Estimating Body Condition Research Articles

Short term repeatability of body fat thickness measurement and body condition scoring in sheep as assessed by a relatively small number of assessors

This study evaluated the intra-observer repeatability of the rump fat thickness (RFT) measurements by ultrasound and body condition scoring (BCS) in sheep, and the reproducibility of RFT and BCS determined i) by six investigators, ii) at different sites (left and right, lumbar and sternal) and iii) in unshorn and shorn sheep. Six investigators with different experience in estimating body condition score in sheep determined BCS and RFT repeatedly at the different sites in 65 ewes before and after shearing. Intra-observer repeatability was greater for repeated measurement of RFT left (r=0.83 and r=0.84, in unshorn and shorn sheep) than RFT right (r=0.64 and r=0.77, resp.). A lower repeatability for measuring the sternal fat thickness (SFT) in unshorn sheep (r=0.31) indicates that this method is not feasible to score ewes. The correlation between fat thicknesses determined at different sites (RFT left, RFT right, SFT) and in unshorn and shorn sheep revealed a generally higher reproducibility of RFT measurements left and right (r=0.63–0.76) compared with the reproducibility of RFT and SFT (r=0.37–0.79). Repeatability and reproducibility varied between investigators and in unshorn and shorn sheep. The repeatability for measuring BCS lumbar in unshorn and shorn sheep was greater (κ=0.73 and κ=0.67, resp.) than for determining BCS sternal (κ=0.01 and κ=0.44, resp.) and varied between investigators and in unshorn and shorn ewes. Reproducibility of lumbar and sternal BSC determined by the six investigators was poor to fair in unshorn and poor to moderate in shorn ewes. In summary, measuring RFT or BCS at a sternal site cannot be recommended. Furthermore, taking measurement on shorn seep improved reproducibility. Based on these results, the assessment of RFT or BCS in sheep has the greatest repeatability in the lumbar region. It has to be noted that this study analyzed the repeatability but not the accuracy of the described methods.

Can you estimate body composition in dogs from photographs?

BackgroundA validated method for assessing the visual characteristics of body condition from photographs (vBCS), would be a useful initial screening tool for client-owned dogs.MethodsIn this retrospective study, photographs taken before and after weight loss from 155 overweight and obese dogs attending a weight management referral clinic were used in designing and testing the feasibility of vBCS. Observers with a range of experience examined the photographs, and estimated body condition indirectly (vBCS) using three different methods. In the first method (vBCSmeasured), the ratio of abdominal width to thoracic width (A:T) was measured, and cut-points used to determine body condition; the second method (iBCSsubjective) involved semi-quantitative examination using visual descriptors of BCS; the third (vBCSadjusted) was a combined approach whereby A:T ratio was first determined, and the final score modified if necessary after assessing photographs.ResultsWhen an experienced observer performed vBCS, there were moderate-to-good associations between body fat (measured by dual-energy X-ray absorptiometry) and the three vBCS methods (median Rs: 0.51-0.75; P < 0.001), and also moderate-to-substantial agreement with actual BCS (median kappa 0.51–0.63; P < 0.001). For operators with a range of experience, moderate-to-substantial agreement was generally seen between actual BCS and the scores determined by all three methods (median Kappa 0.55–0.70, P < 0.001), but the strength of agreement varied amongst observers. Age, sex, breed, coat length, and coat colour had no significant effect on vBCS (P > 0.05 for all). Compared with ideal weight and obese dogs, errors in assessing body condition were more common for overweight dogs (e.g. BCS 6–7/9, P < 0.001) by vBCSadjusted (P = 0.008), and vBCSsubjective (P = 0.021), but not by vBCSmeasured (P = 0.150). For vBCSadjusted, body condition was most often overestimated whilst, for vBCSsubjective, body condition was most often under-estimated.ConclusionsAn estimate of body condition can be obtained from an indirect assessment of photographs, but performance varies amongst observers.

