Higher Marbling Scores Research Articles

Performance and carcass traits of early-weaned steers receiving either a pasture growing period or a finishing diet at weaning.

A 2-yr study was conducted to evaluate 1) steers fed ad libitum high concentrate after weaning (CONC), or 2) steers grown on pasture for 82 d, followed by high-concentrate finishing (PAST), on the performance and carcass traits of 74 early-weaned (117 d of age) steers. Potential breed differences were evaluated using crossbred steers of three types: 1) 3/4 Angus x 1/4 Simmental (BRI), 2) 3/4 Simmental x 1/4 Angus (CON), and 3) 1/2 Wagyu x 1/4 Angus x 1/4 Simmental (WAG). Steers were randomly assigned within breed to the two treatments. There was no interactions (P > .10), so the data were pooled over years. The CONC steers had an ADG that was .17 kg/d higher (P = .0001), intake 1.09 kg/d lower (P = .0001), and gain:feed ratio .013 unit better (.190 vs .177, P = .008) than PAST steers overall. Growing treatment did not affect total concentrate consumed (P = .97). The BRI steers required 31 d less than did CON steers (P = .008), and 23 d less than WAG steers (P = .05) when fed to a constant fat end point (1.1 cm). The BRI steers exhibited an ADG .16 kg/d higher (P = .0003), tended (P = .07) to have an ADG intake .49 kg/d higher, and exhibited gain:feed .01 unit better (.189 vs 180) than WAG steers. When compared with CON steers, BRI steers consumed 310 kg less total concentrate (P = .0003). No differences (P > .38) were observed between growing treatments for carcass characteristics or sensory attributes except that CONC steers tended (P = .11) to improve percentage of steers grading Average Choice or higher by 47% over PAST steers. The WAG steers had a 76-unit higher marbling score (1,000 = Small00, 1,100 = Modest00) (P = .006) than BRI steers, resulting in 19% more (P = .09) steers grading > or = Choice and 82% more (P = .03) grading > or = Average Choice. Liver (P = .15) and rumen (P = .01) weights as a percentage of hot carcass weight were reduced for CONC steers. The CONC steers had higher gain, lower intake, better efficiency, reduced liver and rumen weights, and consumed the same amount of total concentrate when compared with PAST steers. The BRI steers had less finishing days and lower daily intake compared with CON steers. The WAG steers had more days finishing, lower gain, lower intake, more undesirable efficiencies, consumed the same amount of total concentrate, and improved quality grades compared with BRI steers.

Effects of breed and sire on carcass characteristics and fatty acid profiles of crossbred wagyu and angus steers

In a two-year experiment, 54 steers sired by seven Wagyu bulls [American Wagyu Association (AWA) sire numbers 331, 384, 388, 411, 429, 433 and 488] and 15 steers sired by two Angus bulls, all out of Angus-Hereford cows, were used to evaluate the effects of sire and breed on carcass characteristics and fatty acid composition. Steers were given ad-libitum access to a high-concentrate diet (15 % alfalfa cubes and 85 % barley supplement) for at least 170 days. Breed and individual sire effects were analysed. Wagyu-sired steers had higher marbling, maturity and quality scores, more estimated kidney, pelvic and heart fat, larger longissimus dorsi muscle areas, lower fat thicknesses and yield grades than Angus-sired steers ( p < 0.05). Steers sired by 388, 411 and 433 had lower fat thicknesses than steers sired by Angus, 429 and 488 ( p < 0.05). Steers sired by 384 and 388 had higher marbling scores per cm subcutaneous fat than steers sired by Angus, 429 and 488, and lower fat thickness per 100 kg of carcass weight than Angus-sired steers ( p < 0.05). For both subcutaneous fat and longissimus dorsi muscle, Wagyu-sired steers had higher ( p < 0.05) percentages of 14:0, 14:1, 16:0, 16:1, and lower percentages of 18:0 than Angus-sired steers. The genetic differences in carcass characteristics among Wagyu sires may enable us to select for improved marbling with less fat in the Wagyu breed. Some statistically significant ( p < 0.05) but small differences existed in fatty acid profiles between breeds and among sires.

