu × WSL). A whole-body scan was performed by DXA with a GE Lunar DPX-IQ in order to measure the amount and percentage of fat tissue (FM; %FM), lean tissue (LM; %LM) and bone mineral, whereas a Siemens Magnetom Open with a large body coil was used for MRI in the thorax region between 13th and 14th vertebrae in order to measure the area of the loin (LA) and the above back fat area (FA) of both body sides. A GLM procedure using SAS 9.2 was used to analyze the data. As expected, the native breed Ib followed by Du_Ib crossbreeds showed the highest %FM (27.2%, 25.0%) combined with the smallest LA (46.2 cm2, 73.6 cm2), whereas Ib had the lowest BW at an average age of 154 days. Pigs with Pi_Ha origin presented the least %FM (12.4%) and largest LA (99.5 cm2). The WSL and PiDu_WSL showed an intermediate body composition. Therefore, it could be concluded that DXA and MRI and especially their combination are very suitable methods to reliably identify differences in body composition and carcass traits among different pig lines in vivo.

Comparison of various methods for estimating body fat in dogs

Obesity is considered one of the most common forms of malnutrition occurring in dogs. Laboratory methods of evaluation of body composition in live dogs have included dual-energy X-ray absorptiometry (DEXA) and deuterium oxide (D(2)O) dilution. Clinical methods of evaluation include assigning a body condition score (BCS) based on visual observation, palpation, and morphometric measurements. This study used these four methods to evaluate 23 healthy, adult, client-owned dogs. Good correlation (coefficient of determination [r(2)]=0.78) was found between measurements of percent body fat (%BF) determined by the D(2)O dilution method and the DEXA scan. Percent body fat can also be estimated using BCS (r(2)=0.92 comparison with DEXA) or by using morphometric measurements with simple calculations (r(2)=0.92 comparison with DEXA).

Estimation of whole body lipid mass in finishing pigs

Most nutritional pig growth models are based on the deposition of whole body protein (P) and lipid (L) mass. Chemical analysis of the whole animal is the best method to determine body composition. However, this method is expensive, time consuming and the carcass is lost. Alternatively, P and L may be estimated using simple indicators that should be precise and easily accessible. Although empty body weight (EBW) is a good indicator for P (through the strong relation between water and P), L is more difficult to estimate. This study was carried out to evaluate the relationship between simple carcass measurements and L. Measurements included backfat thicknessin vivoand at slaughter in the hot and cold carcass and the weight of carcass, organs and primal cuts. To maximize variations in adiposity a total of 30 females and barrows from two genotypes (Piétrain×(Landrace×Large White) and Large White) were slaughtered at body weights typically used in Europe (i.e. 90 to 150 kg) and ground for chemical analysis. Backfat mass (in combination with EBW) was the best indicator for L (L (kg)=0·0590×EBW (kg)+2·99×backfat mass (kg),R2=0·96). Different backfat thickness measurements were highly correlated and appeared reasonable indicators for total backfat mass. Backfat thickness measured in the hot carcass between 3rd and 4th last lumbar vertebra at 8 cm from the mid line was the second best indicator for L (L=(0·0855+0·0073×backfat thickness)×EBW,R2=0·94). On average, 18% of total body lipids were located in the backfat. Although these equations can be used to obtain a reasonable estimate of whole body lipid mass, a significant genotype effect remained. Differences between genotypes in the partitioning of lipids between different tissues suggest that the quantification of an external lipid depot alone is insufficient to precisely estimate whole-body lipid mass across genotypes.

The use of dual-energy X-ray absorptiometry to estimate the dissected composition of lamb carcasses

A total of 140 male and female Dorset and Suffolk lambs were slaughtered according to four live weight classes (36-39kg, 41-44kg, 46-49kg and 51-54kg). Total tissue, fat and lean masses, and bone mineral content measured by dual-energy X-ray absorptiometry (DXA) were used to predict dissected tissue weights. The DXA total weights accurately predict half-carcasses and primal cuts weights (shoulder, leg, loin and flank) (R(2)>0.99, CVe<1.3%). The prediction of the half-carcass dissected fat percentage is weaker (R(2)=0.77, CVe=10.4%). Fatness prediction accuracy is equivalent for the shoulder, leg and loin (R(2) between 0.68 and 0.78, CVe between 10% and 13%). The R(2) obtained when predicting dissected lean content from DXA variables is 0.93 for the half-carcass and higher than 0.83 for all cuts other than flank (CVe are between 3.5% and 6.5%, except for the flank, which is 9.1%). The prediction of bone weight using the bone mineral content is not very accurate for the half-carcass, shoulder and leg (R(2): 0.48, 0.47 and 0.43; CVe: 10.2%, 12.0% and 11.6%, respectively). The situation improves, however, for the loin (R(2)=0.70, CVe=10.7%). In conclusion, DXA is an effective technology for predicting total weight and the amount of lean and fat in lamb carcasses and their primal cuts.