A preliminarily study for predicting body weight and milk properties in lactating Holstein cows using a three-dimensional camera system

Since manual body condition scoring has been widely utilized as an indirect and subjective method to estimate energy reserves of dairy cattle, image analysis has been increasingly researched for use on large farms as an objective and effective measuring instrument for the estimation of body condition score (BCS) and body weight (BW). Recent advances in the technological development of the three-dimensional (3D) cameras may provide innovative feed management tools for dairy farms. The objective of the present study was to evaluate the feasibility of a 3D camera systems in measuring the back posture of lactating Holstein dairy cows to predict the BCS, BW, milk yield (MY), milk fat (MF) and milk protein (MP). The BCSs for eight cows were recorded by two trained observers using a 5-point scale, and other variables were obtained using an automatic milking system during the lactation. Back posture measurements of dairy cows were conducted using the ASUS Xtion Pro sensor. Six geodesic line (GL) lengths were computed using the 3D objects of each cow based on the positions of the right and left hook bones (GLhh), right and left thurl bones (GLtt), right and left pin bones (GLpp), hook and thurl bones (GLht), hook and pin bones (GLhp), and coccygeal ligament (GLcl). In the principal component analysis (PCA), GL, GLpp, and GLcl had the greatest contribution to principal component values (PCV) 1, 2, and 3, respectively, and these three PCVs described 0.887 of the cumulative contribution ratio. Good correlations were found between the observed and predicted values of BCS (R2=0.74), BW (0.80), MY (0.62), MF (0.62), and MP (0.53) based on linear regression equations using the GLs as explanatory variables and parity (1, 2, and >3) as a fixed effect. These results demonstrate that the 3D cameras could represent an innovative tool for estimating body condition and milk properties.

In vivo assessment of dog subcutaneous fat depots by real time ultrasonography and image analysis

Systems for estimating body condition score (BCS) are currently used in canine practice to monitor fatness levels. These tools are cheap and easy to use but lack the necessary precision to monitor small changes in body fat, particularly during weight control treatments or in research. The present work aims to study the application of real-time ultrasonography (RTU) together with image analysis in the assessment of subcutaneous fat depots in dogs. Ultrasound images were collected from five anatomical locations (chest, flank, abdomen, thigh and lumbar) from 28 healthy dogs of different breeds and with a body weight (BW) ranging from 5.2 to 33.0 kg. BCS was collected by visual appraisal using a 5-point scale. Subcutaneous fat thickness (SFT) was estimated from RTU images, using the average of three measurements taken in fat deposits located above the muscles represented in each image. Correlations were established between SFT and BW or BCS as well as a classification of BCS-based fatness [overweight (BCS = 4), ideal (BCS = 3) and lean (BCS = 2)]. SFT was found to differ between the five regions considered (P < 0.001). Abdomen and thigh were the areas displaying the widest variation for the different dogs included in the study and also those correlating most with BW, in contrast to the chest, which showed the least variation. Overall, a strong correlation was found between BCS and SFT. The highest correlations were established for the flank, abdomen and lumbar areas. In every anatomical area, a decrease in SFT was observed across all three BCS classes, ranging from 48 to 65 % among overweight and ideal dogs, and from 46 to 83 % among ideal and lean dogs. Preliminary data showed that within this population there was a strong correlation between BCS and SFT estimated from RTU images. It was also observed that RTU measurements for fat thickness differed among the anatomical points surveyed suggesting differences in their sensitivity to a change in BCS. The images displaying the best prediction value for fatness variations were those collected at the lumbar and abdomen areas.

Prevalence of and risk factors for equine obesity in Great Britain based on owner-reported body condition scores.

Few data are available on the prevalence of obesity in the general equine population of Great Britain (GB), and its associated risk factors. To estimate the prevalence of owner-reported obesity in veterinary-registered horses and ponies in GB, and identify factors associated with obesity. A cross-sectional survey of horse/pony owners in GB was undertaken using a postal questionnaire. Thirty veterinary practices randomly selected horse/pony owners to complete a self-administered postal questionnaire. Owners estimated body condition score using a modified Carroll and Huntington method (1-6 scale), and animals were classified as obese if they were scored as either 5 (fat) or 6 (very fat). Factors associated with obesity were assessed using logistic regression analysis. Prevalence of obesity was 31.2% (n = 247/792; 95% confidence interval [CI] 27.9-34.2%). Factors associated with increased odds of obesity were breed (P<0.001), ease of maintaining weight (P<0.001) and primary use (P = 0.002). Compared to Thoroughbreds, draught-type (odds ratio [OR] 7.3; 95% CI 3.1-17.1), cob-type (OR 5.6; 95% CI 2.5-12.5), native (OR 3.2; 95% CI 1.8-5.78) and Welsh breeds (OR 3.5; 95% CI 1.9-6.2) were more likely to be obese. Animals described as 'good doers' were more likely to be obese than those described as readily maintaining normal weight (OR 3.7; 95% CI 2.6-5.3). Compared to competition animals, animals used for pleasure riding (OR 2.5; 95% CI 1.4-4.4) and nonridden animals (OR 2.9; 95% CI 1.5-5.5) were more likely to be obese. Identification of at-risk breeds and other horse- and management-level risk factors for obesity will enable optimal targeting of owner education regarding management strategies to reduce the frequency of equine obesity.