Breed effects, dietary energy density effects, and retained heterosis on different measures of gain efficiency in beef cattle.

Retained heterosis for different measures of gain efficiency was estimated in F3 generation castrate male progeny in three composite populations finished on two levels of dietary energy density (2.82 and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Gain efficiency was evaluated in time constant (0 to 207 d), gain constant (310 to 540 kg), carcass weight constant (333 kg), and retail product weight constant (225 and 210 kg) end points and to different marbling score and longissimus muscle fat end points. Expressions of gain efficiency included live weight gain/megacalories of ME and retail product weight/megacalories of ME. Significant differences were observed among breeds in all measures of gain efficiency. Breeds that had the smallest weight to maintain tended to be more efficient in live weight gain in the time constant period, whereas breeds with the highest rate of gain tended to be more efficient in the gain constant period. To marbling score or longissimus muscle fat end points, breeds with the lowest marbling scores and smallest percentage fat in the longissimus muscle on an age constant basis (e.g., Limousin and Gelbvieh) tended to be less efficient, whereas breeds with the highest marbling score and highest percentage of fat in the longissimus muscle on an age constant basis (e.g., Hereford and Angus) tended to be more efficient. Breeds with the highest percentage of retail product (Limousin and Gelbvieh) were more efficient to retail product weight end points, or when retail product weight was the measure of output. Steers fed the higher energy density diet were more efficient in live weight gain to time constant, live weight gain constant, marbling score constant, and longissimus fat constant end points and were more efficient in the production of retail product weight to retail product weight end points because of the shorter period of maintenance. Retained heterosis was not consistent among composites in different measures of gain efficiency. Higher initial weights resulting in greater requirements for maintenance had a negative effect in composites for most measures of gain efficiency.

The effects of fat thickness and degree of marbling on pork colour and structure

Fat thickness (3rd–4th last rib) was weakly correlated with subjective pork structure score (R2 = 1.0%) and marbling score (R2 = 1.6%) in 399 boneless pork backs sampled from commercial processing plants. Pork colour and structure scores (R2 = 5.9 and 11.1%) were more highly correlated with marbling score than carcass fat and muscle depths (R2 = &lt; 2.0%). Pork backs that had structure scores of 1 and 2 (extreme to slight soft and exudative pork) tended to have low amounts of marbling (traces or less). A second trial with 311 pork backs also indicated that higher marbling scores were associated with lower frequencies of pale, soft and exudative pork. Key words: Pork quality, marbling, PSE

Effect of prepubertal body weight gain and breed on carcass composition at puberty in beef heifers

Fourteen prepubertal Angus heifers, all of which reached puberty, and 11 Santa Gertrudis (SG) heifers, eight of which reached puberty, were divided into two treatment groups. There was no breed difference in age at puberty for those that reached puberty. Treatment 1 (T1) heifers, fed to gain .5 kg/d, tended (P < .11) to be older than Treatment 2 (T2) heifers, fed to gain 1 kg/d, at puberty. Body weight and height were greater (P < .01) in SG than in Angus heifers at puberty. Angus heifers in T2 deposited more fat over the rump during the 15 wk before puberty, whereas T1 SG heifers deposited the least amount of fat (P < .05). Heifers in T2 were heavier at puberty (P < .05), had faster growing longissimus muscle areas (P < .05), and deposited more fat over the rib (P < .01) as they approached puberty. The T2 (P < .05) and Angus (P < .05) rib sections had more dissectible subcutaneous fat than did T1 and SG rib sections. Angus heifers had higher marbling scores (P < .05), as well as higher total lipid percentages for seam fat (P < .05), longissimus muscle (P < .01), other lean tissue (P < .05), and subcutaneous fat (P < .01). Predicted total lipid content for the edible portion of the dressed carcass was higher for T2 heifers (P < .09).

