Physical, chemical, histological and palatability characteristics of muscles from three breed-types of cattle at different times-on-feed

Forty-five steers (9-12 months of age) of Angus (n =15), Brahman (n = 15) and Brahman × Angus (n = 15) breed-types were fed a high-energy diet and then slaughtered after 0, 112 or 224 days of feeding. At 7 days post mortem, the M. longissimus and M. biceps femoris were removed from the left side of each carcass and steaks were obtained for determination of sensory panel ratings, Warner-Bratzler shear force, sarcomere length, collagen content and collagen solubility. Tenderness ratings of steaks from the M. longissimus and M. biceps femoris from Angus were generally higher than ratings for steaks from Brahman or Brahman × Angus steers. Steaks from Brahman × Angus received higher tenderness ratings than steaks from Brahman steers in only a few comparisons. The three breed-types of cattle responded to time-on-feed differently; Brahman cattle needed to have been fed longer than Angus cattle to produce equally tender beef. With increased time-on-feed, M. longissimus tenderness increased for all breed-types, but M. biceps femoris tenderness was not related to time-on-feed. Few significant differences were observed among breed-types and among time-on-feed periods for collagen content or collagen solubility. Tenderness differences were closely correlated with the contractile state of the muscle which, in turn, was associated with weight, subcutaneous fat thickness and temperature decline of the carcass.     

Tenderness of major muscles from three breed-types of cattle at different times-on-feed

Seventy-five steers (9 to 12 months of age) of Angus (n = 25), Brahman (n = 25) and Brahman × Angus (n = 25) breed-types of known history were fed a high-energy diet and five steers from each breed-type were slaughtered after 0, 56, 112, 168 and 224 days on test. At seven days post mortem, the left side of each carcass was fabricated and eight major primals or subprimals were obtained. Steaks were removed from the shoulder clod, strip loin, tenderloin, top sirloin, knuckle, top round, bottom round and eye of round for Warner-Bratzler shear (WBS) determinations and from the strip loin and bottom round for sensory panel evaluations. Steaks from Angus and Brahman × Angus steers were generally more tender than steaks from Brahman steers. Tenderness of steaks from steers of the three breed-types responded to time-on-feed differently: (a) steaks from Brahman steers improved (P < 0·05) in tenderness with increasing time-on-feed for all muscles except the M. psoas major (tenderloin); (b) with the exception of the M. longissimus muscle (strip loin), the tenderness of steaks from Angus steers did not change (P > 0·05) as time-on-feed increased and (c) for the Brahman × Angus steers, five of the ten muscles studied improved (P < 0·05) in tenderness with increasing time-on-feed. 'Acceptable' tenderness (WBS values of less than 4·5 kg) for most of the muscles was achieved at feeding periods from 112 to 224 days for Brahman, from 0 to 56 days for Angus and from 56 to 168 days for Brahman × Angus.     

Effects of USDA feeder grade and time-on-feed on carcass characteristics and cooked beef palatability

Yearling feeder steers (n = 128), selected to vary in frame size and muscle thickness, were fed for 100, 130 or 160 days and then slaughtered. USDA grade data were collected and cooked rib steaks were evaluated for palatability attributes. Frame size was positively related to carcass weight and longissimus muscle area and negatively related to all fatness measures and to USDA yield grade. Steaks from large-framed steers received the lowest sensory panel ratings for juiciness and overall palatability. Muscle thickness of feeder steers was positively related to all measures of carcass muscling. Steaks from thinly muscled (No. 3) steers received higher ratings for juiciness and overall palatability than did steaks from thickly muscled (No. 1) steers. Large-framed or thickly muscled (No. 1) steers produced the lowest percentages of carcasses with at least Choice quality. Although some statistically significant differences were observed when the data were sorted by frame size or muscle thickness, few real trends were evident that would be of value to cattle feeders.     