A novel zoometric index for assessing body composition in adult rabbits

Obesity is an emerging problem in domesticated rabbits, and an easy-to-use measure of adipose tissue mass is needed. The current study aimed to develop a zoometric ratio, capable of estimating...

Prevalence and Risk Factors for Owner‐ Reported Obesity in Horses and Ponies in Great Britain

AimsTo estimate prevalence of owner‐reported obesity in British veterinary‐registered horses and ponies, and identify risk factors associated with obesity.MethodsThirty veterinary practices randomly selected horse owners to complete an ethically approved, self‐administered postal questionnaire. Owners estimated body condition score using a modified Carroll and Huntington method (1–6) and animals were classified as obese if they were scored as 5 (fat) or 6 (very fat). Factors associated with obesity were assessed using logistic regression analysis.ResultsOwner‐reported prevalence of obesity was 31.2% (n = 247/792, 95% CI 27.9–34.2). A greater proportion of obese animals (n = 47/225, 20.9%) had a history of laminitis compared with normal/underweight animals (n = 69/511, 13.5%, P = 0.01). Univariable logistic regression analysis identified several management and horse‐level risk factors. Data from 785 horses were included in the final multivariable logistic regression model, and factors associated with an increased risk of obesity were breed (P&lt;0.001), ease of maintaining weight (P&lt;0.001) and primary use (P = 0.002). Compared with Thoroughbreds, draught‐type (odds ratio [OR] 7.3; 95% CI 3.5–17.1), cob‐type (OR 5.8; 95% CI 2.6–12.8), native (OR 3.1; 95% CI 1.7–5.7), and Welsh breeds (OR 3.5; 95% CI 1.9–6.2) were more likely to be obese. Animals described as ‘good doers’ were more likely to be obese compared those described as readily maintaining normal weight (OR 3.7; 95% CI 2.6–5.3). Compared with animals whose primary use was competition, animals predominantly used for pleasure riding were more likely to be obese (OR 2.5; 95% CI 1.4–4.3), and risk increased in non‐ridden horses compared with competition horses (OR 2.9; 95% CI 1.5–5.5, P = 0.002).Conclusion and practical significanceIdentification of breed and other horse characteristics as risk factors for obesity will enable optimal targeting of owner education regarding preventive management to reduce the risk of obesity among the British horse population.Ethical animal researchOwner informed consent was obtained for the questionnaire. Sources of funding: This project was funded by World Horse Welfare. Competing interests: None.

Body Girth as an Alternative to Body Mass for Establishing Condition Indexes in Field Studies: A Validation in the King Penguin

Body mass and body condition are often tightly linked to animal health and fitness in the wild and thus are key measures for ecophysiologists and behavioral ecologists. In some animals, such as large seabird species, obtaining indexes of structural size is relatively easy, whereas measuring body mass under specific field circumstances may be more of a challenge. Here, we suggest an alternative, easily measurable, and reliable surrogate of body mass in field studies, that is, body girth. Using 234 free-living king penguins (Aptenodytes patagonicus) at various stages of molt and breeding, we measured body girth under the flippers, body mass, and bill and flipper length. We found that body girth was strongly and positively related to body mass in both molting (R(2) = 0.91) and breeding (R(2) = 0.73) birds, with the mean error around our predictions being 6.4%. Body girth appeared to be a reliable proxy measure of body mass because the relationship did not vary according to year and experimenter, bird sex, or stage within breeding groups. Body girth was, however, a weak proxy of body mass in birds at the end of molt, probably because most of those birds had reached a critical depletion of energy stores. Body condition indexes established from ordinary least squares regressions of either body girth or body mass on structural size were highly correlated (r(s) = 0.91), suggesting that body girth was as good as body mass in establishing body condition indexes in king penguins. Body girth may prove a useful proxy to body mass for estimating body condition in field investigations and could likely provide similar information in other penguins and large animals that may be complicated to weigh in the wild.

