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PubMed1989

Body composition measurement by dual photon absorptiometry: comparison with body density and total body potassium measurements.

Body composition was measured in 29 healthy adults (12 men and 17 women) by three different methods: Dual photon (153Gd) absorptiometry (DPA), body density measurements (BD) and measurements of total body potassium (TBK). Correlation and regression analysis with the body fat percentage (Fat%) measured by the three different methods gave r values between 0.83 and 0.90 and SEEs between 4.0 and 6.0 (Fat%). We conclude that DPA provides a new method of measuring body composition with precision and accuracy errors in the same range as the more established methods.

Adult↗

PubMed1991

Genetic association of selection for increased leg muscle and increased shank diameter with body composition and walking ability.

Body compositions of a randombred control population (RBC2), a line selected for increased 16-wk BW (F), a line selected for increased shank diameter (FL), and a line selected for increased leg muscle mass (FM) were compared at 16 wk of age. The F line originated from the RBC2 population and the FL and FM lines were developed as sublines of the F line. The F and FL lines were developed through mass selection of BW and shank width, respectively. The FM line was developed through family selection for leg muscle mass. Selection for BW in the F line has resulted in an increase in the proportion of breast muscle and a decrease in the relative amount of leg bone in comparison with the RBC2 population. Selection for increased shank width in the FL line has increased not only shank weight but has produced concomitant increases in the weight of the tibiotarsal and femur bones. Although FL line has also shown a correlated increase in BW in association with increases in shank width the increase in leg bone weight was relatively greater than the increase in BW. Therefore, the relative weights of leg bones in the FL line increased such that they were more similar to the RBC2 population than to the F line. Although the amount of leg muscle increased slightly in the FM line, the relative proportion of leg muscle did not increase significantly. The selection program used was probably ineffective in increasing the proportion of leg muscle because of the high percentage (low selection intensity) of families selected and small family size for estimating family means.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1997

Anthropometry and body composition in children.

Changes in body fat, fat-free mass and extracellular water occur in many disorders, and during normal growth in children. Thus, body composition is an increasingly important measurement in paediatric clinical practice, and is used for diagnostic purposes, for decisions for treatment and for monitoring improvement. A number of different methods exist for determining body composition in children; however, their use is complicated by the absence of a gold standard and the lack of validity data in children both with and without growth disorders. In this report, validity and usefulness are compared among anthropometric methods and weighted against other techniques used in children. Recent recommendations of a number of expert committees are discussed.

Adipose Tissue↗

PubMed1988

The prediction of body composition in poultry by estimation in vivo of total body water with tritiated water and deuterium oxide.

1. Birds (n 169) which varied in age, live weight, nutritional history, physiological state and genotype were slaughtered and analysed for total body water. Before slaughter, birds were injected with the water isotopes tritiated water (TOH) or deuterium oxide (D2O), or both, to determine TOH space or D2O space, or both, as estimates of total body water in vivo. 2. At the mean total body water of all birds determined by desiccation, of 1096.4 (SD 424.1) g, TOH space and D2O space overestimated total body water by 10.4 and 8.5% respectively. The difference between the isotopes was significant (P less than 0.05). 3. Based on recovery of isotope it was postulated that the main reason for the observed overestimation of total body water in vivo was incomplete recovery of isotope due to the vacuum sublimation technique. The mean recovery (%) of added isotope to whole blood after vacuum sublimation was 93.0 (SD 2.6) and 92.4 (SD 5.5) of the theoretical concentrations of TOH and D2O respectively. 4. Nevertheless, accurate prediction of total body water was obtained from regression equations which included live weight and isotope-dilution space. Values required logarithmic (base 10) transformation before derivation of linear and multiple linear regression equations, and the precision of prediction was determined by the residual standard deviation (RSD). 5. Total body water could be predicted with nearly equal accuracy from live weight or isotope-dilution space (RSD 0.025 and 0.020 respectively). Prediction of carcass protein was more accurate from live weight (RSD 0.033) than from TOH space (RSD 0.036), and inclusion of both variables resulted in only a marginal decrease in RSD to 0.031. 6. The prediction of carcass fat and energy was markedly improved by the inclusion of isotope-dilution space in conjunction with live weight compared with live weight alone. 7. The relations show the developmental nature of body composition of domestic fowl given diets adequate in nutrients. The prediction equations demonstrate the precision possible for studies in which estimates of body composition in poultry are required without slaughter.