Comparison of Subcutaneous Fat Thickness, Marbling and Quality Grade for Predicting Palatability of Beef

Beef from yearling steers (n = 254) which were fed either grass only or high-concentrate diets was used to study subcutaneous fat thickness as an alternative method for grading beef carcasses. Assigning carcasses to three expected-palatability groups based on fat thickness was at least equivalent to, and perhaps slightly more precise than, the use of USDA quality grades for grouping the carcasses according to expected palatability. There were progressive increases in palatability of cooked beef as fat thickness of carcasses from cattle fed 90–160 days increased from less than 2.53 mm up to 7.61 mm, but quantities greater than 7.61 mm did not further improve palatability.     

Characterization of cutability and palatability attributes among different slaughter groups of beef cattle

Fifteen slaughter cattle from five groups (Charolais crossbred bulls, Brahman crossbred steers, Holstein steers, mixed-Exotic crossbred heifers and Hereford-Angus crossbred steers) were randomly selected from a commercial feedlot. Time-on-feed was 108, 114, 102, 108 and 145 days for the aforementioned groups, respectively. Carcasses from Charolais crossbred bulls had the highest percentage yield of chuck and round, but the lowest percentage yield of loin; hereford-Angus crossbred steers had the lowest percentage yield of round and Holstein steers had the lowest percentage yield of rib. Carcasses from Charolais crossbred bulls had the highest percentage yield of major retail-ready subprimals and lean trim, Hereford-Angus crossbred steers had the highest percentage yield of fat trim and Holstein steers had the highest percentage yield of bone from the major wholesale cuts. Mean percentage yields of closely trimmed, boneless retail cuts were highest for carcasses from the bulls and lowest for carcasses from the Hereford-Angus steers. Although Holstein steer carcasses had less fat trim than Brahman-crossbred steers mixed-Exotic heifers, this advantage was largely offset by their higher percentage of bone. Loin steaks from carcasses of Charolais crossbred bulls, Holstein, mixed-Exotic heifers were comparable (P > 0·05)with those of Hereford-Angus steers for shear force and sensory panel tenderness ratings. However, loin steaks from carcasses of Brahman-crossbred steers had significantly higher (P < 0·05) shear force values (least tender) and lower (P < 0·05) tenderness and overall palatability ratings. No diffeerences (P > 0·05) were found for flavor desirability of loin steaks among any of the groups. For bottom round steaks, Hereford-Angus steers received the highest palatability ratings while those from Holstein steers received the lowest palatability ratings.     

SUPPLEMENTATION OF VITAMIN E TO BOVINE FEMALES IN "WHITE COW", MATURE BEEF, UPGRADING PROGRAMS

Forty cull cows were used to determine the effects of feeding supplemental dietary Vitamin E and a high-concentrate feedlot finishing diet on fresh meat retail caselife and oxidized flavor of roast beef from carcasses of such cows. They were either fed a feedlot finishing diet not supplemented with Vitamin E (control; N=8) or were fed a feedlot finishing diet supplemented with Vitamin E for 14, 28, 42 or 56 days (N=8 for each time-on-feed). During the feeding period, the 32 cows in treatment feeding groups had access to a total of 50,400 IU of supplemental Vitamin E; cows in the 14 day time-on-feed group received the highest daily dose (3,600 IU/day) and those in the 56 day time-on-feed group received the lowest daily dose (900 IU/day) of supplemental Vitamin E. On average, tissue α-tocopherol levels were increased from 2.39 μg/g (control) to 4.21–5.44 μg/g by 14–56 days of supplemental feeding. Supplemental feeding of dietary Vitamin E and a feedlot finishing diet had the greatest effect on the visual color and percent surface discoloration of top round and top sirloin steaks and had the least effect on the visual color and percentage surface discoloration of ground beef patties, tenderloin and strip steaks. Taste panelists were able to detect a slightly, but significantly, greater quantity of warmed-over flavor components in the control roast beef than in the roast beef from cattle fed supplemental dietary Vitamin E and a feedlot finishing diet.     