Morphometric indices of body condition in birds: a review

Morphometric estimates of body condition are widely used by ornithologists, but which estimates work best is a matter of debate. We review morphometric approaches (body mass, ratio and residual condition indices, predictive regression models, fat scoring, and abdominal profiles) for estimating body condition (defined as fat mass) in birds. We describe the strengths and weaknesses of each approach. Across diverse indices and species (~200 estimates total), the mean r 2 relating condition indices to mass of body fat was 0.55, and 64% of the r 2 values were greater than 0.50. But despite their generally good performance, condition indices sometimes perform poorly (i.e., r 2 is low). The data indicate that: (1) no single index was clearly best, (2) on average body mass alone, fat scores, and predictive multiple regression equations explained slightly more than 50% of the variation in fat content, (3) on average, ratio and residual indices explained slightly less than 50% of the variation in fat content, and (4) body mass alone, a variable that can be easily and reliably measured, is as good or nearly as good an indicator of fat content as any other condition index. We recommend that: (1) morphometric indicators of condition be empirically validated, (2) researchers publish their body composition data in sufficient detail that they can be used in future analyses exploring the relative merits of different condition indices, and (3) multiple regression directly on measured traits be used instead of condition indices whenever the condition index is not empirically validated.

New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method

Body condition is assumed to influence an animal's health and fitness. Various non‐destructive methods based on body mass and a measure of body length have been used as condition indices (CIs), but the dominant method amongst ecologists is currently the calculation of residuals from an ordinary least squares (OLS) regression of body mass against length. Recent studies of energy reserves in small mammals and starlings claimed to validate this method, although we argue that they did not include the most appropriate tests since they compared the CI with the absolute size of energy reserves. We present a novel CI (the ‘scaled mass index’) based on the central principle of scaling, with important methodological, biological and conceptual advantages. Through a reanalysis of data from small mammals, starlings and snakes, we show that the scaled mass index is a better indicator of the relative size of energy reserves and other body components than OLS residuals, performing better in all seven species and in 19 out of 20 analyses. We also present an empirical and theoretical comparison of the scaled mass index and OLS residuals as CIs. We argue that the scaled mass index is a useful new tool for ecologists.

A reliable body condition scoring technique for estimating condition in African buffalo

AbstractEvaluating animal body condition is a necessary component of many ecological studies. Although many methods for assessing animal body condition have been developed, relatively few can be used for estimating condition on live animals. Noninvasive body condition scoring techniques have been developed for assessing condition in livestock and more recently such techniques have been applied to wild ungulates. In this study, we examined the reliability of a body condition scoring technique for assessing condition in African buffalo (Syncerus caffer caffer). We compared a body condition score (BCS) based on visual assessment and manual palpation of an animal’s body to two standard metrics of condition widely used in mammals: kidney fat index (KFI) and haematocrit (HCT). Across all buffalo, BCS was significantly and positively correlated with both KFI and HCT. For HCT, this pattern was observed among adults, juveniles, males and females; and in the wet season but not in the dry season. For KFI, BCS was significantly and positively correlated with KFI among adults, juveniles and males, but not in females. Overall, our results suggest that the BCS technique can serve as a useful method for estimating body condition in buffalo.