Animals↗

PubMed1988

Intraseason changes in the body composition of collegiate female gymnasts.

Body composition measures were collected pre-, mid- and post-season on a team of eight national-calibre collegiate women gymnasts to examine intraseason changes. Also analysed were interseason changes using pre- and post-season data on five of the eight subjects during the current and previous year, according to a 2 x 2 (years x tests) analysis of variance repeated-measures design. Skinfold, circumference and diameter measures were collected with percentage body fat, lean body mass and body density determined by regression equations developed specifically for collegiate female gymnasts. Intraseason body weight decreased significantly from pre- to mid-season (means = 55.0 and 53.6 kg respectively); but the difference between mid- and post-season (53.9 kg) values was not significant (P greater than 0.05). The majority of the 1.4 kg weight loss occurred during intense pre-season conditioning and not during the actual season. Percentage body fat, on the other hand, decreased significantly from pre- to mid-season and mid- to post-season (means = 21.4%, 17.4% and 13.45% respectively; P less than 0.0005). Body density increased significantly from pre- to mid-season and mid- to post-season (means = 1.0476, 1.0584 and 1.0681 respectively; P greater than 0.0005). Of the circumference and skinfold values used in calculating percentage body fat and body density, only the skinfold values displayed significant decreases throughout the season. Interseason analyses revealed no significant changes in any of the dependent measures between seasons, despite consistent trends. There were no significant years x tests interactions and all intraseason changes for two seasons (n = 5) were the same as those found in more detailed analysis of a single season (n = 8) except in the case of weight loss, which was marginally significant (P less than 0.046) in the single-season and not in the dual-season analysis (P greater than 0.05). Body composition of these gymnasts changed in many ways within competitive seasons. The most pronounced changes observed were decreases in subcutaneous fat and increases in body density. This study reinforces the need for administrators, coaches and athletes to be concerned with percentage body fat and skinfold measures rather than weight alone when determining if a person is 'fat'.

Adipose Tissue↗

PubMed1994

[Variations of body composition by bioelectric impedancemetry after major surgery].

Body water variations are traditionally measured postoperatively by fluid balance and body weight. Bioelectrical impedance assessment permits the evaluation of body composition, i.e., lean body mass, body fat and total body water. We compared the traditional method (body weight and fluid balance) with bioelectrical impedance assessment while estimating body water. Body weight, fluid balance, resistance, reactance, lean body mass, body fat, total body water, triceps skinfold and total protein blood level were measured prospectively (preop, and on days 1, 3 and 5 postop) in 30 patients admitted for major surgery (thoracic, abdominal or vascular). The results suggest that body composition changed significantly with time (p < .05); in all 3 surgical groups. There was a low correlation between total body water measured by bioelectrical Impedance and fluid balance. Bioelectrical impedance assessment is sensitive to body water changes but appears to overestimate these variations compared to the traditional method.

Blood Proteins↗

PubMed1997

Changes in fat-free mass and fat mass in postpartum women: a comparison of body composition models.

OBJECTIVES: (1) To compare 2-, 3- and 4-component models of body composition based on total body water (TBW), underwater weighing (UWW), skinfold thicknesses (SF), total body potassium (TBK), dual-energy X-ray absorptiometry (DXA) and total body electrical conductivity (TOBEC); (2) to compare postpartum changes in body composition estimated by the 2-, 3- and 4-component models and (3) to test for an effect of pregnancy or lactation on the hydration, density and potassium content of fat free mass (FFM) in postpartum women. DESIGN: Longitudinal measurements of body composition at 3, 6 and 12 months postpartum. SUBJECTS: Thirty-five healthy postpartum women, aged 30.2 +/- 3.5 y. MEASUREMENTS: Body composition was estimated by 2-component models based on TBW, UWW, SF, TBK, DXA or TOBEC; 3-component models based on TBW and UWW (Fuller 3, Siri 3); and a 4-component model (Fuller 4) based on TBW, UWW and bone mineral content. RESULTS: Systematic differences were seen among the various body composition models, with the following ranking from lowest to highest estimate of fat mass (FM): TOBEC, TBW, Fuller 3, Siri 3, Fuller 4, UWW, SF, TBK, and DXA. Estimated changes in FFM and FM were not significantly different among methods, except for the 3-6 months FFM and FM changes estimated from TBW, which differed from SF, DXA, and TOBEC. Pregnancy-induced changes in the hydration, density and potassium content of FFM were not evident by 3 months postpartum (0.73 +/- 0.02, 1.099 +/- 0.015 kg/l and 2.31 +/- 0.10 g/kg, respectively). CONCLUSION: In spite of systematic differences among body composition models for the measurement of FFM and FM, changes in FFM and FM did not differ significantly among the models. Since there was no apparent effect of pregnancy or lactation on the postpartum composition of FFM, 2-component models of body composition are acceptable for use in postpartum women beyond the puerperium.