Importance of interindividual differences in quantitative descriptive psychophysics

Bulls (n = 115) of four slaughter ages (9, 12, 15 or 18 months) and of 15 genotypes were studied. In this analysis, each bullock was assigned to one of four breed groups—British and British crosses, Brahman and Brahman crosses. Jersey and Jersey crosses or Holstein and Holstein crosses. Slaughter age had an (P < 0·01) effect on marbling score, longissimus muscle area, fat thickness and yield grade while breed group had an (P < 0·01) effect on marbling score and quality grade. In general, British and British cross bullocks produced carcasses with the thickest subcutaneous fat, the highest marbling score and the highest USDA quality grade while Jersey and Jersey cross bullocks yielded carcasses with the lowest weight, smallest longissimus muscle area and the lowest USDA quality grade of the four breed-type groups. Increases in chronological age (from 9 to 18 months) were generally associated with a decrease in USDA maturity score, and increases in marbling score, USDA quality grade, longissimus muscle area, subcutaneous fat thickness and USDA yield grade. Shear force values decreased as bulls matured from 9 to 18 months of age. The meat from Brahman-type bulls had higher shear force values (P < 0·01) than that from bulls of the other breed groups. Steaks from British-type carcasses received the highest numerical ratings for sustained juiciness and flavor while steaks from the Brahman-type carcasses were assigned the lowest numerical ratings for juiciness. Breed-type had a greater effect on tenderness of bull beef than did chronological age.

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.

Factors influencing intermuscular fat and other measures of beef chuck composition

Carcasses from 59 steers produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls mated to Angus cows were used in this study. Effects of sire breed and feeding calves vs yearlings on fat depots in the chuck, when steers were fed to 1.0 cm external fat, were determined. Breed of sire and feeding calves vs yearlings had no effect (P greater than .05) on percentage of intermuscular fat. However, carcasses from Braford-sired steers had a higher (P less than .05) percentage of dissectable subcutaneous fat on the chuck than did those from other breed groups. Carcasses from Simmental-sired steers were superior (P less than .05) to those from Braford-sired steers in USDA yield grade and had a higher average marbling score (P less than .05) than the Simbrah-sired group. Estimated kidney, pelvic, and heart (KPH) fat was higher (P less than .05) in carcasses from Brahman-, Simbrah-, and Senepol-sired steers than in Braford-sired steers. Steers fed as calves had higher percentages (P less than .05) of KPH fat and major chuck muscles than did those fed as yearlings. The best single predictor of percentage of intermuscular fat within the chuck was adjusted fat over the ribeye (R2 = .46).

INFLUENCE OF STEAK TEMPERATURE AT THE BEGINNING OF BROILING ON PALATABILITY, SHEAR AND COOKING PROPERTIES OF BEEF LOIN STEAKS DIFFERING IN MARBLING

Beef loins representing six USDA marbling degrees provided steaks that were subjected to two thawing procedures prior to broiling at 70°C and subsequent evaluation of sensory, shear, and cooking properties. Loins from 120 carcasses were selected from the following six marbling degrees (20 loins/group): Moderately Abundant, Slightly Abundant, Moderate, Modest, Small, Slight. The two thawing procedures provided steaks of two internal temperatures before broiling (high = 10.5°C, low = 4.1°C). Reductions in marbling produced lower tenderness and juiciness ratings regardless of internal temperature prior to broiling. High initial-temperature produced higher tenderness and juiciness scores, less cooking loss, shorter cooking times and a more rare degree of doneness than the low initial-temperature. High initial-temperature resulted in instrumental measures more indicative of tenderness than low temperature, but only for steaks of Small and Slight marbling. However, high temperature produced lower beef flavor intensity in steaks from the higher marbling scores than low temperature. Use of higher internal meat temperatures just before broiling can reduce cooking time while enhancing tenderness and juiciness. With more highly marbled steaks, some additional broiling time may be necessary to develop beef flavor if higher internal meat temperatures were employed prior to broiling. Thawing procedures should be carefully controlled to prevent temperature abuse if it is decided to elevate meat temperatures prior to broiling.

Evaluation of performance characteristics in a diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. II. Carcass traits.

