Mineral density and biomechanical properties of bone tissue from male Arctic foxes (Vulpes lagopus) exposed to organochlorine contaminants and emaciation

We investigated the impact from dietary OC (organochlorine) exposure and restricted feeding (emaciation) on bone mineral density (BMD; g hydroxy-apatite cm(-2)) in femoral, vertebrate, skull and baculum osteoid tissue from farmed Arctic blue foxes (Vulpes lagopus). For femur, also biomechanical properties during bending (displacement [mm], load [N], energy absorption [J] and stiffness [N/mm]) were measured. Sixteen foxes (EXP) were fed a wet food containing 7.7% OC-polluted minke whale (Balaenoptera acutorostrata) blubber in two periods of body fat deposition (Aug-Dec) and two periods of body fat mobilisation (Jan-July) in which the food contained less energy and only 2% blubber. SigmaOC food concentration in the food containing 7.7% whale blubber was 309 ng/g wet mass. This corresponded to a SigmaOC exposure of ca. 17 microg/kg body mass/d and a responding SigmaOC residue in subcutaneous adipose tissue of ca. 1700 ng/g live mass in the 8 EXP fat foxes euthanized after 16 months. A control group (CON) composed of 15 foxes were fed equal daily caloric amounts of clean pork (Sus scrofa) fat. After 16 months, 8 EXP and 7 CON foxes were euthanized (mean body mass=9.25 kg) while the remaining 8 EXP and 8 CON foxes were given restricted food rations for 6 months resulting in a body weight reduction (mean body mass=5.46 kg). The results showed that only BMD(skull) vs. BMD(vertebrae) were significantly correlated (R=0.68; p=0.03; n=10) probably due to a similar composition of trabecular and cortical osteoid tissue. No difference in any of the BMD measurements or femoral biomechanical properties was found between EXP and CON foxes although BMD baculum was 1.6-folds lower in the EXP group. However, lean summer foxes had significantly lower femoral biomechanical properties measured as displacement (mm), energy absorption (J) and time (s) biomechanical properties than fat winter foxes (all p<0.004). This indicates lower stiffness and softer bones from fasting which is in agreement with previous studies. Further, it should be kept in mind when studying bone tissues in Arctic mammals also in order to avoid confounding effects from body condition.     

Evaluation of a Quantitative Magnetic Resonance Imaging System for Whole Body Composition Analysis in Rodents

We evaluated the EchoMRI‐900 combination rat and mouse quantitative magnetic resonance (QMR) body composition method in comparison to traditional whole‐body chemical carcass composition analysis (CCA) for measurements of fat and fat‐free mass in rodents. Live and postmortem (PM) QMR fat and lean mass measurements were obtained for lean, obese and outbred strains of rats and mice, and compared with measurements obtained using CCA. A second group of rats was measured before and after 18 h food or water deprivation. Significant positive correlations between QMR and CCA fat and lean mass measurements were shown for rats and mice. Although all live QMR fat and lean measurements were more precise than CCA for rats, values obtained for mice significantly differed from CCA for lean mass only. QMR performed PM slightly overestimated fat and lean values relative to live QMR but did not show lower precision than live QMR. Food deprivation reduced values for both fat and lean mass; water deprivation reduced estimates of lean mass only. In summary, all measurements using this QMR system were comparable to those obtained by CCA, but with higher overall precision, similar to previous reports for the murine QMR system. However, PM QMR measurements slightly overestimated live QMR values, and lean and fat mass measurements in this QMR system are influenced by hydration status and animal size, respectively. Despite these caveats, we conclude that the EchoMRI QMR system offers a fast in vivo method of body composition analysis, well correlated to but with greater overall precision than CCA.     

