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Biomedical subjects

H R Cross

Publications and source records attributed to H R Cross.

At least 37 records · Page 2Linked to original sources
PubMed1993

Comparison of the fatty acid composition of subcutaneous adipose tissue from mature Brahman and Hereford cows.

The fatty acid composition of adipose tissue was measured in 37 mature Brahman and 32 mature Hereford cows to determine breed effect. Diet was held constant among all cows. When biopsied, cows were on oats and native cool-season annual pastures of good quality. Real-time ultrasound measurements of subcutaneous fat were taken at three locations (between the 12th and 13th rib, at the rump, and at the perianal region) to determine overall fatness. Overall fat thickness from these measurements was 1.3 cm for Brahman cows and 1.7 cm for Hereford cows (P < .01). Subcutaneous adipose tissue biopsy samples were collected from the perianal region, and fatty acid composition was determined using a gas chromatograph. Fatty acids were expressed in both normalized (area percentage) and gravimetric (grams/100 grams of fresh tissue) formats. In addition to greater overall subcutaneous fat thickness, Hereford cows contained 5 g more of fatty acids per 100 g of fresh adipose tissue than Brahman cows (P < .05). Subcutaneous adipose tissue from Hereford cows was higher (P < .01) in total saturated fatty acids and lower in mono- and polyunsaturated fatty acids than subcutaneous adipose tissue from Brahman cows. Compositional differences remained when breeds were compared by analysis of covariance at a common body fatness. The data suggest a genetic basis for the differences in fatty acid composition of Brahman and Hereford cows.

Adipose Tissue↗
PubMed1993

Effect of dietary fat and cholesterol level on tissue cholesterol concentrations of growing pigs selected for high or low serum cholesterol.

Thirty-six female pigs selected for three generations for high or low serum cholesterol were chosen to evaluate the effects of a high-fat, high-cholesterol diet and a low-fat, low-cholesterol diet provided on an ad libitum basis for 92 d beginning at 12 wk of age on the cholesterol content and percentage of fat in muscle and organ tissues. The pigs were four-way crosses (Chester White x Landrace x Large White x Yorkshire). Samples of cerebrum, heart, ileum, kidney, liver, longissimus muscle, semitendinosus muscle, and subcutaneous fat were collected from each animal for determination of cholesterol concentration. The liver was the only tissue that had a significant difference in cholesterol content and in fat percentage between the genetic groups (high serum cholesterol and low serum cholesterol) and between the two diets (high-fat, high-cholesterol diet and low-fat, low-cholesterol diet). There were no interactions between diet and genetic background on cholesterol accretion or on the percentage of fat in the tissues.

Adipose Tissue↗
PubMed1992

Esterification of fatty acids by bovine intramuscular and subcutaneous adipose tissues.

Exogenous fatty acid esterification in intramuscular and subcutaneous adipose tissues from 72-hr fasted or ad libitum fed Angus cattle was investigated. Intramuscular (interfascicular) and subcutaneous adipose tissue snips were obtained from the longissimus dorsi muscle and were incubated with radioisotopically labeled fatty acids (palmitate, stearate, oleate, linoleate or linolenate) at three different concentrations (0.3 mM, 0.6 mM and 2.0 mM) to assess rates of fatty acid incorporation into glycerolipids. Rates of fatty acid esterification in vitro increased with fatty acid concentration in both intramuscular and subcutaneous adipose tissues. For all of the fatty acids investigated, triglycerides were the predominant products (60-85%). Subcutaneous adipose tissue had larger adipocytes and more actively (P less than 0.05) esterified fatty acids, with the exception of palmitate, than intramuscular adipose tissue. The rate of palmitate esterification was not different between tissues, although intramuscular adipose tissue esterified a greater proportion (P less than 0.10) of palmitate as triglyceride (85%) than did subcutaneous adipose tissue (75%). Relative rates of incorporation of fatty acids into lipids in intramuscular and subcutaneous adipose tissues were: palmitate greater than linolenate greater than linoleate greater than stearate. In general, 72-hr fasting did not significantly reduce the rates of fatty acid incorporation in bovine adipose tissues. Results of this study revealed that:i) rates of exogenous fatty acid incorporation into adipose tissue lipids were dependent on the medium fatty acid concentration and adipose tissue depot; and ii) the relative esterification rates of the various fatty acids in vitro did not necessarily reflect the proportion of these fatty acids in bovine adipose tissues.