Repeatability of pig body composition measurements using dual energy X-ray absorptiometry and influence of animal size and subregional analyses

Fifteen Large White × Landrace male pigs were used to investigate the influence of animal size and subregional analysis technique on dual energy X-ray absorptiometry body composition measurements and their repeatability. Pigs were scanned in triplicate with an Hologic QDR4500A X-ray absorptiometer at the beginning of the study (3 weeks of age, liveweight 5–10 kg) and then every 4 weeks until 19 weeks of age. Measurements made by dual energy X-ray absorptiometry included total tissue mass, lean tissue mass, fat tissue mass and bone mineral content. The QDR4500 software allows the scanned image to be divided into head, arms, legs and trunk using an in-built regional analysis grid that contains algorithms unique to each region. Different regional grid manipulations were performed at each scan to evaluate the effects of incorporating subregions into a whole body analysis over time. The dual energy X-ray absorptiometry measurements were highly repeatable and measurement repeatability improved as animal size increased. When results were averaged across regional grid placement and scan time, the most repeatable measurement was total tissue mass (CV = 0.21%), followed by lean tissue mass (CV = 0.59%), bone mineral content (CV = 2.50%) and fat tissue mass (CV = 2.71%). The placement of the regional analysis grid influenced the repeatability of all measurements except for total weight; however, this influence reduced with increasing animal size. It is recommended that the body of the scan image be positioned in the arm region and the head in the head region of the software regional analysis grid to measure whole body composition in pigs because it provides the most repeatable measure overall. Animal placement into the trunk region or utilising the full regional analysis option as specified by the manufacturer provided less repeatable results.

Assessment of nutritional status in rhesus monkeys: comparison of dual-energy X-ray absorptiometry and stable isotope dilution

Body composition estimates from dual-energy X-ray absorptiometry and stable isotope dilution ((2)H and (18)O) were compared in 61 rhesus monkeys (Macaca mulatta) from the ongoing long-term energy restriction study at the University of Wisconsin. Their average age was 18.9 +/- 2.5 y/o. Of the animals, 51% were in the energy restricted group and 38% were females. Although the correlation between methods was highly significant for fat mass (R(2) = 0.97, SEE = 0.25 kg or 7.5%, P < 0.0001) and fat-free mass (R(2) = 0.98, SEE = 0.29 kg or 3.6%, P < 0.0001), we observed that dual-energy X-ray absorptiometry underestimated fat mass by 0.67 +/- 0.26 kg (7.5%, P < 0.0001) and overestimated fat-free mass by 0.57 +/- 0.29 kg (20%, P < 0.0001) when compared with isotope dilution. Taken together with data from the literature, the present results emphasize the usefulness of dual-energy X-ray absorptiometry to derive body composition and thus nutritional status in monkeys, but demonstrate the importance of validation experiments for a given DXA model and software.

The accuracy of dual energy X-ray absorptiometry (DXA), weight, and P2 back fat to predict half-carcass and primal-cut composition in pigs within and across research experiments

A Hologic QDR4500A dual energy X-ray absorptiometer (DXA) was used to measure body composition in 199 half-carcasses ranging from 15 to 48 kg. Half-carcasses were from animals of mixed sex and of either Large White × Landrace or Large White × Landrace × Duroc descent. Half-carcasses were selected from 5 different experiments to evaluate DXA accuracy within and across experiments. Values determined by DXA including total tissue mass, fat tissue mass, lean tissue mass, and bone mineral content, for the half-carcass and the shoulder, loin, belly, and ham primal cuts were evaluated by comparison with manually dissected composition. Relationships between manually dissected values and measurements of weight and backfat at the P2 site were also evaluated. Manually dissected values were strongly related to DXA-derived values, more so than with weight and P2 or a combination of both, particularly in the measurement of fat composition. In contrast to estimates derived from weight and P2, DXA-derived estimates remained accurate even when between-experiment variation was included. However, because DXA estimates were different from manually dissected values, they would need to be adjusted with the use of appropriate regression equations to correct the in-built algorithms. These results demonstrate the efficacy of DXA as a non-destructive method for determining the composition of the half-carcass and primal cuts, and its greater precision than current routinely used methods.