Approaches to estimate body condition from slaughter records in reindeer

Long-term fluctuations in population densities of reindeer and caribou are common, where pasture is the limiting resource. Pasture quality affects the nutritional status and production of the animals. Therefore, continuous information about changes in the grazing resources is important when making management decisions. The objective of this study was to investigate different possibilities of using routine and additional slaughter records as body condition indicators, and thereby indicators of pasture resources in the summer ranges of reindeer husbandry. Records from 696 reindeer slaughtered in the winter 2002/2003 were included in the study. We developed a model with carcass weight as body condition indicator and two different models combining fatness, conformation, carcass weight, and body size as body condition indicators. The results showed age and sex dependent differences between the variables, and differentiation of animal age and sex improved the precision of models. Adjusting weight for body size also improved weight as a body condition indicator in adults. Conformation and fatness had good resemblance to weight and body size adjusted weight and should preferably be included, together with carcass weight and body size measures, when estimating body condition from carcasses. Our analysis showed that using non-invasive slaughter records is a good and non-expensive method of estimating body condition in reindeer. Abstract in Swedish / Sammandrag:Tillvägagångssätt för skattning avkroppskondition hos ren från slaktregistreringarFluktuationer i ren- och caribou-populationers täthet över tiden är vanliga då betet är en begränsad resurs och beteskvalitén påverkar djurens kondition och produktion. Kontinuerligt uppdaterad information om förändringar i betesresurserna är viktigt i samband med beslutsfattande om förvaltning avresurserna. Syftet med denna studie var att utvärdera olika möjliga sätt att använda rutinregistreringar och extra registreringar vid slakt som konditionsindikatorer och därmed indikatorer för betestillstånd i sommarland inom rennäringen. Registreringar från 696 renar, slaktade under säsongen 2003/2003 användes i studien. Vi utvecklade en modell där slaktvikt var den enda indikatorn på kroppskondition, samt två modeller som kombinerade fett- och formklassificeringen med slaktvikt och kroppsstorlek som indikatorer på kroppskondition. Resultaten visade att renarnas ålder och kön ger skillnader i de olika variablerna och att modellernas noggrannhet ökar om djuren grupperas med tanke på ålder och kön. Att korrigera slaktvikten för kroppsstorlek ökade precisionen för vikt som konditionsindikator för vuxna djur. Fett- och formklassificeringen överensstämde väl med storlekskorrigerad slaktvikt och skulle med fördel kunna inkluderas tillsammans med slaktvikt och storlek för skattning avkroppskondition från slaktkroppar. Våra analyser visar att användning avslaktregistreringar är en bra och billig metod för att skatta kroppskonditionen hos renhjorden.

Analysing body condition: mass, volume or density?

1. Body condition (defined as the relative amount of energy reserves in the body) is an animal trait with strong ecological implications. In some animal taxa (e.g. arthropods), the external volume of the body part in which most nutrients are stored (e.g. abdomen) is used interchangeably with body mass to estimate body condition, making the implicit assumption that abdomen residual volume is a good surrogate of residual mass. However, the degree of correlation between these two measures should largely depend on the density of the nutrients stored. 2. We simulated two food-supplemented experimental groups of animals, each storing a slightly different amount of lipids either in their abdomens or in their entire bodies, and explored (i) how different estimates of condition were able to detect fixed differences between the groups; and (ii) how the amount of lipids stored could affect the outcome of non-intrusive measures of condition on a dichotomous variable (e.g. survival, mating success). We found that density body condition (body mass statistically controlled for structural body size and body volume) has much greater power to detect differences between experimental groups or effects on binary response variables than do classic mass/size or volume/size condition indices. 3. Using data on Lycosa tarantula (L.), a burrowing wolf spider, we report dramatic differences among these three indices in their ability to detect sex differences in the effect of feeding treatment on body condition at maturity. In particular, a plot of residual mass against residual volume reflecting nutrient density suggests that poorly fed spiders are nutritionally unbalanced, since well-fed spiders invest in nutrients of very different density. 4. Furthermore, using data on Scathophaga stercoraria (L.), the yellow dung fly, we found that an index of density condition was better at distinguishing condition differences among three populations than were mass or volume condition estimates alone. 5. We propose that including these three surrogates of condition (mass, volume and density) will substantially improve the accuracy of non-intrusive estimates of body condition, thus providing more powerful tools with direct application in a wide range of disciplines.