Adipose Tissue↗
PubMed1992

Effect of frame size, muscle score, and external fatness on live and carcass value of beef cattle.

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in slaughter frame size and muscle thickness score, as well as adjusted 12th rib fat thickness. After USDA carcass grade data collection, one side of each carcass was fabricated into boneless primals/subprimals and minor tissue components. Cuts were trimmed to 2.54, 1.27, and .64 cm of external fat, except for the bottom sirloin butt, tritip, and tenderloin, which were trimmed of all fat. Four-variable regression equations were used to predict the percentage (chilled carcass weight basis) yield of boneless subprimals at different fat trim levels (.64, 1.27, and 2.54 cm) as influenced by sex class, frame size, muscle score, and adjusted 12th rib fat thickness. Carcass component values, total carcass value, carcass value per 45.36 kg of carcass weight, and live value per 45.36 kg of live weight were calculated for each phenotypic group and external fat trim level. Carcass fatness and muscle score had the most influence on live and carcass value (per 45.36 kg weight basis). Carcasses with .75 and 1.50 cm of fat at the 12th rib were more valuable as the trim level changed from 2.54 cm to .64 cm; however, for carcasses with 2.25 cm of fat at the 12th rib, value was highest at the 2.54 cm trim level. Value was maximized when leaner cattle were closely trimmed. There was no economic incentive for trimming light-muscled or excessively fat carcasses to .64 cm of external fat.

Adipose Tissue↗
PubMed1992

The role of instrument grading in a beef value-based marketing system.

A functional value-based marketing system must have a means of identifying the value of individual animals or carcasses. The U.S. beef industry has had a strong interest in instrument grading for the past 11 yr. With the major shift toward a value-based system of trading (carcass), the beef industry has defined its needs for an instrument to assess value. Ultrasound seems to be the technology with the greatest chance of success. This paper outlines the history of instrument grading and industry's progress and plans in this area.

Animals↗
PubMed1992

Live and carcass values from different cattle types.

Slaughter steers and heifers (n = 345) were selected representing the following cattle types: English steers and heifers, Exotic steers and heifers, less than 50% Bos indicus steers and heifers, greater than or equal to 50% Bos indicus steers, and Holstein steers. Thirty sides representing 30 carcasses from each cattle type were fabricated into boneless subprimals and trimmed to three fat-trim levels: 2.54, 1.27, and .64 cm. Yields of cuts to each trim level were used to calculate values for each carcass component. Live values were calculated after slaughter and fabrication costs and drop credits were considered. Values were calculated for U.S. Choice and U.S. Select grades and the weighted average value accounting for the Choice/Select mix for each cattle type. At a constant quality level, fatter cattle types were more valuable at the 2.54 cm of fat-trim level. As fat was trimmed, the leaner cattle types became more valuable and the fatter types became less valuable. Cattle types with higher percentages of Choice carcasses were more valuable at the 2.54 cm of fat-trim level, but when subprimals were trimmed to .64 cm, the lower-grading carcasses became closer in value due to cutability advantages.

Adipose Tissue↗
PubMed1992

Yield grade and carcass weight effects on the cutability of lamb carcasses fabricated into innovative style subprimals.