Adult↗

PubMed1981

The effect of malnutrition on body composition.

The effect of malnutrition upon body composition was evaluated by determining body composition using multiple isotope dilution in 25 normal volunteers, in 75 patients with clinical malnutrition and in 20 patients who underwent an elective operative procedure of moderate severity. Malnutrition resulted in a loss of body cell mass, accompanied by an expansion of the extracellular mass. In the patients with clinically obvious malnutrition, the size of the body cell mass was reduced to 60 per cent normal, while the extracellular mass was 24 per cent more than normal. By the fifth day following an uncomplicated extensive operation, the body cell mass was reduced by 13.9 per cent, while the extracellular mass was increased by 9.6 per cent. The expansion of the extracellular mass obscures the loss of body cell mass, and therefore, weight loss does not accurately reflect the loss of cellular mass.

Body Composition↗

PubMed1979

Direct genetic and postnatal maternal genetic effects on body composition in mice selected for body weight.

Line crossfostering techniques were used to study differences among selected and control lines of mice in direct genetic and postnatal maternal genetic influences on preweaning (day 12) body weight and composition. The lines were selected for high (H6) and low (L6) 6-week body weight and the control line (C2) was maintained by random selection. There were positive correlated responses to selection in both direct genetic and postnatal maternal genetic effects on body weight and weights of all body components (P less than 0.01) except for water and ash weight in H6. The correlated responses in postnatal maternal genetic effects were of the same order of magnitude as those in direct genetic effects. Correlated responses were greater in L6 than in H6. Correlated responses in direct genetic effects were positive (P less than 0.01) for water percent in H6 and ether extract percent in L6, and negative (P less than 0.01) for water percent and lean percent in L6. Correlated responses in postnatal maternal genetic effects were positive for ether extract percent and negative for water percent (P less than 0.01). Correlated responses were far greater in L6 than in H6 and were greater for postnatal maternal genetic effects than for direct genetic effects. Analyses of covariance results indicated line differences in the relative growth rates of the body components.

Analysis of Variance↗

PubMed2005

Reliability in estimates of body composition of birds: oxygen-18 versus deuterium dilution.

Body composition in birds was evaluated indirectly by 18O and 2H dilution. Body composition was determined by whole-body chemical analysis of eight adult roosters (Gallus gallus). In vivo measurements of total body water (TBW) were carried out using doubly labeled water (2H2 18O). Estimated dilution spaces using both the plateau and intercept approaches were compared with the results obtained by carcass lyophilization. Both 18O and 2H slightly overestimated TBW compared with the results obtained by lyophilization, by 2.2%+/-1.9% and 5.7%+/-0.2%, respectively; both differences were statistically significant (P<0.01). The difference between these isotope estimations was significant (P<0.001). However, isotope dilution spaces and TBW were highly correlated. There was a strong inverse relationship between total body fat and TBW percentages (r2=0.98, P<0.0001). The relation between TBW and body protein was significant. Water content in lean body mass (72.8%) obtained in our study was very close to that reported in mammals, demonstrating no fundamental difference in tissue water content between birds and mammals. Estimated body fat and protein values from isotopic dilution did not significantly differ from values obtained by direct chemical analysis (P>0.05), except for body fat in the Pace and Rathbun approach (Table 3). Although estimation of TBW and body composition by isotope dilution is time consuming and expensive, deuterium offers a reliable and low-cost alternative compared with 18O. The advantage of in vivo estimation of TBW with isotopic dilution in combination with the regression approach is that it permits repeated measurements of body composition on the same birds under laboratory and free-living conditions.

Animals↗

PubMed1997

Effects of gender, ethnicity, body composition, and fat distribution on serum leptin concentrations in children.