Accuracy and precision of dual-energy X-ray absorptiometry for body composition measurements in rhesus monkeys

Accuracy of body composition measurements by dual-energy X-ray absorptiometry (DXA) was compared with direct chemical analysis in 10 adult rhesus monkeys. DXA was highly correlated (r-values > 0.95) with direct analyses of body fat mass (FM), lean mass (LM) and lumbar spine bone mineral content (BMC). DXA measurements of total body BMC were not as strongly correlated (r-value = 0.58) with total carcass ash content. DXA measurements of body FM, LM and lumbar spine BMC were not different from data obtained by direct analyses (P-values > 0.30). In contrast, DXA determinations of total BMC (TBMC) averaged 15%, less than total carcass ash measurements (P = 0.002). In conclusion, this study confirms the accurate measurement of fat and lean tissue mass by DXA in rhesus monkeys. DXA also accurately measured lumbar spine BMC but underestimated total body BMC as compared with carcass ash determinations.     

Validating Predictive Models of Nutritional Condition for Mule Deer

Abstract: We developed new, and validated existing, indices of nutritional condition for live and dead mule deer (Odocoileus hemionus). Live animal indices included a body condition score (BCS), thickness of subcutaneous fat and selected muscles using ultrasonography, and body mass. Dead animal indices included femur, metatarsal, and mandible marrow fat, 3 kidney fat indices, and 2 carcass scoring methods. We used 21 female deer and 4 castrates (1-11 yr old) varying widely in nutritional condition (2-28% ingesta-free body fat). Deer were euthanized and homogenized for chemical analysis of fat, protein, water, and ash content. Estimates of fat and gross energy (GE) were regressed against each condition indicator using regression. Subcutaneous fat thickness, a rump BCS, and rLIVINDEX (an arithmetic combination of subcutaneous fat thickness and the rump BCS) were most related to condition for live animals (r² ≥ 0.87, P < 0.001) whereas the Kistner score and kidney fat were most related to fat and GE for dead animals (r² ≥ 0.77, P < 0.001). We also evaluated range of usefulness and sensitivity to small changes in body condition for all models. In general, indices with moderate or highly curvilinear statistical relations to body fat or those based on only one fat depot or a small number of ranking scores will have limitations in their use. Our results identify robust tools for a variety of research and monitoring designs useful for evaluating nutrition's effect on mule deer populations.     

A novel method to determine lean body water using localized skin biopsies: correlation between lean skin water and lean body water in an overhydration model

To determine the relationship between total body water (TBW) fraction and local water content measured in the skin (SW) this study assessed eight anesthetized piglets in an overhydration model. TBW was assessed by deuterium oxide dilution and body mass measurements taken throughout the experiments, and by whole body carcass analysis at the end of each experiment. Additionally, extracellular water and plasma volume were assessed using bromide dilution and Evan's blue dilution, respectively. SW was assessed by tissue biopsies taken at 60-min intervals throughout the experiment. Lean body water (LBW) fraction and lean skin water (LSW) fraction were assessed by extracting the fat from the carcass and biopsy samples. A correlation does exist between TBW fraction and SW fraction with r2=0.58 (P<0.05); however, the strongest correlation occurred between the LBW fraction and LSW fraction with r2=0.87 (P<0.05) and an SE of prediction of 0.77%. These data demonstrate that LSW gives an accurate and precise estimate of LBW and could therefore be used to determine the hydration index in appropriate research settings.     

Content and deposition of major mineral elements in different tissues and empty body of growing bulls of the german simmental breed

54 bulls of the German Simmental breed were fed either on a high energy level (maize silage ad libitum and 1.8 kg concentrate) or on a low energy level (maize silage restrictively and 1.0 kg concentrate). In dependence on feeding intensity a mean daily weight gain of 870 or 1210 g was obtained. Animals were slaughtered with a live mass of 200 kg, 350 kg, 500 kg, 575 kg and 650 kg. Empty body was divided into 13 cuts and afterwards separated into lean, bone and adipose tissues and tendons. Major mineral element content was determined in these tissues as well as in the noncarcass parts.