Lamb carcass (n = 100) were selected from USDA yield grades (YG) 2, 3, and 4 and carcass weight (CW) groups 20.4 to 24.9, 25.0 to 29.5, and 29.6 to 34.0 kg. Lamb carcass were fabricated into semiboneless and boneless subprimals and trimmed to three s.c. fat trim levels: .64, .25, and .00 cm of fat remaining. Innovative subprimals were fabricated and yields were calculated for the subprimals and dissectible components (lean, bone, connective tissue, external fat, and seam fat) from each of the various subprimals. Carcass weight as a main effect in a two-way analysis of variance did not account for a significant amount of the variation in yield among trimmed subprimals or the percentage of the dissectible components, but USDA YG was a significant main effect in determining variation in yield for many of the subprimals or dissectible components. Muscle seaming of shoulders and legs and removal of excessive tails on the loin and rack resulted in a majority of the seam fat being removed from these cuts. Dissection data clearly showed that seam fat is a major component of rack and shoulder cuts and with increasing fatness or higher numerical yield grade there are clearly increased amounts of this depot. Increased trimming of external fat magnifies and draws more attention to the amount of seam fat remaining. Production of heavy, lean lambs would be more useful in an innovative type of program because of the larger-sized muscles. Heavy, fat lambs would not be as useful because of their decreased yields and excess seam fat located in cuts that cannot be muscled-seamed because of the loss of retail cut integrity. Seam fat was highly correlated to percentage of kidney and pelvic fat and to external fat thickness and with USDA yield grade but was not strongly correlated to carcass weight.

Adipose Tissue↗
PubMed1992

Development of a quantitative quality grading system for mature cow carcasses.

Data from 400 cow carcasses were used to develop a new quality grading system. First principal component (FPC) values were determined for shear force (SHR) and palatability attributes of tenderness, connective tissue amount, flavor, and juiciness (JUC). Associated eigenvector load values for those traits were -.48, .54, .51, .46, and .05, respectively, and FPC values ranged from -3.20 to 2.18. Linear regression, using FPC as the independent variate, and SHR and palatability attributes (8-point scale, where 8 was highest) as dependent variates explained a significant amount of variation (P less than .001) in all traits, except JUC, and resulted in R2 values of .71, .89, .80, .66, and .01, respectively. A predictive quality-grade equation was developed using FPC as the dependent variate, and overall maturity (OM), lean color, marbling score (MS), lean firmness, lean texture, fat color (FC), and marbling fineness ([marbling texture + marbling distribution]/2; 8-point scale, where 8 was highest) as independent variates. The resulting best-fit prediction equation (FPC = -.052-[.0031 x OM] + [.0013 x MS] + [.31 x FC]) explained a significant amount (P less than .001) of variation in FPC with R2 = .53, Cp = 15.0, and residual standard deviation = .69. A short-cut equation was developed from this prediction equation. Simple correlations for OM, MS, and FC with FPC were -.56, .39, and .64, respectively. Cow carcasses were assigned to one of three quality grades based on FPC values that corresponded with predetermined acceptability levels for each palatability trait. Newly developed grades were quantitative and less variable than existing grades. Future grades for cow carcasses should include fat color to predict palatability.

Adipose Tissue↗
PubMed1992

Development of a multivariate yield grade equation to predict compositional traits in mature cow carcasses.

Data from 68 cow carcasses were used to develop a new yield grading system. First principal component (FPC) values for compositional attributes (LNFT = separable lean weight/[lean+fat weight] x 100, LNBN = separable lean weight/[lean+bone+connective tissue weights] x 100, and BTPR = [defatted lean from the round, loin, rib, and chuck]/side weight x 100) were determined. The first component explained 83.5% of the standardized variance and load values were .63, -.52, and .58, respectively. The resulting FPC values ranged from -1.93 to 1.89. The linear regression of LNFT, LNBN, and BTPR (dependent variables) on FPC (independent variable) explained a significant amount of variation (P less than .001) in each case and resulted in R2-values of .98, .67, and .85, respectively. A best-fit yield grade equation, developed to predict FPC, included adjusted fat thickness (ADF), percentage of kidney, pelvic, and heart fat (KPH), and overall muscling grade (OM). The equation, FPC = 2.04 - (.67 x ADF) - (.21 x KPH) - (.0016 x OM), explained a significant amount (P less than .001) of variation in FPC with R2 = .94 and residual standard deviation = .25. Simple correlations for ADF, KPH, and OM with FPC were -.87, -.71, and -.80, respectively. Cow carcasses were assigned to one of three grades based on FPC values that corresponded with predetermined levels of LNFT, LNBN, and BTPR. These grades generally had smaller CV than existing grades. When used in conjunction with quality grades, proposed grades could be more useful to the cow meat industry.