Exogenous porcine somatotropin administered to neonatal pigs at high doses can alter lifetime fat but not lean tissue deposition

The growth rate of the young pig is generally much less than its potential and may be constrained by endocrine status as well as nutrient intake. The aim of the present study was to determine whether porcine (p) somatotropin (ST) treatment of the sucking pig could alter subsequent body composition. Twelve mixed-parity cross-bred sows with an average litter size of ten piglets were used to nurse pigs for the present study. On day 1 of lactation, the median two male pigs (by weight) from each litter were randomly allocated to one of two doses of pST (0 or 1 mg/kg per d) until weaning on day 21. Pigs were weaned and offered feed ad libitum until slaughter at 134 d of age. Body composition was measured using dual-energy X-ray absorptiometry (DXA) at 21, 49, 77, 105 and 133 d of age. There was no significant difference in growth rates between day 1 and 21 of lactation in pigs injected with either saline (9 g/l NaCl/l) or pST (258 v. 246 g/d for control and pST-treated pigs respectively, P=0.61), and as a consequence there was no significant difference in liveweight at weaning (7.13 v. 6.84 kg, P=0.59). However, fat mass at weaning tended to be decreased (1.18 v. 0.96 kg, P=0.064), while the % fat in the body at weaning was significantly (16.7 v. 13.9 %, P=0.008) decreased by exogenous pST treatment. In the immediate post-weaning period there was a reduction in lean tissue deposition (347 v. 300 g/d, P=0.021) but no effect on fat deposition (35 v. 33 g/d, P=0.72). Over the entire weaning-to-slaughter period, pST treatment of neonatal pigs decreased the rate of fat deposition (130 v. 112 g/d, P=0.033), but had no effect on lean tissue deposition (550 v. 538 g/d, P=0.49). Therefore, treatment of nursing pigs with high doses of pST for a short period before weaning may provide a means of reducing the fat content of pork and pork products.

Evaluation of a new pediatric air-displacement plethysmograph for body-composition assessment by means of chemical analysis of bovine tissue phantoms

BACKGROUND

Body-composition assessment reflects infant growth and nutritional status but is limited by practical considerations, accuracy, and safety.

OBJECTIVE

This study evaluated the precision and accuracy of a new air-displacement plethysmography (ADP) system for pediatric body-composition assessment.

DESIGN

We used 24 phantoms constructed from bovine lean muscle and fat. The phantoms varied in mass (1.3894-9.9516 kg) and percentage fat (%Fat; 2.08-34.40%), thereby representing infants between birth and 6 mo of age. Estimates of %Fat obtained with chemical analysis (CA), hydrostatic weighing, and ADP were compared.

RESULTS

There was no significant difference between %Fat measured with ADP (%Fat(ADP)) and %Fat measured with CA (%Fat(CA)); the mean values were 18.55% and 18.59%, respectively. SDs for %Fat(ADP) and %Fat(CA) were not significantly different (0.70% and 0.73%, respectively). %Fat measurements obtained with ADP, CA, and hydrostatic weighing were highly correlated (r > 0.99, P < 0.0001). The regression equation (%Fat(CA) = 0.996%Fat(ADP) + 0.119; SEE = 0.600; adjusted R(2) = 0.997; P < 0.0001) did not differ significantly from the line of identity (%Fat(CA) = %Fat(ADP)). There was high agreement between individual measurements of %Fat(ADP) and %Fat(CA), as shown by the narrow 95% limits of agreements between methods (-1.22% to 1.13%), and there was no systematic bias in individual differences across the phantom mass and %Fat ranges.

CONCLUSION

ADP provides a highly precise and accurate estimate of %Fat in bovine tissue phantoms in the pediatric ranges of body weight and body fatness.

Validation of dual energy X-ray absorptiometry (DXA) by comparison with chemical analysis of dogs and cats

BACKGROUND

Dual-energy X-ray absorptiometry (DXA) has been used extensively to measure body composition, but has been validated by comparison to chemical analysis on relatively few occasions. Moreover, these previous validation studies have ground up entire carcasses prior to chemical analysis, thus potentially obscuring sources of error in the DXA analysis.

OBJECTIVE

The purpose of this study was to validate DXA by comparison to chemical analysis in dogs and cats, performing chemical analysis on dissected rather than ground carcasses to reveal sources of discrepancy between the two methods.

DESIGN

Sixteen animals (10 cats and 6 dogs weighing between 1.8 and 22.1 kg) were scanned by DXA post-mortem using a Hologic QDR-1000 W pencil beam machine and then dissected into 22 separate components. Individual tissues were dried and then sub-sampled for analysis of fat content by Soxholet extraction, or ashing in a muffle furnace. Body composition by DXA was compared to body composition by chemical analysis and discrepancies between the two correlated with chemical composition of individual tissues. We also explored the capability of the machine to establish the fat contents of mixtures of ground beef, lard and water.