The value of bioelectrical impedance analysis vs. condition indices in predicting body fat stores in North American porcupines (Erethizon dorsatum)

We developed a predictive model to estimate body fat stores in a population of North American porcupines, Erethizon dorsatum (L., 1758). We trapped porcupines in the autumn of 2004 and spring of 2005. After collecting morphometric measurements on each animal, we used a plethysmograph to perform bioelectrical impedance analysis (BIA). We euthanized the subjects, measured two components of body composition (body fat, body water) via direct chemical analysis, and calculated lean dry mass to compare with BIA data. With regression we found the best predictive models for total body water, total body fat, percent body fat, and lean dry mass. We also estimated body condition for each animal using six different condition indices and compared the ability of the condition indices and our regression model to predict total body fat. Our model for total body fat accounted for 84% of the variation in fat measured by direct chemical analysis, and our model for percent body fat accounted for 78% of the variation. Two condition indices were significantly related to total body fat in porcupines and explained 45%–49% of the variation in observed body fat. We recommend BIA as a useful technique for estimating body fat stores in field studies of free-ranging porcupines and suggest abandonment of the use of condition indices as analogues of body fat stores in animal studies unless the indices can first be validated.

CONDITION INDICES AND BIOELECTRICAL IMPEDANCE ANALYSIS TO PREDICT BODY CONDITION OF SMALL CARNIVORES

Abstract Body condition directly affects survival and reproduction by animals, so its effects on fitness represent an important component of animal ecology. Traditionally, ecologists have relied on direct chemical analysis or morphometric indices to assess body condition. We examined the ability of morphometric indices and bioelectrical impedance analysis to estimate body condition of raccoons (Procyon lotor) and assessed the need for species-specific models. Morphological indices were poor estimators of body condition; the best model explained 62% of the variation of fat and had a high SE (r2 = 0.62, SE = 0.52, P < 0.001). Bioelectrical impedance analysis proved to be a reliable way to noninvasively estimate body condition. Models for lean dry mass and total body water were used to accurately estimate body fat (r2 = 0.94, SE = 0.16, P < 0.001). Body fat estimates derived through models for a similar species performed better than morphometric indices but did not achieve the accuracy of the species-specifi...

Short‐ and long‐term consequences of thermal variation in the larval environment of anurans

1. To survive adverse or unpredictable conditions in the ontogenetic environment, many organisms retain a level of phenotypic plasticity that allows them to meet the challenges of rapidly changing conditions. Larval anurans are widely known for their ability to modify behaviour, morphology and physiological processes during development, making them an ideal model system for studies of environmental effects on phenotypic traits. Although temperature is one of the most important factors influencing the growth, development and metamorphic condition of larval anurans, many studies have failed to include ecologically relevant thermal fluctuations among their treatments. 2. We compared the growth and age at metamorphosis of striped marsh frogs Limnodynastes peronii raised in a diurnally fluctuating thermal regime and a stable regime of the same mean temperature. We then assessed the long-term effects of the larval environment on the morphology and performance of post-metamorphic frogs. 3. Larval L. peronii from the fluctuating treatment were significantly longer throughout development and metamorphosed about 5 days earlier. Frogs from the fluctuating group metamorphosed at a smaller mass and in poorer condition compared with the stable group, and had proportionally shorter legs. 4. Frogs from the fluctuating group showed greater jumping performance at metamorphosis and less degradation in performance during a 10-week dormancy. Treatment differences in performance could not be explained by whole-animal morphological variation, suggesting improved contractile properties of the muscles in the fluctuating group.

Body Condition in the Eurasian Woodcock Wintering in the West of France: Practical Study for Wildlife Management during Cold Spells

The Eurasian woodcock ( Scolopax rusticola ) is one of the most widespread species of the Scolopax genus in temperate regions. However, population levels can be greatly affected by harsh cold spells that led woodcocks to starve by exhaustion of their body fuels. To better understand the vulnerability of woodcocks to such climatic conditions it is of a major importance to determine the amount of their body reserves (both lipids and proteins) throughout the wintering season. This was performed on 55 individuals collected by hunters in the western part of France during two consecutive winters under mild weather conditions. Body reserves, that can be mobilised, were determined as the difference between the total amount of lipids and proteins minus the values obtained on starved individuals found dead during previous cold spells. Overall, body reserves did not significantly change over both winters (p > 0.40), the maximal mean value (1539 ± 117 kJ) being however reached in January. Storing body fuels would not adversely affect wing and power loading, suggesting that the amount of body reserves would agree with the starvation-predation trade-off. If woodcocks sit through a cold spell, their mean survival time (or fasting endurance) would be 6.5 ± 0.5 days; 25 to 40% of the birds would have a life expectancy of 7-9 days, and about 8 to17% less than 5 days. On the contrary, if woodcocks immediately leave their wintering quarter, they would be able to perform a trip of 740 ± 50 km, 20 to 40% of the woodcocks being able to fly over 750 km. Body mass explains only 47 to 57% of the fasting endurance and flight autonomy variations, and therefore we recommend a further carcass analysis to accurately estimate body condition. These results underscore the suitability of determining the state of body reserves for practical cases of population management and hunting policy during cold spells.