Abattoirs↗
PubMed1992

Estimates of subprimal yields from beef carcasses as affected by USDA grades, subcutaneous fat trim level, and carcass sex class and type.

One hundred beef carcasses were selected to represent the mix of cattle slaughtered across the United States. Selection criteria included breed type (60% British/continental European, 20% Bos indicus, and 20% dairy carcasses), sex class (beef and Bos indicus: 67% steers, 33% heifers; dairy: 100% steers), USDA quality grade (4% Prime, 53% Choice, and 43% Select), USDA yield grade (10% YG 1, 43% YG 2, 40% YG 3, and 7% YG 4), and carcass weight (steers: 272.2 to 385.6 kg, heifers: 226.8 to 340.2 kg). One side of each carcass was fabricated into boneless subprimals and minor cuts following Institutional Meat Purchase Specifications. After fabrication, subprimals were trimmed progressively of fat in .64-cm increments beginning with a maximum of 2.54 cm and ending with .64 cm. Linear regression models were developed for each individual cut, including fabrication byproduct items (bone, fat trim) to estimate the percentage yield of those cuts reported by USDA Market News. Strip loin, top sirloin butt, and gooseneck rounds from heifers tended to have a higher percentage yield at the same USDA yield grade than the same cuts from steers, possibly resulting from increased fat deposition on heifers. Percentage of fat trimmed from dairy steers was 2 to 3% lower than that from other sex-class/carcass types; however, due to increased percentage of bone and less muscle, dairy steers were lower-yielding. Fat trimmed from carcasses ranged from 7.9 to 15.6% as the maximum trim level decreased from 2.54 to .64 cm.

Adipose Tissue↗
PubMed1992

Beef carcass composition of slaughter cattle differing in frame size, muscle score, and external fatness.

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in slaughter frame size and muscle thickness score, as well as carcass adjusted 12th-rib fat thickness. After collection of USDA carcass grade data, one side of each carcass was fabricated into boneless primals, subprimals, and minor tissue components. Cuts were trimmed to 2.54, 1.27, and .64 cm of external fat, except for the knuckle, tri-tip, and tenderloin, which were trimmed of all fat. Forced four-variable regression equations were used to predict the percentage (chilled carcass weight basis) yield of boneless subprimals at the three fat trim levels as influenced by sex class, frame size, muscle score, and adjusted 12th-rib fat thickness. Independent variables that had the most influence on percentage yield of primals and boneless subprimals were adjusted 12th-rib fat thickness and sex class. Within the same phenotypic group, percentage of trimmable fat increased by 2.32% as 12th-rib fat thickness increased by .75 cm. Estimated percentage yield of the major subprimals from the loin and round tended to be higher or relatively equal for heifer carcasses at all trim levels compared with those subprimals from steer carcasses. Holding frame size, sex class, and fat thickness constant, there was a higher percentage yield of chuck roll, rib eye roll, and strip loin for carcasses from thick-muscled cattle than for those from average- and thin-muscled cattle. Frame size had little effect on percentage yield of boneless subprimals.

Abattoirs↗
PubMed1992

Effect of dietary fat and cholesterol level on growing pigs selected for three generations for high or low serum cholesterol at age 56 days.