In the lean tissue the mean content (200 kg) of 0.3 g calcium, 10 g phosphorus, 1 g magnesium, 2.3 g sodium and 14.8 g potassium/kg dry matter decreased slightly with rising live mass (200–650 kg). The contents of major mineral elements were much higher in bone tissue. For the fattening period from 200 to 650 kg of live mass mean contents of 151.5 g calcium, 71.3 g phosphorus, 3.2 g magnesium, 5.1 g sodium and 1.1 g potassium per kg DM were analysed. Mineral element content of bone tissue increased with rising live mass as well as animals on low feeding intensity showed a higher mineral content than on high energy level. In all, major mineral element content in fat tissue was very low. In noncarcass parts head and legs calcium and phosphorus had analogous to bone tissue the highest concentration. Hide showed a high content of sodium, whereas organs and digestive tract had a high content of potassium and phosphorus. Total mass of major mineral elements in the different tissues increased above all in the fattening period of 200 to 350 kg. In carcass as well as in empty body, mass of calcium and phosphorus was much higher than magnesium, sodium and potassium. Also animals on low feeding intensity showed a higher mass of major mineral elements in carcass and empty body than animals on high energy feeding intensity. The intensively fed bulls had a mean deposition of 12.7 g calcium, 6.9 g phosphorus, 0.37 g magnesium, 1.2 g sodium and 2.1 potassium per 1000 g of empty body weight gain, whereas restrictively fed bulls deposited in average 15.0 g calcium, 7.8 g phosphorus, 0.4 g magnesium, 1.2 g sodium and 2.4 g potassium per 1000 g of empty body weight gain.     

Estimation of carcass composition and cut composition from computed tomography images of live growing pigs of different genotypes

The aim of the present work was (1) to study the relationship between cross-sectional computed tomography (CT) images obtained in live growing pigs of different genotypes and dissection measurements and (2) to estimate carcass composition and cut composition from CT measurements. Sixty gilts from three genotypes (Duroc×(Landrace×Large White), Pietrain×(Landrace×Large White), and Landrace×Large White) were CT scanned and slaughtered at 30 kg (n=15), 70 kg (n=15), 100 kg (n=12) or 120 kg (n=18). Carcasses were cut and the four main cuts were dissected. The distribution of density volumes on the Hounsfield scale (HU) were obtained from CT images and classified into fat (HU between −149 and −1), muscle (HU between 0 and 140) or bone (HU between 141 and 1400). Moreover, physical measurements were obtained on an image of the loin and an image of the ham. Four different regression approaches were studied to predict carcass and cut composition: linear regression, quadratic regression and allometric equations using volumes as predictors, and linear regression using volumes and physical measurements as predictors. Results show that measurements from whole animal taken in vivo with CT allow accurate estimation of carcass and cut composition. The prediction accuracy varied across genotypes, BW and variable to be predicted. In general, linear models, allometric models and linear models, which included also physical measurements at the loin and the ham, produced the lowest prediction errors.     

Predicting the chemical composition of the body and the carcass of hair sheep using body parts and carcass measurements

Determination of the chemical composition in the body and carcass of ruminants is important for both nutritional requirement studies and the meat industry. This study aimed to develop equations to predict the body and carcass chemical composition of hair sheep using the chemical composition of body parts, carcass measurements and shrunk BW as predictors. A database containing 107 individual records for castrated male hair sheep ranging from 24 to 43 kg BW was gathered from two body composition studies. The empty body, carcass and body parts were analyzed for water, ash, fat and protein contents (%). The body parts used to estimate body and carcass composition were fore leg, hind leg and 9–11th rib section. The carcass measurements used were leg length, thoracic circumference, hind circumference, hind width, thoracic width, thoracic depth and chest width. Each model performance was evaluated using a leave-one-out cross-validation. Multiple regression analysis considering the study as a random effect revealed that body parts in association with carcass measurements were significant for predicting the chemical composition in the body of castrate male sheep. However, the use of the chemical composition of hind leg produced the best models for predicting the ash and fat contents in the empty body, whereas the water and protein contents in the empty body were better predicted when using the chemical compositions of 9–11th rib section and fore leg, respectively. Multiple regression analysis also revealed that most body parts were suitable for predicting the carcass composition, except for 9–11th rib section whose chemical composition did not produce significant prediction equations for ash and protein carcass contents. The use of the chemical composition of hind leg in association with carcass measurements produced the best models for predicting the water and fat contents in the carcass, while the ash and protein contents in the carcass were better predicted when using the chemical composition of fore leg. In conclusion, precision, accuracy and goodness-of-fit of the equations drove the selection of the chemical composition of hind leg and carcass measurements in a multivariate approach, as the most suitable predictors of the chemical composition of the body and carcass of hair sheep. However, the chemical composition of fore leg may be used as well. The developed equations could improve the accuracy of the empty body and carcass composition estimations in sheep, optimizing the estimation of nutrient requirements, as well as the carcass quality evaluation for this species.     

