Effects of conventional and grass-feeding systems on the nutrient composition of beef.

The objectives of this study were to determine the nutrient composition of grass-fed beef in the United States for inclusion in the USDA National Nutrient Database for Standard Reference, and to compare the fatty acid composition of grass-fed and conventionally fed (control) beef. Ground beef (GB) and strip steaks (SS) were collected on 3 separate occasions from 15 grass-fed beef producers that represented 13 different states, whereas control beef samples were collected from 3 regions (Ohio, South Dakota, and Texas) of the United States on 3 separate occasions. Concentrations of minerals, choline, vitamin B(12), and thiamine were determined for grass-fed beef samples. Grass-fed GB samples had less Mg, P, and K (P < 0.05), and more Na, Zn, and vitamin B(12) (P < 0.05) than SS samples. Fat color, marbling, and pH were assessed for grass-fed and control SS. Subjective evaluation of the SS indicated that grass-fed beef had fat that was more yellow in color than control beef. Percentages of total fat, total cholesterol, and fatty acids along with trans fatty acids and CLA were determined for grass-fed and control SS and GB. Grass-fed SS had less total fat than control SS (P = 0.001), but both grass-fed and control SS were considered lean, because their total fat content was 4.3% or less. For both GB and SS, grass-fed beef had significantly less (P = 0.001 and P = 0.023, respectively) content of MUFA and a greater content of SFA, n-3 fatty acids, CLA, and trans-vaccenic acid than did the control samples. Concentrations of PUFA, trans fatty acids, n-6 fatty acids, and cholesterol did not differ between grass-fed and control ground beef. Trans-vaccenic acid (trans-11 18:1) made up the greatest concentration of the total trans fats in grass-fed beef, whereas CLA accounted for approximately 15% of the total trans fats. Although the fatty acid composition of grass-fed and conventionally fed beef was different, conclusions on the possible effects of these differences on human health cannot be made without further investigation.

Primary cultures of stromal-vascular cells from pig adipose tissue: the influence of glucocorticoids and insulin as inducers of adipocyte differentiation.

Porcine stromal-vascular (S-V) cells from perirenal and subcutaneous fat depots were studied in a primary culture system. The ability of S-V cells to differentiate into adipocytes in response to insulin and to glucocorticoid treatments was determined. Treatments were either hydrocortisone plus insulin, dexamethasone plus isobutylmethylxanthine, or insulin. Insulin did not affect glycerol phosphate dehydrogenase (GPDH) activity or cytodifferentiation in porcine S-V cultures. All cultures differentiated in response to glucocorticoid addition. Glycerol phosphate dehydrogenase specific activity increased an average of 42.5% and the number of cell clusters with multilocular fat cells markedly increased. Cells receiving insulin after dexamethasone-stimulated differentiation had no greater ability to respond to the insulin than cells from control cultures. Glucocorticoids promoted cytodifferentiation of porcine S-V cells to adipocytes in a qualitative manner similar to other preadipocyte models; quantitatively, however, the response was greatly diminished.

Differentiation of adipose tissue and muscle in hypophysectomized pig fetuses.

In the present study, fetuses were hypophysectomized (hypox) in utero on d 72 to 74 of gestation with an electrical cauterizing needle. One to six successfully hypox fetuses were removed on d 110 of gestation from each of five gilts. Subcutaneous adipose tissue samples and semitendinosus muscles were obtained from the hypox fetuses and an equal number of control fetuses. Body weights of control fetuses (n = 15; mean +/- SE, 1,195 +/- 33 g) were similar to weights of hypox fetuses (n = 15; 1,179 +/- 67 g). Fat cell size in the middle subcutaneous layer of adipose tissue was increased in hypox fetuses (P less than .01) compared with control fetuses. The number of obvious fat cell clusters (outer layer) in lipid stained sections was reduced (P less than .01) by 50% in hypox fetuses. Histochemical reactions for glucose-6-phosphate dehydrogenase, esterase and lipoprotein lipase (LPL) activities in middle layer cell clusters were considerably enhanced in sections from hypox fetuses compared with sections from controls. Quantitative analysis of percent light transmittance (Zeiss photometer) through LPL-stained cell clusters indicated an increase (P less than .001) in LPL staining in sections from hypox fetuses when compared with sections from control fetuses. Transverse muscle sections (cryostat) from hypox fetuses failed to show normal patterns (as seen in control muscles) of reactions for acid ATPase, malate dehydrogenase (NAD-dependent), NADH-TR and alpha-glycerol phosphate dehydrogenase (without NAD). The number of muscle fibers that were stained for these enzymes was greatly reduced in hypox fetuses compared with control fetuses. The number of lipid positive fibers was also reduced in hypox fetuses compared with control fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of urea dilution as a technique for estimating body composition of beef steers in vivo: validation of published equations and comparison with chemical composition.