The Ob protein leptin has been shown to be closely correlated with measures of body fat in humans and animals. Studies have suggested that there are both gender and ethnic differences in serum leptin concentrations, even after controlling for total and relative body fat and body mass index. We hypothesized that gender and ethnic differences in serum leptin concentrations are due to differences in both body composition and body fat distribution. We measured fasting serum leptin concentration, body composition (fat mass and fat-free mass by dual energy x-ray absorptiometry), and body fat distribution (intraabdominal and sc abdominal adipose tissue by computed tomography) in 74 prepubertal boys and girls (43 African-Americans and 31 Caucasians). Our results showed that gender differences in serum leptin concentrations could not be fully explained by differences in body mass index, total fat mass, or relative body composition. However, when serum leptin concentrations were adjusted for differences in relative body composition (fat mass and fat-free mass) and body fat distribution (sc and intraabdominal adipose tissue), gender no longer had an independent effect on the serum leptin concentration. Serum leptin concentrations were not influenced by ethnicity. Thus, when comparing group differences in serum leptin concentrations, it is necessary to adequately control for group differences in body composition and fat distribution.

Adipose Tissue↗

PubMed2000

Coronary risk profiles in men with coronary artery disease: effects of body composition, fat distribution, age and fitness.

BACKGROUND: Few studies have investigated the influence of body composition, abdominal obesity, age and fitness on coronary risk factors in populations of patients with coronary heart disease (CHD). We investigated whether abdominal obesity or generalized adiposity is a better predictor of cardiovascular risk in men with coronary artery disease (CAD), and the effects of exercise training on coronary risk factors in younger and older patients with CAD. METHODS: The study population consisted of 81 male patients aged 33-83 years (mean +/- SD 60.0 +/- 13.3 years) with established CAD. We studied the relationships among body composition, body fat distribution, dietary intake, peak aerobic capacity, lipid concentrations, and plasma glucose and insulin concentrations. We subsequently measured the influence of exercise training on these components. RESULTS: The study population was characterized by a high prevalence of obesity, particularly in younger patients. Body mass index, rather than body fat distribution, was the best anthropometric predictor of plasma triglyceride concentrations (r2 = 0.11, P < 0.05) and cholesterol/high-density lipoprotein cholesterol (HDL-C) ratio (r2 = 0.13, P < 0.01). Body weight, rather than body fat distribution, was the best predictor of plasma HDL-C concentration (r2 = 0.14, P < 0.01) and fasting glucose concentrations (r2 = 0.10, P < 0.05). Fat mass was the best anthropometric predictor of fasting plasma insulin concentrations (r2 = 0.38, P < 0.0001) and for the glucose-insulin ratio (r2 = 0.39, P < 0.0001) in men with CAD. Younger patients tended to have greater improvements in HDL-C concentrations and the cholesterol:HDL-C ratio than did older individuals, as a result of exercise training. CONCLUSION: In men with CAD, general measures of obesity, such as body weight, body mass index, and fat mass are better predictors of coronary risk factors than body fat distribution. Younger and older men with CAD experienced similar improvements in body composition and body fat distribution after an exercise training program.

Adult↗

PubMed1991

Effect of a very-low-calorie diet on body composition and resting metabolic rate in obese men and women.

Very-low-calorie diets (VLCDs) provide a rapid decrease in total body weight, but limited data are available regarding the extent of fat loss and whether body fat distribution is altered. The purpose of this study was to investigate body composition, body fat distribution, and resting metabolic rate in obese men and women and to compare bioelectrical impedance analysis (BIA) with hydrodensitometry before and after 12 weeks of treatment in a VLCD program. Body composition was assessed by hydrodensitometry and BIA. Circumference measures were used to determine waist:hip and waist:thigh ratios. Seventeen subjects lost a mean of 24.2 kg. A mean of 75.5% of the weight loss was adipose tissue as measured by hydrodensitometry. BIA underestimated body fat percentage compared with hydrodensitometry in this obese population. Waist:hip and waist:thigh ratios showed a small but significant decrease, implying a decreased risk for diabetes and cardiovascular disease after weight loss. Resting metabolic rate, as measured by oxygen consumption, dropped 23.8% during the 12 weeks of the VLCD. The findings indicate that a VLCD can provide a rapid weight loss of more than 75% fat and a concomitant decrease in waist:hip and waist:thigh ratios. The findings also indicate that BIA may not be a useful tool in assessing fat loss in obese subjects. Finally, it appears that the decrease in resting metabolic rate that occurs during treatment with VLCD does not correlate with changes in lean body mass.