Palatability characteristics of loin steaks from Charolais crossbred bulls and steers

Loins from 1/2-blood or 3/4- to 7/8-blood Charolais bulls (n = 60) and steers (n = 64) were obtained at 24 h post mortem from electrically stimulated sides and, at 12 days post mortem, steaks were removed and frozen. Shear force values were higher (P < 0·001) and sensory panel evaluations of tenderness and overall palatability were lower (P < 0·001) for steaks from bulls than from steers. No differences (P > 0·05) in connective tissue amount or off-flavour were detected for steaks from bulls versus steers. Significant correlations between carcass secondary sex characteristics and sensory panel evaluations of tenderness were noted, but the coefficients were not of a magnitude to be considered predictive of tenderness.     

Technical note: feeding zilpaterol hydrochloride to calf-fed Holstein steers improves muscle conformation of top loin steaks

The objective of this research was to evaluate changes in the muscle conformation of subprimal top-loins (M. longissimus lumborum) from calf-fed Holstein steers fed zilpaterol hydrochloride (ZH). Top-loins (n = 100) were transversely cut into 2.54 cm-thick steaks, weighed, and objectively evaluated via image analysis software for muscle area, width, and length traits. Top-loin steaks from steers fed ZH were heavier (P< 0.01; 367 vs. 337 g) and average muscle area per steak was greater (P < 0.05; 80.9 vs. 77.2 cm(2)) as compared to steaks from control steers. Muscle width (medial-lateral) was not different (P = 0.23) between control steers and those fed ZH. However, steaks from steers fed ZH had greater (P < 0.05) depth (dorsal-ventral) than steaks from control steers throughout the top-loin. The increased muscle depth of top-loins from calf-fed Holstein steers fed ZH may improve the center-of-the-plate salability of a cut that has traditionally suffered from poor muscling.     

Effects of Certain Electrical Stimulation Parameters on Quality and Palatability of Beef

Grain-finished steers and heifers (n=390) were slaughtered in a commercial plant and assigned to one of five groups: (a) electrical stimulation (ES) immediately after exsanguination, (b) ES immediately before evisceration, (c) ES immediately after evisceration, (d) ES immediately after splitting, and (e) untreated (not ES). ES consisted of either 150 or 550 volts for either 1 or 2 mm. Electrically stimulated carcasses had more youthful, brighter colored lean and less “heat-ring” than untreated (not ES) carcasses. Steaks from electrically stimulated carcasses had (P<0.05) lower shear force values, were more tender, had less panel-detectable connective tissue and higher overall palatability ratings than did steaks from untreated (not ES) carcasses. Steaks from carcasses receiving 550-volt ES usually had more youthful, brighter colored lean and lower shear force values, were more tender, had less panel-detectable connective tissue and higher overall palatability ratings than steaks from carcasses that received 150-volt electrical stimulation. Quality and palatability traits of carcasses electrically stimulated for 1 mm were not different from those of carcasses receiving 2 mm of electrical stimulation. Electrical stimulation at different stages in the slaughter-dressing sequence did not evoke differential responses in quality or palatability factors.     

Reducing Postmortem Aging Time of Beef with Electrical Stimulation

Two studies (Study 1 = 23 forage-fed steers; Study 2 = 20 grain-fed steers and heifers) were conducted to determine relationships of electrical stimulation (ES) and/or postmortem aging (PA) to tenderness of beef. For Study 1, steaks from ES sides had lower (P < 0.05) Warner-Bratzler shear (WBS) values than steaks from not-ES sides for each PA period. In addition, the percentage reduction in WBS values was greater for the steaks from the ES-Day 2 group (–29.5%) than for steaks from even the longest PA period (14 days) from the not-ES group (–25.8%). For Study 2, during the fist three PA periods (1, 2 and 5 days), ES resulted in more desirable (P < 0.05) flavor ratings (Day l), higher (P < 0.05) tenderness ratings and lower (P < 0.05) WBS values (Day 1, 2, 5) and more desirable (P < 0.05) overall palatability ratings (Day 1, 2). During the last three PA periods (8, 11 and 14 days), ES resulted in higher (P < 0.05) tenderness ratings (Day 8), lower (P < 0.05) juiciness ratings (Day 11, 14) and lower (P < 0.05) WBS values (Day 8). Based on these results, ES had the greatest impact on beef palatability if the period of aging was 8 days or less; with additional aging time, ES effects on palatability were negated. When each treatment (ES, not-ES) was divided into two groups based on median tenderness ratings for the not-ES group, ES had the greatest impact on those carcasses in the “tough” group while ES had little impact on those carcasses in the “tender” group. ES will accelerate the postmortem aging of beef but the aging time reduction and extent of ultimate tenderization appears to be affected by the inherent tenderness of the beef.     