Evaluations of steer and heifer progeny from a diallel mating design of Simmental, Limousin, Polled Hereford and Brahman beef cattle over 5 yr are presented. Traits evaluated included final weight, hot carcass weight, ribeye area, 12th rib fat thickness, marbling score, yield grade, dressing percentage and percentage of kidney, pelvic and heart fat. Progeny of Simmental sires were heavier at slaughter than those with Brahman sires (P less than .05), but no differences were found for carcass weight. Dressing percentage was higher for Limousin crosses compared with progeny of other sire breeds (P less than .05). Similar results were found for dam breeds, except that progeny of Limousin dams had heavier carcasses with a higher dressing percentage (P less than .05) than Brahman crosses. Crosses of Limousin and Simmental had larger ribeye areas (P less than .05) compared with calves of the other breeds. Progeny of Polled Hereford dams had higher marbling scores and were fatter than progeny of dams of other breeds (P less than .05). Heterosis estimates were significant for all Brahman crosses for final weight, carcass weight and ribeye area, but these contrasts were negligible for other traits. Estimates of general combining ability were positive and significant for Simmental for final weight, carcass weight, ribeye area and marbling score and were significant and negative for Limousin for final weight, fat thickness and yield grade. Maternal values were generally small.

Effects of Compudose® implants from birth to slaughter on carcass and meat traits of young bulls and steers (1986)

Implanting young bulls with Compudose® three times from birth to slaughter resulted in performance similar to that of nonimplanted bulls, but decreased masculinity development. Implanted bulls tended to have higher marbling scores, more tender meat, more youthful carcasses, and lighter lean color than nonimplanted bulls. Although both implanted and nonimplanted bulls were more efficient and gained faster in the feedlot than implanted steers, the steers showed very little carcass masculinity and had finer-textured lean. Implanted steers had more youthful carcasses and lower Warner-Bratzler shear values than nonimplanted bulls. However, nonimplanted bulls grew faster, were more efficient, had larger ribeyes and lower yield grade numbers than implanted steers. For large-framed cattle, castration and implanting with Compudose® near birth result in the most desirable combination of performance, carcass, and meat quality traits.

Chronological age and breed-type effects on carcass characteristics and palatability of bull beef

Bulls (n = 115) of four slaughter ages (9, 12, 15 or 18 months) and of 15 genotypes were studied. In this analysis, each bullock was assigned to one of four breed groups—British and British crosses, Brahman and Brahman crosses. Jersey and Jersey crosses or Holstein and Holstein crosses. Slaughter age had an (P < 0·01) effect on marbling score, longissimus muscle area, fat thickness and yield grade while breed group had an (P < 0·01) effect on marbling score and quality grade. In general, British and British cross bullocks produced carcasses with the thickest subcutaneous fat, the highest marbling score and the highest USDA quality grade while Jersey and Jersey cross bullocks yielded carcasses with the lowest weight, smallest longissimus muscle area and the lowest USDA quality grade of the four breed-type groups. Increases in chronological age (from 9 to 18 months) were generally associated with a decrease in USDA maturity score, and increases in marbling score, USDA quality grade, longissimus muscle area, subcutaneous fat thickness and USDA yield grade. Shear force values decreased as bulls matured from 9 to 18 months of age. The meat from Brahman-type bulls had higher shear force values (P < 0·01) than that from bulls of the other breed groups. Steaks from British-type carcasses received the highest numerical ratings for sustained juiciness and flavor while steaks from the Brahman-type carcasses were assigned the lowest numerical ratings for juiciness. Breed-type had a greater effect on tenderness of bull beef than did chronological age.