Urea dilution equations for prediction of empty body water in live cattle, developed by three separate groups of investigators, were evaluated by comparing empty body water calculated by these equations with that measured chemically in 6-, 12- and 18-mo-old crossbred beef steers (n = 10, 9 and 9, respectively). Of four equations for prediction of percent empty body water, one derived from mixed-breeds of steers overestimated empty body water in the 6-mo-old steers by 7.59% (P less than .05). For the 12- and 18-mo-old steers, calculated and measured percent empty body water did not differ (P greater than .05). Of seven equations for calculation of empty body water volume, two derived from Angus steers with an without live weight in the equation, and one derived from a combination of Angus and mixed-breeds of steers overestimated empty body water (P less than .05) in the 6-mo-old steers. No differences (P greater than .05) between calculated and measured empty body water volume were observed for either the 12- or 18-mo-old steers. When calculated empty body water values were regressed against that measured directly, all regression slopes were not different from 1 (P greater than .05). Intercepts from regressions involving percent empty body water (four equations) were not different from 0. Three of the seven equations for calculation of empty body water volume, one derived from bulls and the others from Angus steers had intercept estimates not different (P greater than .05) from 0. Validity required that these regressions have slopes not different from 1 and intercepts not different from 0. Empty body water calculated from equations that combined live weight and urea space were more highly correlated with directly measured empty body water than that calculated from equations derived only from urea space. Urea space correlations with body composition of our steers also were improved when live weight was included with urea space in multiple regression models. Results of this study suggest that before using any prediction equation for calculating body composition of cattle in vivo, equations should be tested with a sub-sample of cattle from the population for which its use is intended.

Evaluation of the use of deuterium oxide dilution techniques for determination of body composition of beef steers.

Body composition as estimated by a one- or two-compartment deuterium oxide dilution technique was compared with directly measured body composition of 15 large- and 15 small-frame steers. Body composition of the steers was measured at 219, 412 and 603 kg live weight. Empty body protein was overestimated (P less than .05) 3.6% from a one-compartment model (1 CM, using the slope, intercept method), while empty body protein was underestimated (P less than .05) 5.4% from a two-compartment kinetic model (2CM). Empty body ether extract estimated by 1 CM was not significantly different from the direct method, although 4.7% larger. Empty body ether extract was overestimated (P less than .001) 32.2% by the 2CM. Empty body water was accurately estimated from the 1CM when a 3.2% correction factor was used for the overestimation of total body water by the 1CM, but water in gastrointestinal tract contents was overestimated (P less than .001) 13.4% by the 1CM. Empty body water was underestimated (P less than .001) 7.8% by the 2CM, and water in gastrointestinal tract contents was overestimated (P less than .001) 41.8% by the 2CM due to its dependence on regression equations that differ between groups of cattle. The 2CM offered no advantage over the 1CM. A three-compartment model was not better than the 2CM in estimating body water compartments. Assuming the amount of empty body water associated with either empty body protein or ash to be constant seemed to be valid. Suggested values calculated from data presented in the literature for growing cattle with an empty body weight greater than 175 kg are .302 and .0668, respectively, for the ratios of protein and ash to water. The relationship between empty body fat and water was, percentage empty body fat = 94.27--(1.267)(percentage empty body water), which had a 1.25 residual standard deviation and a .98 coefficient of determination.

Muscle protein synthesis and growth of two strains of chicks vaccinated for Newcastle disease and infectious bronchitis.

Rates of in vitro protein synthesis were monitored during an 8-week period in male broilers and Leghorns. The birds received vaccinations during Weeks 2 and 5 posthatching for Newcastle disease and infectious bronchitis by the administration of a standard dose of the mixed vaccine in the drinking water. Both types of birds exhibited a marked decline in the rate of protein synthesis during each week after vaccination. The decline in ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) levels were not as pronounced as those for protein synthesis, but DNA concentrations did tend to reflect the protein pattern between Weeks 5 and 6. Live weight of both types of birds increased at a steady rate throughout the period, but grams of carcass protein accrued per week followed the protein synthesis rate patterns during the 8-week period. The results suggest that Leghorns are more susceptible than broilers to the stress of vaccination.

Growth and in vitro protein synthesis in two strains of chicks.

An in vitro method was used to estimate rates of skeletal muscle protein synthesis and degradation in fast (broiler) and slow (White Leghorn) growing birds. Four birds/strain were sacrificed at weekly intervals for 8 wk and biweekly thereafter to wk 14. The extensor digitalis communis, a muscle containing both red and white type fibers and the extensor carpi ulnaris, a white fiber-type muscle, were removed from the right wing and incubated in a Krebs-Ringer solution that contained either 14C-tyrosine for determination of rates of protein synthesis or cycloheximide for determination of rates of protein degradation. The contralateral muscles were removed and muscle weight, length and volume recorded. Proximate analysis was conducted on the carcass and inedible portions of the birds to determine protein, fat and moisture content. Nucleic acid concentrations were measured in the wing muscles. Broilers grew more rapidly than Leghorns, with a twofold difference in body weight by wk 3 and a threefold difference by wk 8. The greater total protein deposition, with more of this protein deposited in the carcass portion than the inedible portion. White muscle had a greater growth rate than the mixed fiber type muscle. Concentrations of RNA and DNA were similar between strains.