Evaluation of the deuterium dilution method to estimate body composition in the barnacle goose: accuracy and minimum equilibration time

We examined body composition in barnacle geese (Branta leucopsis) by proximate carcass analysis and by deuterium isotope dilution. We studied the effect of isotope equilibration time on the accuracy of total body water (TBW) estimates and evaluated models to predict fat-free mass (FFM) and fat mass (FM) from different measurements varying in their level of invasiveness. Deuterium enrichment determined at 45, 90, and 180 min after isotope injection did not differ significantly. At all sampling intervals, isotope dilution spaces (TBW(d)) consistently overestimated body water determined by carcass analysis (TBW(c)). However, variance in the deviation from actual TBW was higher at the 45-min sampling interval, whereas variability was the same at 90 and 180 min, indicating that 90 min is sufficient time to allow for adequate equilibration. At 90 min equilibration time, deuterium isotope dilution overestimated TBW(c) by 7.1% +/= 2.6% (P < 0.001, paired t-test, n=20). This overestimate was consistent over the range of TBW studied, and TBW(c) could thus be predicted from TBW(d) (r2=0.976, P<0.001). Variation in TBW(c) and TBW(d) explained, respectively, 99% and 98% of the variation in FFM. FM could be predicted with a relative error of ca. 10% from TBW estimates in combination with body mass (BM). In contrast, BM and external body measurements allowed only poor prediction. Abdominal fat fresh mass was highly correlated to total FM and, if the carcass is available, allows simple means of fat prediction without dissecting the entire specimen.     

Determining body fuels of wintering mallards

Measuring body lipids and proteins of wild animals such as mallards is essential to determine the impact of the environment on their body condition. A major difficulty, however, is that biochemical analysis of carcass is tedious and therefore cannot be applied at a large scale. The main objective of this study was therefore to find out if simple measurements can be used as indices of total body lipids and proteins. Four classes of lipid and protein indices, derived on a 'source' group, were defined according to their complexity and condition of application (field or laboratory). Accuracy of the indices was evaluated on an independent group, of which the body composition calculated from indices was compared to carcass analysis. In live birds, body mass was an accurate and convenient predictor for both lipid and protein masses. If carcasses are available, extensive analysis provides a higher accuracy for body lipids only. This can be simply obtained through multiple regressions using abdominal fat mass and/or dry body mass.     

Estimation of carcass fat and protein in northern pintails (Anas acuta) during spring migration

Foraging in stopover areas influences nutritional condition of birds during spring migration. Our purpose was to determine if body mass, percent carcass water, and serum biochemistry would predict energy reserves (carcass fat and protein) in northern pintails (Anas acuta) at a spring staging area, Lake St. Pierre in Québec, Canada (46 degrees 11 'N, 73 degrees 08 'W). Northern pintails were collected during spring 1997 (14 April-9 May). In this staging area, body mass and percent body water successfully estimated carcass protein and fat in male northern pintails, but only carcass protein in females. None of the seven blood parameters we used accurately estimated nutritional reserves in staging northern pintails. These findings suggest that investigators must use direct estimates of carcass reserves to examine nutrient reserve requirements for egg production, migration, or body maintenance during spring migration.     