CARCASS QUALITY CHARACTERISTICS OF THREE-WAY CROSS BEEF CATTLE REARED AT TWO LOCATIONS

Carcass quality characteristics of 3673 steers (M) and heifers (F) born over a 6-yr period (1973–1978) at Brandon, Manitoba (farm conditions) and Manyberries, Alberta (range conditions) were compared. The progeny produced were out of 10 specific F1 crosses of dams mated to bulls of the Charolais (C), Simmental (S), Limousin (L) and Chianina (Chi) breeds. Dam crosses included Hereford × Angus (HA) and crosses sired by C, S and L out of H, A and Shorthorn (N) dams. Calves weaned at Manyberries were fed and evaluated at Lacombe. Sex differences, at both locations, indicated F&gt;M for Warner-Bratzler shear force. At Brandon, M&gt;F for conformation score, F&gt;M for firmness score and F&gt;M for percentage protein. For Lacombe data, M&gt;F for chemical fat percentage, F&gt;M for water holding capacity and F&gt;M for percentage moisture. Terminal sire breed differences in the paired comparisons involving progeny of Chi (the comparisons with maximum degrees of freedom) indicated Chi progeny to have the highest color scores (darker cherry red) and C progeny the lowest (lighter cherry red), Chi progeny the lowest percentage chemical fat and C the highest, and Chi progeny the highest percentage moisture and C the lowest at both locations. At Brandon, the progeny ranking for Warner-Bratzler shear force was S&gt;Chi&gt;L, for pH Chi&gt;S = L, for texture score Chi&gt;C = S = L and Chi progeny had the lowest conformation scores and L progeny the highest. At Lacombe, significant progeny differences were recorded for Warner-Bratzler shear force with Chi&gt;L and for water retention capacity S&gt;Chi. At Brandon, breed of sire of dam effects indicated the progeny from S-cross dams had the highest texture scores. Progeny from L-cross dams had the lowest percentage chemical fat, the lowest skeletal maturity scores, and the highest percentage moisture. Progeny from C-cross dams had the highest conformation scores. At Lacombe, progeny from S-cross dams had the highest Warner-Bratzler shear force. At both locations, progeny from dams of Shorthorn breeding had the highest marbling scores. Direct comparison of progeny from exotic cross dams vs. progeny from HA dams at both locations indicated that the progeny from HA dams had lower color scores (lighter cherry red), a lower percentage moisture, higher marbling scores and a higher percentage chemical fat. At Lacombe, the HA dams had progeny with lower Warner-Bratzler shear force. At Brandon, the progeny from the HA dams had lower texture scores, higher firmness scores, a lower percentage protein and generally had lower conformation scores. The differences found between breeds of terminal sire and breed cross of dam for the traits evaluated are not of any commercial consequence. Key words: Cattle, breeds, carcass, quality

Comparison of the Effects of High and Low Voltage Electrical Stimulation on Quality‐Indicating Characteristics of Beef Carcasses

ABSTRACTElectrical stimulation, both high‐voltage (HVES; 55OV) and low‐voltage (LVES; 35V), resulted in brighter, more youthful appearing color of lean as compared to that of controls (not stimulated). There were no differences attributable to electrical stimulation for marbling or “heat‐ring” score. Contrasts were made between LVES‐A (35V), LVES‐B (60V) and nonstimulated sides. LVES‐A resulted in brighter color of lean but lower marbling scores than did LVES‐B. LVES‐B produced brighter lean color and lower “heat‐ring” scores as compared to that of controls. Use of LVES‐A resulted in higher marbling scores as compared to that of controls. “Shackled” sides of LVES (both A and B) carcasses had significantly higher incidences of iridescence and two‐toning than did the “Free” sides and the controls.

Effects of low voltage electrical stimulation on quality characteristics of young bulls fed to 14, 16 and 18 months of age (1984)

Low voltage electrical stimulation of young bulls at 30 to 45 min after bleeding resulted in a lower muscle pH, higher marbling score, lighter cherry red color and reduced incidence of heat ring formation when compared to non-stimulated controls. Ribeye steaks from electrically stimulated sides were more tender than non-stimulated controls, but bottom round steaks were not different. Our results indicate that low voltage electrical stimulation, incorporated into a continuous slaughter operation as late as 30 to 45 min after bleeding, can improve USDA quality characteristics and tenderness of meat from young bulls.