Total body electrical conductivity (TOBEC) measurements in Mongolian gerbils (Meriones unguiculatus) and golden hamsters (Mesocricetus auratus)

Summary Body composition of adult Mongolian gerbils (Meriones unguiculatus) and golden hamsters (Mesocricetus auratus) was determined using the non-invasive measurement of the total body electrical conductivity (TOBEC). A regression model was developed based on direct chemical analysis of the carcass and calibration equations were defined to predict the fat-free mass (FFM) and the total body water (TBW) in these two species. The closest correlation was obtained by calculating a linear regression of FFM and TBW as a function of TOBEC: gerbils: FFM (g) = 0.20548 × TOBEC + 10.0224; TBW (g) = 0.14485 × TOBEC + 6.51824; golden hamsters: FFM (g) = 0.18043 × TOBEC + 18.5806; TBW (g) = 0.14817 × TOBEC + 4.50379. Based on these equations and the respective TOBEC values, the body composition was analysed. Male golden hamsters had a higher crude fat mass (CFM, obtained by substracting the FFM from the body mass) and a higher dried body mass (DBM, obtained by substracting the TBW from the body mass) than females, which had a higher percentage of FFM and TBW. In Mongolian gerbils, males had higher CFM, higher DBM and the absolute FFM and TBW was elevated. As in female golden hamsters, female gerbils had a higher percentage of FFM and TBW. Results are discussed in relation to the usefulness of this non-invasive technique, which allows repeated individual measurements of body composition. It helps to reduce the number of animals necessary when estimating body condition and welfare issues, male/female differences or for the evaluation of seasonal effects and housing conditions.

A potential multivariate index of condition for small mammals

Body condition in small mammals is often investigated by examining the residuals of a regression of mass on a linear measure of body size. Such indices include a number of assumptions, which, in most cases, are not tested. This study presents a residual condition index, that uses the regression of body mass on the Axis 1 factor scores from a Principal Components Analysis, to estimate body condition in free‐living ship rats, Rattus rattus Linneaus 1758, caught in mixed forest in New Zealand. The results from this index and a simpler ratio index were compared to determine how well they met the assumptions of the technique, and how well they identified biological differences in the population. Of the indices tested, the residual index based on an Ordinary Least Squared regression proved to be the most statistically robust method. The condition indices calculated were probably correlated with significant differences between individuals, but were not compared with true condition as estimated by fat reserves. Further applications and the need for the validation of the residual index are discussed.

A comparison of techniques used to estimate body condition of southern elephant seals (Mirounga leonina)

The total body water (TBW) and body condition of 86 female southern elephant seals was estimated from tritiated water (HTO) dilution space analysis. HTO blood samples were analysed using two distillation methods (direct serum counts and evaporative freeze capture) that yielded significantly different estimates. Evaporative freeze capture is recommended for use because it is faster, cheaper, and provides a more precise TBW estimate of dilution space. Estimates of TBW were then compared with those derived from bioelectrical impedance analysis (BIA) and morphometric models. There were significant, positive relationships between TBW and BIA variables, but the level of accuracy was inadequate for BIA to be more useful than the other methods trialled. Morphometric models accurately estimated TBW (kg). Models developed from surface area (SA) (TBW = [SA * 82.58] – 86.94) and from a combination of mass (M), length (L), and girth (G) (TBW = [(M * 0.72) + (L * 5.49) + (G * 134.94) + 164.36)] provided the most accurate TBW estimates. In contrast, condition indices did not give accurate or reliable estimates of relative body condition.