Noninvasive estimation of body composition in small mammals: a comparison of conductive and morphometric techniques

Body fat stores may serve as an index of condition in mammals. Thus, techniques that measure fat content accurately are important for assessing the ecological correlates of condition in mammal populations. We compared the ability of two conductive techniques, bioelectrical impedance analysis (BIA) and total body electrical conductivity (TOBEC), to predict body composition with that of morphometric methods in three small mammal species: red squirrels (n=13), snowshoe hares (n=30), and yellow-bellied marmots (n=4). Animals were livetrapped in northern Idaho; BIA (all subjects) and TOBEC (squirrels only) measurements were taken following chemical immobilization in the field, and morphometric measurements were taken postmortem. Information provided by BIA and TOBEC failed to improve upon the predictive power of morphometric equations for total body water (TBW) and lean body mass (LBM) in squirrels and hares, which do not store substantial amounts of fat (<5% body mass comprised of fat). Although the same pattern held with respect to LBM in marmots, which accumulate substantial amounts of body fat (>10% body mass), a BIA-based model proved best at estimating TBW, suggesting that the usefulness of conductive techniques may be a function of fat deposition. However, regardless of the technique used to predict body composition, estimates of body fat furnished by our equations failed to approximate actual fat levels accurately in all three test species, probably because these techniques only provide indirect estimates of fat content. These results highlight the limitations inherent in contemporary methods of animal fat estimation and underscore the need for the development of direct and accurate measures of body fat in mammals.     

Effects of carrion resources on herbivore spatial distribution are mediated by facultative scavengers

Carcasses of large herbivores are pulsed resources whose impact on animal communities and ecological processes is poorly understood. In temperate forests, long-lasting ungulate carcasses are a prime resource for many species of birds and mammals during winter. Facultative carrion-eaters also consume live prey, thus potentially leading to unexpected secondary effects on populations of species not directly linked to carcass exploitation. By snow-tracking and direct observations we investigated in Bia?owie?a Forest (E. Poland) whether large ungulate carcasses elicit spatial responses in facultative scavengers and their prey. We found that in the vicinity of carcass sites the probability of the presence of common ravens Corvus corax, jays Garrulus glandarius and red foxes Vulpes vulpes increased significantly. Indeed, large groups of the two bird species were exclusively found in those places. Because of these aggregations, the probability of predator–prey encounters (red foxes and brown hares Lepus europaeus) was significantly higher near carcass sites. Accordingly, the abundance of hares and other live prey such as red squirrels Sciurus vulgaris decreased at their vicinities, probably as a consequence of direct killing and/or predator avoidance. This study provides the first evidence of carrion pulses permeating into apparently distant trophic levels, such as herbivores, via facultative scavengers, thus highlighting some unnoticed but relevant effects of carrion resources on community structure.     

Persistence of antibodies in blood and body fluids in decaying fox carcasses, as exemplified by antibodies against Microsporum canis

To assist in evaluating serological test results from dead animals, 10 silver foxes (Vulpes vulpes) and 10 blue foxes (Alopex lagopus), 6 of each species previously vaccinated against and all challenged with Microsporum canis, were blood sampled and euthanased. Fox carcasses were stored at +10°C, and autopsy was performed on Days 0, 2, 4, 7, and 11 post mortem during which samples from blood and/or body fluid from the thoracic cavity were collected. Antibodies against M. canis were measured in an enzyme-linked immunosorbent assay (ELISA) as absorbance values (optical density; OD). To assess the degradation of antibodies, the ratio between post mortem and ante mortem absorbance was calculated. The mean absorbance from samples collected during autopsy was generally lower than from samples from live animals. In blood samples, this difference increased significantly with time (P = 0.04), while in body fluid samples the difference decreased (not significant; P = 0.18). We suggest that a positive serological result from testing blood or body fluid of a dead animal may be regarded as valuable, although specific prevalences obtained by screening populations based on this type of material may represent an under-estimation of the true antibody prevalence. Negative serological test results based on material from carcasses may be less conclusive, taken into account the general degradation processes in decaying carcasses, also involving immunoglobulin proteins.     

Gender and slaughter weight effects on carcass quality traits of suckling lambs from four different genotypes

The effects of gender and slaughter weight on carcass quality traits were studied in 114 suckling lambs from four genotypes (Suffolk Down, Merino Precoz Aleman, Suffolk Down × Corriedale and Suffolk Down × Merino Precoz Aleman) raised to either 10 or 15 kg live weight. The characteristics of hot carcass weight, commercial dressing percent and real dressing percent (based on empty body weight), ribeye muscle area, and back fat depth were increased by higher slaughter weight; hot carcass weight, ribeye muscle area and back fat depth were higher in male suckling lambs. Different tissue components (bone, residues) varied according to slaughter weight. The commercial yield of carcass cuts and the anatomical proportions of shoulder and leg components were affected by both genotype and slaughter weight. None of the genotypes showed clearly superior carcass traits.     