Thirty-six female pigs selected for three generations for high (HS, n = 18) and low (LS, n = 18) serum cholesterol at 56 d of age were used to test the hypothesis that the two populations would respond differently to a high-fat, high-cholesterol diet (HD) and a low-fat, low-cholesterol diet (LD). The animals were four-way crosses (Chester White x Landrace x Large White x Yorkshire). All pigs were fed a standard corn-soybean meal starter diet from weaning (at 4 wk) to 8 wk of age and a grower diet from 8 to 12 wk of age. Initial serum total cholesterol concentration at 12 wk of age was higher (P less than .05) in HS than in LS pigs (94.6 vs 76.9 mg/dL, respectively). The effect of genetic background persisted throughout the 13-wk experiment (25 wk of age); there was no interaction between diet and genetic background in serum total cholesterol (final concentrations were 114.3 mg/dL in HS-HD; 107.0 mg/dL in HS-LD; 105.9 mg/dL in LS-HD; and 89.7 mg/dL LS-LD). Trends over time revealed significant effects of diet (P less than .01) and genetic background (P less than .01) on serum total cholesterol. There was no effect of genetic background on high-density lipoprotein-cholesterol concentration; high-density lipoprotein-cholesterol as a percentage of serum total cholesterol was similar for all groups: 43% for HS-HD, 48% for HS-LD, 42% for LS-HD, and 45% for LS-LD.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Development and preparation of lean meat products.

When the effect of food on human lipoprotein levels is tested, or when human consumption of dietary lipids must be controlled or limited, all food needs to be provided under controlled conditions to achieve consistent composition and sensory traits. It is especially important to control the composition of foods, particularly fat and fatty acid content. Because of the inherent biologic variability in the chemical composition of animal tissues (beef in particular), raw materials must be selected carefully and prepared under strict guidelines. In addition, chemical composition should be verified initially and during the production of the product to ensure the accuracy necessary for controlled dietary intake. Furthermore, the meat provided must be easy for the study subject to prepare, be of consistent serving size, and yet be highly palatable to maintain the subject's interest and participation. This article outlines the protocol for developing lean meat products for use in nutrition studies in which fat content must be controlled, especially those studies designed to examine the effect of fat content on human lipoproteins. Preliminary studies, procurement of raw materials, procedures for recipe selection, product preparation, and sampling procedures for verification of chemical composition are described. Our findings indicate that fat intake from beef, chicken, and fish can be controlled for use in nutrition studies.

Animals↗
PubMed1991

Lipogenesis in acute and 48-hour cultures of bovine intramuscular and subcutaneous adipose tissue explants.

In this study, the interactions among breed of cattle, adipose tissue site and specific incubation conditions were investigated. Subcutaneous and i.m. adipose tissues were obtained from 10 Angus and 9 Santa Gertrudis steers immediately postmortem. Adipose tissue explants were incubated acutely for 2 h immediately at slaughter or after being cultured 48 h with or without 1 mU/ml insulin and 30 mg/ml bovine serum albumin; the incorporation of 14C-labeled acetate and glucose (5 mM, plus 5 mM unlabeled lactate) into lipid fractions was measured. AT the same chronological age, Angus steers had a more youthful lean maturity score, higher USDA marbling score and higher USDA quality grade (P less than .05) than did carcasses from Santa Gertrudis steers. The lower marbling score of the Santa Gertrudis steers was paralleled by smaller i.m. adipocytes (P less than .05) relative to Angus steers. Pentose cycle reductase and NADP-malate dehydrogenase activities were greater in Angus i.m. adipose tissue than in Santa Gertrudis i.m. adipose tissue, which would provide more reducing equivalents (NADPH) and glycerol for fatty acid biosynthesis and triacylglycerol esterification. Correspondingly, Angus i.m. adipose tissue exhibited a greater rate of lipogenesis from acetate and glucose (P less than .05) than did Santa Gertrudis i.m. adipose tissue in acute incubations. The presence of insulin resulted in higher rates of lipogenesis from acetate in Angus s.c. adipose tissue than in Santa Gertrudis s.c. adipose tissue after 48 h of explant culture. These data indicate that i.m. and s.c. adipose tissues exhibit aspects of lipid metabolism unique to each tissue and suggest that breed-related differences in adipose tissues may explain the divergent responses to insulin observed in different laboratories.