Adipose Tissue↗

PubMed1997

Relative validity of clinical techniques for measuring the body composition of persons with amyotrophic lateral sclerosis.

Tracking body composition is necessary to understand how amyotrophic lateral sclerosis (ALS) is affecting a patient's morphology and to provide a basis for appropriate nutritional advice throughout disease progression. Dual X-ray absorptiometry (DEXA) has been shown to reliably detect body composition changes in persons with ALS. However, this procedure is expensive and available primarily for research. The purpose of this study was to determine the relative validity of two common clinical techniques, anthropometry and bioelectrical impedance analysis (BIA), for measuring the body composition of persons with ALS. Twenty-three persons with ALS volunteered for the study; seven with primarily bulbar symptoms, five with primarily arm weakness, five with primarily leg weakness, and six with significant weakness in all extremities. On a single day subjects underwent body composition analysis by the three techniques, with DEXA serving as the criterion method. Anthropometry and BIA results were converted to lean and fat mass using eight prediction equations commonly cited in the literature. Anthropometry measures were also converted to estimates of muscle mass using two additional equations. Both BIA and anthropometry tended to overestimate lean mass and underestimate fat mass compared to DEXA. However, the BIA prediction equations had smaller mean differences, larger correlations, and smaller standard errors of estimate than the anthropometry equations. The Lukaski et al. BIA equation (Lukaski, H.C., Bolonchuk, W.W., Hall, C.B., Siders, W.A., 1986. Validation of tetrapolar bioelectrical impedance method to assess human body composition. J. Appl. Physiol. 60, 1327-1332) most closely matched the values derived by DEXA and is probably the best method for measuring the lean and fat mass of persons with ALS, as long as they maintain adequate hydration levels. The Heymsfield et al. equation (Heymsfield, S.B., McManus, C., Smith, J., Stevens, V., Nixon, D.W., 1982. Anthropometric measurement of muscle mass: revised equations for calculating bone-free arm muscle area. Am. J. Clin. Nutr. 36, 680-690) for estimating muscle mass may also be a useful clinical tool for this population. Further longitudinal studies are needed to determine whether the equations that correlated best with DEXA at a single point in time are also sensitive enough to detect changes in body composition over a period of time.

Absorptiometry, Photon↗

PubMed2000

Randomised controlled trial of postnatal sodium supplementation on body composition in 25 to 30 week gestational age infants.

AIMS: To compare the effects of early and delayed sodium supplementation on body composition and body water compartments during the first two weeks of postnatal life. METHODS: Preterm infants of 25-30 weeks' gestation were stratified and randomly assigned according to gender and gestational age, to receive a sodium intake of 4 mmol/kg/day beginning either on the second day after birth or when weight loss of 6% of birthweight had been achieved. Daily sodium intake, total fluid intake, energy intake, urine volume, and urinary sodium excretion were recorded. Total body water was measured by H(2)(18)O dilution on days 1, 7, and 14, and extracellular fluid volume by sodium bromide dilution on days 1 and 14. RESULTS: Twenty four infants received early, and 22 delayed, sodium supplementation. There were no significant differences between the groups in body water compartments on day 1. In the delayed group, but not the early group, there was a significant loss of total body water during the first week (delayed -44 ml/kg, p=0. 048; early 6 ml/kg, p=0.970). By day 14 the delayed, but not the early group, also had a significant reduction in extracellular fluid volume (delayed -53 ml/kg, p=0.01; early -37 ml/kg, p=0.2). These changes resulted in a significant alteration in body composition at the end of the first week (total body weight: delayed 791 ml/kg; early 849 ml/kg, p=0.013). By day 14 there were once again no significant differences in body composition between the two groups. CONCLUSIONS: Body composition after preterm birth is influenced by the timing of introduction of routine sodium supplements. Early sodium supplementation can delay the physiological loss of body water that is part of normal postnatal adaptation. This is likely to be of particular relevance to babies with respiratory distress syndrome. A tailored approach to clinical management, delaying the introduction of routine sodium supplements until there has been postnatal loss of body water, is recommended.

Body Composition↗

PubMed2001

The effect of chromium picolinate on muscular strength and body composition in women athletes.