Raising young reduces body condition and fat stores in black-legged kittiwakes

We conducted a manipulative experiment to investigate how raising chicks affects the body condition (body mass scaled by body size) and body composition (percent fat vs. lean mass) of black-legged kittiwakes (Rissa tridactyla). For 4 consecutive years (1991–1994) we removed eggs from randomly selected nests and then compared adults raising chicks with adults that had their eggs removed. At the end of the chick-rearing period, adults raising chicks were significantly lighter for their size than adults that had their eggs removed. Adults raising chicks also had a significantly lower percent body fat (by 28%) than adults from manipulated nests. The difference in percent body fat between the two groups was apparent at all levels of condition, suggesting that adults that are raising chicks apportion their reserves differently than adults that are working only to meet their own metabolic needs. End-of-season body condition of adults from manipulated and unmanipulated nests varied significantly among 5 years of study, and appeared to reflect differences in local foraging conditions. In all years, females were in worse condition than males at the end of the breeding season. This sex-specific condition difference did not, however, appear to indicate a greater short-term reproductive cost among females. Females were lighter for their size than males in both the manipulated and unmanipulated groups. Our results suggest that adult kittiwakes compromise their body condition and body composition during chick rearing to increase the likelihood of successfully fledging young, even though such adjustments may decrease their own post-reproductive survival probabilities. Prior to estimating the body composition of the experimental birds, we evaluated the usefulness of several noninvasive techniques for predicting fat mass in kittiwakes. We used cross-validation techniques to compare multiple regression models that included total body electrical conductivity (TOBEC), total body water (TBW), and morphometric measurements as independent variables. The most parsimonious model for predicting fat mass was based on TOBEC and mass measurements. TBW and morphometrics were of little utility in predicting fat mass in kittiwakes. Previous studies that have evaluated the usefulness of TOBEC as a predictor of fat mass have shown mixed results. We suggest that the size of the experimental subject relative to the size of the TOBEC measurement chamber may affect the accuracy of this technique. Received: 30 November 1998 / Accepted: 29 April 1999     

Estimating lipid and lean body mass in small passerine birds using TOBEC,external morphology and subcutaneous fat‐scoring

To assess regression models for lipid and lean body mass in small birds, we recorded live body mass ±0.1 g, total body electrical conductivity (TOBEC; from “third generation” TOBEC machine EM‐SCAN® SA‐3000) or E‐Value, visual fat score (VisFat), and seven body measurements for 52 migratory passerine birds of 13 species (5–40 g). We determined lipid and lean mass of each bird after petroleum‐ether extraction of lipids. We obtained “net”E‐Value (NEV) for each scanned bird by subtracting the E‐Value of the empty bird‐restraining tube, because these showed an inverse temperature dependence (P<0.005). Leave‐one‐out cross validation was used to assess model selection and construct 95% confidence intervals. Although precision of TOBEC increased with bird size (CV of NEV vs. live mass: r=−0.276, P=0.002) and it explained an increasing proportion of variation in lean mass moving from small‐ to medium‐ to large‐bird classes of our data, it did no better than head length in single‐variable prediction of lean or lipid mass and was included in five of the 14 multivariate models we developed. The best multiple regression to predict lean mass included live weight, VisFat, bill length, tarsus and lnNEV (adjusted R²=99.0%); however, the same model lacking only lnNEV yielded aR²=98.9%. A parallel to the above pair of models, but predicting lipid mass, yielded aR²=90.3% and 90.0%, respectively. Subdividing the data by three size classes and three taxa (American redstart Setophaga ruticilla, ovenbird Seiurus aurocapilla, warblers), best‐subset multiple‐regression models predicted lean mass with aR² from 94.7 to 99.6% and lipid mass with aR² from 85.4 to 98.3%. Best models for the size‐ and species‐groups included VisFat and zero to five body measurements, and most included live weight. lnNEV was included only in the models for ovenbird (lipid), warblers (lipid), all birds (both), and large birds (both). Actual lipid mass of all birds was more highly correlated with multiple‐regression‐predicted lipid mass (r=0.955) than with visual subcutaneous fat‐scoring (r=0.683). These multiple‐regression models predicting lipid content using live‐bird measurements and visual fat score as independent variables represent more accurate and precise estimates of actual lipid content in small passerines than any previously published. They are particularly accurate for placing birds into percentage body‐fat classes.     