Consumer Acceptance of Steaks and Roasts from Charolais Crossbred Bulls and Steers

Forty-eight Charolais bulls (n=24) and steers (n=24) were commercially fed, slaughtered and subprimals were distributed to three retail stores. Consumers were able to detect differences in tenderness for steaks from the rib, loin and top sirloin of bulls and steers, but not for steaks or roasts from the round (except for the eye of round steak) and chuck of bulls and steers. However, 91.7% and 86.8% of the consumers of steaks from steers and bulls, respectively, indicated that they would purchase similar steaks again while 92.3% and 93.2% of the consumers of roasts indicated they would purchase similar roasts from steers and bulls, respectively.     

Comparison of sensory characteristics and fatty acid composition between Wagyu crossbred and Angus steers

Angus (n = 10) and crossbred (3/4 and 7/8) Wagyu (n = 10) steers were fed a diet according to typical Japanese standards for 552 days. The steers were fed to gain approximately 0·90 kg/head/day. Fatty acid composition was determined for subcutaneous and intramuscular adipose tissue, and M. longissimus dorsi muscle. Trained sensory evaluation and a consumer triangle test were performed on M. longissimus dorsi muscle steaks. For subcutaneous and intramuscular tissue. Wagyu adipose tissue possessed higher (P < 0·05) percentages of 14:1, 16:1 and 18:1 and a lower (P < 0·05) percentage of 16:0 and 18:0 than corresponding tissues from Angus steers. Trained sensory panel analysis revealed no differences (P < 0·05) in any of the sensory traits between steaks from Wagyu crossbred and Angus steers. However, a consumer triangle test indicated that consumers can detect a difference between breeds.     

Effects of dietary vitamin A restriction during finishing on color display life, lipid oxidation, and sensory traits of longissimus and triceps brachii steaks from early and traditionally weaned steers

Our objective was to determine the effects of vitamin A restriction during finishing on color display life, lipid oxidation, and sensory traits of longissimus lumborum (LL) and triceps brachii (TB) steaks from early and traditionally weaned steers. Forty-eight steers weaned at either 137 ± 26 days (EW) or 199 ± 26 days (TW) were supplemented with either 15,400 IU/kg dry matter of vitamin A (HA) or restricted to no supplemental vitamin A (LA) during finishing for 210 and 150 days, respectively. Both LL and TB steaks from the HA steers had the darkest (P < 0.05) color scores after 3 days of retail display in PVC packaging at 2 °C, and the highest (P < 0.05) thiobarbaturic acid reactive substances (TBARS) values. Instrumental a∗, b∗, and saturation index values were lowest (P < 0.05) in LL steaks from the HA steers. Instrumental L∗ values were lower (P < 0.05) on days 4–6 in TB steaks from TW steers fed LA than those from EW steers fed HA. No differences were found in Warner–Bratzler shear force values or sensory traits in either muscle. No supplemental vitamin A versus high levels of vitamin A inclusion in finishing diets has potential to increase color display life and reduce lipid oxidation, with no effects on meat palatability.     