RESULTS

DXA estimates were strongly correlated with estimates derived from chemical analysis: total body mass (r=1.00), lean tissue mass (r=0.999), body water content (r=0.992) and fat mass (r=0.982). Across individuals the absolute and percentage discrepancies were also small: total body mass (13.2 g, 1.02%), lean tissue mass (119.4 g, 2.64%), water content (101 g, 1.57%) and fat content (28.5 g, 2.04%), where the percentage error is expressed relative to the average mass of that component across all individuals. Although on average DXA compared very well to chemical analysis, individual errors were much greater. Individual errors in the lean tissue and fat tissue components were strongly correlated with the fat content of skeletal muscle and the lean content of mesenteric fat. The error in the DXA estimate of total fat content was related to skeletal muscle hydration. Experimental studies using mixtures of lean ground beef, water and lard indicated that tissue hydration may have important effects on the perception of tissue fat content by DXA. Bone mineral content by DXA was approximately 30% lower than whole body ash content but only 7.7% lower than ash content of the bones.

CONCLUSIONS

On average pencil beam DXA analysis using the Hologic QDR-1000 W machine provides an accurate estimate of body composition in subjects weighing between 1.8 and 22.1 kg. Individual discrepancies, however, can be large and appear to be related to lean tissue hydration.

Dual-energy X-ray absorptiometry in small subjects: influence of dual-energy X-ray equipment on assessment of mineralization and body composition in newborn piglets

There is a growing body of literature that describes the use of dual-energy x-ray absorptiometry (DXA) for bone mineral content (BMC) and fat mass (FM) assessment in neonates, but the reproducibility and accuracy of the method are still controversial. Two different software programs have been developed for use on Hologic densitometers: the Pediatric Whole Body (PWB) and the Infant Whole Body (IWB) programs. They differ in scan time, radiation exposure, and in the algorithm used to assess BMC. We evaluated the reproducibility and accuracy of PWB and IWB in newborn piglets. Reproducibility of body mass (BM), FM, and BMC measurements from PWB and IWB were similar. BM agreed well with scale weight with both software programs; IWB was within +/- 0.5% and PWB was within +/- 0.3% of scale weight. FM was highly correlated with carcass fat (PWB: r = 0.962; IWB: r = 0.980). Errors in the DXA estimation of fat were similar with PWB and IWB. With both software programs, BMC was highly correlated with carcass calcium (PWB: r = 0.925, IWB: r = 0.987), but errors in the DXA estimation of calcium were about twice as high with PWB (+/- 16.9%) than with IWB (+/-9.2%). In four piglets, the addition of a layer of porcine lard was associated with an increase in BMC; this effect was more pronounced with PWB (+ 156%) than with IWB (+ 15%). The IWB software provided BMC measurements that were more precise, accurate, and stable in the presence of added fat than the measurements obtained with PWB, indicating that IWB is superior to PWB for in vivo determination of BMC and body composition.

Neonatal body composition: dual-energy X-ray absorptiometry, magnetic resonance imaging, and three-dimensional chemical shift imaging versus chemical analysis in piglets

An animal study to evaluate dual-energy x-ray absorptiometry (DXA) and magnetic resonance (MR) imaging and spectroscopy for measurement of neonatal body composition was performed. Twenty-three piglets with body weights ranging from 848 to 7550 g were used. After measuring total body water, animals were killed and body composition was assessed using DXA and MR (1.5 T; MR imaging, T1-weighted sagittal spin-echo sequence; MR spectroscopy, three-dimensional chemical shift imaging) as well as chemical carcass analysis (standard methods) after homogenization. Body composition by chemical analysis (percent of body weight, mean +/- SD) was as follows: body water, 75.3 +/- 3.9%; total protein, 13.9 +/- 8.8%; and total fat, 6.5 +/- 3.7%. Absolute content of fat and total ash was 7-674 and 35-237 g, respectively. Mean hydration of fat-free mass was 0.804 +/- 0.011 g/kg and decreased with increasing body weight (r2 = 0.419) independent of age. Using DXA, bone mineral content was highly correlated with calcium content (r2 = 0.992), and calcium per bone mineral content was 44.1 +/- 4.2%. DXA fat mass correlated with total fat (r2 = 0.961). Using MR, spectroscopy and chemical analysis were highly correlated with fat-to-water ratio (r2 = 0.984) and absolute fat content (r2 = 0.988). Total fat by MR imaging volumetry showed a lower correlation (r2 = 0.913) and overestimated total fat by a factor of 2.46. Conversion equations for DXA were developed (total fat = 1.31 x fat mass measured by DXA--68.8; calcium = 0.402 x bone mineral content + 1.7), which improved precision and accuracy of DXA measurements. In conclusion, both DXA and MR spectroscopy give accurate and precise estimates of neonatal body composition and may become valuable tools for the noninvasive assessment of neonatal growth and nutritional status.