Characterization of Biological Types of Cattle (Cycle III).III. Carcass Composition, Quality and Palatability2

Composition, quality and palatability characteristics of 641 steer carcasses obtained from mating Hereford and Angus cows to Hereford or Angus (HAX), Tarentaise (TX), Pinzgauer (PX), Brahman (BrX) and Sahiwal (SaX) sires were compared after adjustment of data to equal age, weight, fat thickness, fat trim percentage and marbling end points. Ranking of sire breed groups for carcass weight (kg) at a constant age was: BrX(308), TX(297), HAX (296), PX(293) and SaX(285). Rankings of sire breed groups for compositional percentages at equal carcass weights were: retail product, BrX(71.0), TX(70.2), PX(69.4), SaX(68.3)and HAX(66.9); fat trim, HAX(20.9), SaX(19.4), PX(17.4), TX(17.1) and BrX(16.0); bone, PX(13.2), BrX(13.0), TX(12.7), SaX(12.3)and HAX(12.2). The positive relationship between ranking for growth rate and for retail product percentage agrees with data from previous cycles of breed groups indicating that growthier types tend to have leaner carcasses at comparable weights. Dressing percentages at a common carcass weight were higher for BrX and SaX(63.8 and 64.0%) and lower for PX(62.0%) than for HAX(63.2%) or TX(63.2%). Breed groups reached 19% fat trim at different live weights (kilograms): HAX(438), SaX(446), TX(475), PX(481) and BrX(483). At 19% fat trim, PX had the highest marbling scores and BrX and SaX the lowest (11.3 vs 9.7). HAX had the highest marbling score at age- and weight-constant end points. BrX and SaX had the lowest marbling scores at all end points. Taste panel evaluation revealed small but statistically significant differences among breed groups in flavor, juiciness and, particularly, tenderness. HAX and PX samples were more tender and BrX and SaX samples less tender than samples from other breed groups. Although all breed group averages were acceptable or higher, 0% of HAX, 4% of PX, 7% of TX, 14% of BrX and 20% of SaX carcasses had tenderness scores less than acceptable.

Heterosis and Management Effects in Carcass Characters of Angus, Hereford and Reciprocal Cross Cattle

Heterosis for carcass characters was estimated from Angus and Hereford crosses. Two data sets were analyzed. Data set I contained records of 1,095 calves placed on feed immediately after weaning. Data set II was made up of records on 210 calves assigned randomly to either immediate feeding or deferred management (wintering, grazing and then feeding). Cattle with Angus sires or dams produced heavier carcasses with higher dressing percentages, conformation scores, marbling scores and final grades, a larger percentage kidney fat and thicker fat cover but lower estimated cutability than cattle with Hereford sires or dams. Steers dressed higher, producing heavier carcasses with higher conformation scores and larger longissimus muscle areas, whereas heifers were fatter and graded higher. Carcasses from deferred cattle were heavier, with higher marbling scores and grades, less kidney fat, larger longissimus muscle areas and higher estimated cutability than carcasses of cattle fed immediately after weaning. Heterosis was observed for carcass weight, longissimus muscle area and measures of fatness in both data sets.

Effects of Breed and Age Classification on Live Weight and Carcass Traits of Steers Shown at International Quality Beef Show

Live weight and carcass data were collected on 1,419 Angus, 627 Hereford and 457 Shorthorn steers shown at the International Quality Beef Show from 1956 through 1967. These steers were grouped into three age classes. Herefords were the heaviest and Angus the lightest for live weight. Differences among breeds for carcass weight were small and non-significant. Hereford steers had the lowest unadjusted and adjusted fat thickness values and the lowest marbling scores of the three breeds. Angus had the largest area of longissimus and the highest marbling score while Shorthorn had the smallest area of longissimus. The two traits, for which breed effects were the largest, were area of longissimus and marbling score. Of the traits included in this study, these are the two traits that probably would be least influenced by environment. Although all comparisons among breeds for area of longissiums were significantly different (P<.05), the larger differences were due to the smaller longissimus area of the Shorthorn steers, (68.3 for Shorthorn vs. 75.5 and 74.3 cm2, respectively, for Angus and Hereford). Least square means for marbling score were 8.0, 7.4 and 6.8, respectively, for Angus, Shorthorn and Hereford. Live weight, carcass weight, area of longissimus, fat thickness, and marbling score significantly increased with increasing age as measured by age classification. Adjustment of longissimus area by dividing by carcass weight (a common adjustment in beef carcass evaluation) would not be recommended since areas of longissimus were larger and longissimus/100 kg of carcass were smaller for the older age classes. The covariate, carcass weight, greatly reduced differences among age classes for longissimus area and especially for fat thickness.