Use of cold carcass weight and fat depth measurements to predict carcass composition of Rasa Aragonesa lambs

A total of 22 measurements of fat depth, taken along the 13th rib, 5–6th lumbar vertebra, 3–4th sacrum vertebra, and the 2nd, 2–3rd, 3rd, 3–4th, 4th, 4–5th sternebra of the breast bone, were taken on intact carcasses with a sharpened steel rule, and related to the carcass composition of 18 Rasa Aragonesa lambs. The objective was to study the accuracy of these different measurements for predicting carcass composition and possible value, in the process of carcass grading or classification of ‘Ternasco’ Aragón lambs. Cold carcass weight (CCW) accounted for 74% and 40% of the total variation of muscle weight and total carcass fat weight, respectively. The addition of 4 cm fat depth over the 13th rib from the left side accounted for a further 13% of muscle weight, and the addition of 4 cm fat depth over the 5–6th lumbar vertebra from the right side accounted for a further 29% of the variation of total carcass fat weight. Regarding different fat depots, CCW accounted for 49% and 31% of the total variation of the intermuscular fat and kidney and pelvic fat, respectively.

However, CCW alone only accounted for 21% (NS) of the total variation of subcutaneous fat weight, but the addition of 4 cm fat depth over the 13th rib from the right side or the addition of 4 cm fat depth over the 5–6th lumbar vertebra from the right side accounted for a further 47% of the subcutaneous fat variation. A comparison of the residual standard deviations (RSD) of the two measurements indicated that the fat depth over the 5–6th lumbar vertebra was more accurate for predicting subcutaneous fat. The highest precision, after CCW, for predicting intermuscular fat, was fat depth over the 13th rib from the left side, which accounted for a further 18% of total variation of this fat depot. Prediction of carcass composition was improved by the addition of fat depth measurements, assisting in the commercial classification of ‘Ternasco’ Aragón lambs.     

Survival and Cause-Specific Mortality of Red Foxes in Agricultural and Urban Areas of Illinois

Abstract: Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaike's Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0-20%) and high (80-100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40-70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May-Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.     

Evaluation of a Quantitative Magnetic Resonance Method for Mouse Whole Body Composition Analysis

Objective: To evaluate applicability, precision, and accuracy of a new quantitative magnetic resonance (QMR) analysis for whole body composition of conscious live mice. Research Methods and Procedures: Repeated measures of body composition were made by QMR, DXA, and classic chemical analysis of carcass using live and dead mice with different body compositions. Caloric lean and dense diets were used to produce changes in body composition. In addition, different strains of mice representing widely diverse populations were analyzed. Results: Precision was found to be better for QMR than for DXA. The coefficient of variation for fat ranged from 0.34% to 0.71% compared with 3.06% to 12.60% for DXA. Changes in body composition in response to dietary manipulation were easily detected using QMR. An increase in fat mass of 0.6 gram after 1 week (p < 0.01) was demonstrated in the absence of hyperphagia or a change in mean body weight. Discussion: QMR and DXA detected similar fat content, but the improved precision afforded by QMR compared with DXA and chemical analysis allowed detection of a significant difference in body fat after 7 days of consuming a diet rich in fat even though average body weight did not significantly change. QMR provides a very precise, accurate, fast, and easy‐to‐use method for determining fat and lean tissue of mice without the need for anesthesia. Its ability to detect differences with great precision should be of value when characterizing phenotype and studying regulation of body composition brought about by pharmacological and dietary interventions in energy homeostasis.