Fifteen women softball athletes were randomly divided into 2 groups, the chromium treatment group (n = 8) and the placebo control group (n = 7) to examine the effect of chromium, in the form of chromium picolinate (CrPic) supplementation, on muscular strength, body composition (body weight, percent body fat, and lean body mass), and urinary excretion. The CrPic supplementation consisted of a 500 ug dosage taken once per day. All participants trained 3 times per week with 2-3 sets of 8-12 repetitions at 80% of 1 repetition maximum (1RM) using variable resistance machines and free weights. No significant (p < 0.05) differences in muscular strength or body composition were found after 6 weeks of resistance training. In addition, chromium excretion (microg per 24 every hours) was examined and increased significantly with the treatment group after the 6-week period.

Adolescent↗

PubMed2003

Chemical body composition of 20 Thoroughbred foals at 160 days of age, and preliminary investigation of techniques used to predict body fatness.

AIMS: To determine the chemical body composition of Thoroughbred foals born in two consecutive years, and to investigate several techniques used to predict body composition in foals born in the second year, with particular reference to fat. METHODS: The chemical composition of 20 foals at around 160 days of age, born in two years, was determined. In vivo techniques to predict body composition were assessed in 23 foals born in Year 2, before and after euthanasia; 10 of these foals were used for chemical body composition analysis. Techniques to assess body composition in vivo included liveweight (LW), overall and regional condition scores, ultrasonic fat thickness measurements over the ribs and rump, linear measurements and bioelectrical impedance analysis. Correlations were determined between ultrasonic fat thickness, and bioelectrical impedance analysis, before and after euthanasia. Stepwise regression analysis was used to determine the relationships between in vivo techniques used to assess body composition and the chemical body composition of 10 animals. RESULTS: Foals used for analysis of chemical composition weighed between 220.5 and 260.0 kg before euthanasia. Fat content ranged from 5.5-13.0% of the partial empty bodyweight (LW less head, gastrointestinal contents, distal limbs and skin). Fillies had significantly more fat mass and percentage fat than colts (p=0.031 for both measurements). The mean chemical composition of the fat-free partial empty body was 73.2% (SD 0.6) water, 22.7% (SD 0.9) protein, and 4.1% (SD 0.4) ash. Most of the variation in the concentration of empty body water was associated with variation in the concentration of fat (p<0.001). The live animal overall condition scores were correlated with fat mass and concentration (p=0.006 and p=0.013, respectively; n=10). Condition score over the rib region was highly correlated with fat mass and fat concentration (p=0.004 and p<0.001; n=10). Ultrasound measurements taken 10 cm cranial to the tailhead and 4 cm from midline, used to assess the thickness of rump fat, were correlated with condition score (p=0.001), and explained 71% of the variation in body fat mass (p=0.002; n=10).Nearly 50% of the variation in fat-free mass and partial empty body water mass were associated with variation in the impedance indices calculated from length and bioelectrical impedance analysis measurements (p=0.023 and p=0.026, respectively; n=10). CONCLUSIONS: At around 42% of expected mature weight, fillies were significantly more fat than colts. Condition scores were correlated with partial empty body fat mass, and there was a trend for higher scores in fillies compared to colts. Much of the variation in water or protein mass of the partial empty body could be explained by variations in LW. CLINICAL RELEVANCE: Measurements of LW, rump fat and condition score are useful predictors of the chemical composition of foals at 5 months of age.

Journal Article↗

PubMed1994

Implications of genetic changes in body composition on beef production systems.

Changing the body composition of beef has implications for the entire beef production system. The dynamic nature of an animal's body composition and the production system itself make predictions of the implications of genetic change in body composition difficult. The cow-calf, stocker, and feeder segments of the production system will be affected differently. Leaner cattle tend to be slaughtered at heavier weights. Heavier weights effectively reduce composition differences of slaughter beef to less than the genetic differences. The effects of four pricing scenarios on slaughter weight and composition were evaluated for two leaner genotypes, one with no change in marbling and one with reduced marbling. A genetic difference of 1.0 yield grade at the same carcass weight resulted in slaughter beef that differed by .4 to 1.0 yield grade because of increased slaughter weights. Separate analyses suggested the stocker segment of beef production will be least affected by changes in body composition. Genotypes that are best fitted to slaughter requirements will have the most flexibility in types of stocker systems that can be used. The cow-calf segment of beef production has several options to adapt to leaner cattle. Management to reduce nutritional stress on leaner cows may be required by some producers. Increased selection for reproductive traits in cow genotypes may be needed. An alternative to selection for reproduction is terminal crossing to partially disassociate the slaughter animals' genotype from the cow's genotype.

Animal Husbandry↗