THE EFFECT OF ELECTRICAL STIMULATION ON THE PALATABILITY AND CONSUMER ACCEPTANCE OF BONELESS RIB STEAKS

A total of 25 cattle (5 purebred Simmental, Limousin, or Chianina bulls and 10 each of steers and heifers (1/2 blood Simmental, Limousin, or Chianina) 11 to 15 months of age and with carcasses weighing approximately 270 kg, after approximately 255 days on a high concentrate ration, were utilized to evaluate the effects of electrical stimulation upon the palatability and consumer acceptance of boneless rib steaks. The right side of each carcass was electrically stimulated at 400 V (AC 50 to 60 cycles/sec) using a hog stunner with a maximum output of 5 amps, immediately after splitting, while the left side served as an unstimulated control. Boneless rib steaks were presented to an experienced taste panel (1/side) and distributed to household consumers (4/side) for evaluation of overall tenderness and the acceptability of flavor, juiciness, tenderness, and overall palatability. Significant (P <0.05) treatment effects were not observed in cooking losses, consumer acceptance, or any of the palatability attributes evaluated, indicating that prerigor electrical stimulation, prior to chilling, did not produce meaningful differences in these traits, with the type of cattle and conditions employed in this study.     

EFFECT OF ELECTRICAL STIMULATION AND BLADE TENDERIZATION ON PALATABILITY OF BEEF LONGISSIMUS AND SEMIMEMBRANOSUS MUSCLES

The effect of electrical stimulation (ES) and/or blade tenderization (BT) on palatability of longissimus (LD) and semimembranosus (SM) muscles from range-grazed and concentrate-fed steers were compared. Range-grazed steers graded lower and the steaks contained less fat and more moisture (P<0.05) than those from concentrate-fed steers. Broiled steaks from the range-grazed steers were less flavorful, less juicy, and less desirable overall than those from concentrate-fed steers (P<0.05). Nevertheless, tenderness of ES and BT treated steaks from range-grazed steers was comparable to steaks from concentrate-fed animals that had not been tenderized. Flavor and juiciness of LD muscle did not change with ES or BT treatments but flavor and juiciness of SM muscle decreased when combined ES and BT treatments were used.     

Effects of diet on rumen proliferation and fecal shedding of Escherichia coil O157:H7 in calves

Calves inoculated with Escherichia coli O157:H7 and fed either a high-roughage or high-concentrate diet were evaluated for rumen proliferation and fecal shedding of E. coli O157:H7. Calves fed the high-roughage diet had lower mean rumen volatile fatty acid concentrations and higher rumen pH values than did calves fed the high-concentrate diet. Despite these differences in rumen conditions, the calves fed the high-roughage diet did not have greater rumen populations of E. coli O157: H7 and did not exhibit increased or longer fecal shedding compared with the calves fed the high-concentrate diet. Two calves shedding the highest mean concentrations of E. coli O157:H7 were both fed the high-concentrate diet. There was a significant (P < 0.05) positive correlation between fecal shedding and rumen volatile fatty acid concentration in calves fed a high-concentrate diet. The effects of diet on E. coli O157:H7 proliferation and acid resistance were investigated using an in vitro rumen fermentation system. Rumen fluid collected from steers fed a high-roughage diet, but not from steers fed a high-concentrate diet, supported the proliferation of E. coli O157:H7. Rumen fluid from steers fed a high-concentrate diet rapidly induced acid resistance in E. coli O157:H7. The impact of diet on fecal shedding of E. coli O157:H7 is still unclear and may depend on dietary effects on fermentation in the colon and on diet-induced changes in the resident microflora. However, rapid development of acid tolerance by E. coli O157:H7 in the rumens of calves fed high-concentrate diets, allowing larger populations to survive passage through the acidic abomasum to proliferate in the colon, may be one factor that influences fecal shedding in cattle on feed.     