Adipose Tissue↗
PubMed1991

Relationships between pork loin palatability traits and physical characteristics of cooked chops.

Pork loins (n = 72) were selected so that marbling scores would range from "practically devoid" to "abundant" in the longissimus muscle. Loin chops were cooked and rated by a trained six-member sensory panel. Physical and chemical characteristics were stratified according to marbling level (divided into 10 subclasses), muscle structure, shear force, overall palatability, and juiciness (each divided into three subclasses). The highest ratings for overall palatability were assigned to chops with high reflectance (685 nm), low moisture (70.1%), high i.m. fat (9.1%; or, high marbling score), low protein (19.4%), and low cooking loss (25.9%). Chops with the highest percentage of cooking loss were high in moisture content (75.59%), low in i.m. fat (1.78%), and high in protein content (21.54%). Differences in muscle structure, shear force, overall palatability, and juiciness were associated with differences in percentages of protein, moisture (whole tissue basis [WTB]) and fat (WTB). Pork loins with marbling between "practically devoid-plus" and "small" had (P less than .05) more protein and less fat (WTB) than loins with marbling scores between "modest" and "abundant." Loins with overall palatability ratings between 4.0 and 6.0 had more moisture and protein (P less than .05) than did loins with palatability ratings of 6.1 to 8.0. Selecting pork loins with "small" or less marbling, extremely open structure, a juicy rating of "slightly juicy," and an overall palatability rating of "like slightly" would identify fresh loins that had lower fat and(or) higher protein content.

Animals↗
PubMed1991

National beef market basket survey.

Beef retail cases in supermarkets in 12 cities across the United States were surveyed for fat thickness measurements, cut representation, package weights and counts, and case space allocation. Randomly selected retail cuts were purchased and transported to Texas A&M University, where they were dissected into separable components. Samples of ground beef were obtained for chemical analysis. Over 42% of the beef retail cuts had no external fat, and approximately 75% of all cuts were boneless. The overall mean fat thickness for all retail cuts in the beef case was .31 cm, and the overall mean fat thickness for steaks and roasts from the major primals - chuck, rib, loin, and round - was .38 cm. The average percentage of separable lean was 79.0%, separable fat was 12.3%, and bone and connective tissue was 8.7%. Retail cuts had more than twice as much separable seam fat as separable external fat. Beef steaks and roasts had 27.4% less separable fat than values from USDA Agriculture Handbook 8-13. Of the ground beef surveyed, 37% was regular, 40% was lean, and over 22% was extra lean. Retail ground beef had approximately 10% less fat than values from USDA Agriculture Handbook 8-13.

Animals↗
PubMed1991

National beef tenderness survey.

To determine the average tenderness and sensory ratings of beef subprimal cuts sold in retail cases across the United States, retail cuts were purchased through typical retail outlets in 14 metropolitan cities and transported to Texas A&M University for sensory and Warner-Bratzler shear analysis. The overall mean shear force for all cuts was 3.65 kg, and the mean shear force values for chuck, rib, loin, and round cuts were 3.72, 3.36, 3.17, and 4.31 kg, respectively. No difference (P greater than .05) in tenderness was detected among the cuts from the rib. Mean palatability ratings and shear force values of top loin steaks were similar to those of rib cuts. Top sirloin steaks were tougher (P less than .05) and received the lowest sensory ratings compared with other loin cuts. Approximately two to three times as many round and chuck steaks had shear force values in excess of 4.6 kg compared with their roast counterparts. In all cases, roasts tended to be more tender than steaks from the same subprimal source. USDA Choice chuck retail cuts, compared to Select and No-roll chuck cuts, had approximately 10% fewer cuts with shear force values in excess of 4.0 kg. More work is needed to improve meat tenderness, primarily for retail cuts from the round and chuck primals. Future research must investigate the interaction of antemortem and postmortem factors associated with variation in beef tenderness.

Animals↗