Fatty acid profiles,meat quality,and sensory attributes of organic versus conventional dairy beef steers

Meat from Holstein and crossbred organic and conventional dairy steers were evaluated and compared for fatty acid profiles, meat quality, sensory attributes, and consumer acceptance. Bull calves (n = 49) were randomly assigned to 1 of 3 replicated groups: conventional (CONV), organic (ORG, pasture + concentrate), or grass-fed organic (GRS) and were born at the University of Minnesota West Central Research and Outreach Center (Morris, MN) between March and May 2011. The CONV steers (n = 16) were fed a diet that contained 80% concentrate and 20% forage, and ORG steers (n = 16) were fed a diet of organic corn, organic corn silage, and organic protein supplement. Furthermore, ORG steers consumed at least 30% of diet dry matter of high-quality organic pasture during the grazing season. The GRS steers (n = 17) consumed 100% forage from pasture during the grazing season and high-quality hay or hay silage during the nongrazing season. The ORG steers had fat that was greater in oleic acid (C18:1) than the GRS and CONV steers (47.1, 36.1, and 39.9%, respectively). The GRS steers (21.9%) were lower for monounsaturated fat than the ORG (42.1%) and CONV (40.4%) steers. Furthermore, the GRS steers tended to have greater n-3 fat and had lower n-6 fat than the ORG and CONV steers. Consequently, the GRS (1.4%) steers had a lower n-6-to-n-3 fat ratio than the ORG (12.9%) and CONV (10.0%) steers. The GRS (2.6 kg) steers had steaks that were not different for Warner-Bratzler shear force than ORG (2.3 kg) steaks; however, the GRS steaks tended to have greater shear force than the CONV (2.0 kg) steaks. The 3 steer group had steaks that were not different for color brightness (L*; 0 = black and 100 = white) and yellowness/blueness (b*; positive values = yellow and negative values = blue) values; however, the GRS (10.5) steaks had lower redness/greenness (a*; positive values = red and negative values = green) values than CONV (14.5) steaks. For sensory attributes (0- to 120-point scale), no differences were observed for ORG (71.3) and CONV (69.2) steers for overall consumer liking of the beef; however, the GRS (56.3) steers had the lowest overall liking among beef consumers. The ORG (73.3) steers had greater flavor liking than the GRS (56.8) and CONV (69.2) steers. Conversely, the GRS (6.3) steers had the highest scores for off-flavor (0- to 20-point scale) compared with the ORG (3.9) and CONV (4.1) steers. The results of the current study suggest that a potential market may exist for organic grass-fed dairy steers in the United States, but quality and consistency of the beef needs to be improved.     

Flavor Constituents of Beef as Influenced by Forage- and Grain-Feeding

Hereford yearling steers (N= 144) were alloted to one of three pasture systems: tall fescue, smooth bromegrass-red clover or orchardgrass-red clover. After the grazing period, steers were finished in drylot and then serially slaughtered at 0, 56, 84 and 112 days. Carcass quality grades and yield grade numbers increased when steers were fed grain up to 112 days. Tenderness of loin steaks increased up to 84 days, after which no improvements were observed. Sensory panel scores for grassy flavor of steaks and ground beef decreased up to 112 days. Fifty-three compounds were identified in the volatiles of melted subcutaneous fat by direct sampling-gas chromatography/mass spectro-metry. The major differences between volatiles from fat of forage-fed compared to grain-fed steers were the higher concentrations of 2,3-octanedione and various diterpenoids present in the samples of the forage-fed animals.     

Meat color stability affected by barley variety fed in finishing diet to beef steers

Angus crossbred steers were assigned randomly to one of four finishing diets based on corn, Chinook, Logan, or H3 barley. Steers were harvested and after a 72-h chill, carcass quality and yield grade data were collected. Beef ribs were removed from 72 carcasses for further analysis. Ribs were aged in vacuum bag at 2 °C for 14 days. After aging three adjacent steaks (3.18 cm) were removed to determine color stability, tenderness, proximate analysis and pH. Diets fed to steers had no effect on quality and yield grade or tenderness of beef steaks. Steaks from steers fed Logan barley variety were significantly less red at 10 days of storage (Hunter a* = 24.06) than steaks from steers fed the other barley varieties (Chinook a* = 26.4; H3 a* = 28.05) or corn (a* = 26.14). Identification of barley varieties that affect color stability could result in designing diets specifically for improved color and increase the use of barley as a finishing grain.