Evaluating consumer acceptability of various muscles from the beef chuck and rib

One hundred thirty-eight consumers evaluated steaks from the complexus (CX), infraspinatus (IF), serratus ventralis (SV), supraspinatus (SS), and triceps brachii (TB) from the wholesale beef chuck; the deep pectoral (DP) from the wholesale brisket; and the longissimus thoracis (LT) from the wholesale rib. The LT was used as a reference for comparison to the other muscles. Ten USDA Choice and ten USDA Select boneless boxed beef subprimals were used for each muscle. Subprimals were aged 14 d from box date, frozen, and cut into 2.5-cm-thick steaks. Consumers rated the IF highest (P < 0.05) for overall like, tenderness, juiciness, and flavor, and assigned it the highest (P < 0.05) price/0.45 kg. The TB also was rated higher (P < 0.05) than the LT for overall like, tenderness, juiciness, flavor, and price/0.45 kg. The SV and CX were rated as being similar (P < 0.05) to the LT for overall like, tenderness, juiciness, flavor, and price/0.45 kg. Consumers rated the SS lower (P < 0.05) than the LT for tenderness, juiciness, flavor, and price. The DP was rated as the toughest, driest, and blandest (P < 0.05), resulting in assignment of the lowest (P < 0.05) price/0.45 kg. Differences in palatability ratings due to quality grade were found for several muscles; USDA Choice SV and SS were rated higher (P < 0.05) for overall like, tenderness, and juiciness than USDA Select SV and SS. For the IF, USDA Choice was rated higher (P < 0.05) for tenderness and juiciness than USDA Select. The USDA Choice TB was rated higher (P < 0.05) for juiciness, and the USDA Choice DP was rated higher (P < 0.05) for overall like, than their USDA Select counterparts. Tenderness, juiciness, and flavor ratings were correlated with overall like ratings (r = 0.84, 0.77, and 0.76, respectively) and with price (r = 0.73, 0.70, and 0.68, respectively). These results indicate the IF, TB, SV, and CX were acceptable, whereas and the SS and DP were unacceptable as steaks.     

Evaluating consumer acceptability and willingness to pay for various beef chuck muscles

In-home consumer steak evaluations, followed by centralized laboratory-setting auctions, were used to determine consumer (n = 74 consumers) acceptability and willingness to pay for various beef chuck muscles. The infraspinatus (IF), serratus ventralis (SV), supraspinatus (SS), and triceps brachii (TB) from the beef chuck were evaluated against LM steaks from the rib to determine price and trait differentials. Muscles from USDA Choice, boneless, boxed-beef sub-primals were aged 14 d, frozen, and cut into 2.5-cm-thick steaks. Consumers received two steaks from each muscle for in-home evaluations of uncooked steak appearance and cooked steak palatability. After in-home evaluation of steaks, consumers participated in a random nth price auction session to determine willingness to pay for those steaks. Muscles differed (P < 0.05) for overall like of appearance, like of size, like of shape, and like of leanness; LM generally rated the highest. Steaks from the LM rated highest (P < 0.05) for overall like, and steaks from the SS and SV were lowest (P < 0.05) for overall like. Juiciness and beef flavor intensity scores were highest (P < 0.05) for steaks from the LM and IF, whereas SS steaks received the lowest (P < 0.05) juiciness scores, and SS and SV steaks were rated lowest (P < 0.05) for beef flavor intensity. Average auction price differentials differed (P < 0.05) from the LM, and were -0.71 dollars, -0.79 dollars, -1.75 dollars, and -2.44 dollars/0.45 kg for the TB, IF, SS, and SV, respectively. Average appearance trait differentials and average palatability trait differentials were correlated significantly with average price differentials. Results indicate the IF and TB were acceptable to consumers as steaks but only at prices lower than the LM.     

Characterization of certified Angus beef steaks from the round, loin, and chuck

Beef carcasses (n = 150) of A-maturity were selected randomly to determine baseline shear force and sensory panel ratings, assess variation in tenderness, and evaluate mean value differences between Certified Angus Beef (CAB), commodity Choice, and Select steaks. Three steaks were removed from the triceps brachii (TB), longissimus lumborum (LL), gluteus medius (GM), semimembranosus (SM), biceps femoris (BF), and quadriceps femoris complex (QF), and assigned to Warner-Bratzler shear (WBSF) and sensory panel analyses. As anticipated, marbling score and measured percentage of i.m. fat were greatest (P < 0.05) for CAB, intermediate (P < 0.05) for Choice, and least (P < 0.05) for Select carcasses. A muscle x quality level interaction (P < 0.05) was observed for WBSF values and sensory panel tenderness ratings. The TB, LL, GM, and BF steaks from CAB carcasses had lower (P < 0.05) WBSF than Select steaks from the same muscles. Even though WBSF values did not differ (P > 0.05) between CAB and Choice QF and TB steaks, the LL and GM steaks from CAB carcasses were more tender (P < 0.05) than Choice-grade LL and GM steaks. The TB from Select carcasses had higher (P < 0.05) WBSF values than TB steaks from CAB or Choice carcasses, but sensory panel ratings indicated that quality level showed little consistency among the GM, SM, BF, and QF. Trained sensory panelists rated CAB LL steaks more tender (P < 0.05) than LL steaks from Choice and Select carcasses, and Choice LL steaks were evaluated as more (P < 0.05) tender than those from Select carcasses. These results demonstrate that the influence of marbling on tenderness was more evident in muscles of middle meats than in end cuts, particularly in muscles of the round.     

Fiber-type composition of muscles of the beef chuck and round

Thirty-eight muscles of the beef chuck and round were histochemically stained to characterize fiber-type composition in order to facilitate optimal muscle use in value-added products. Select-grade chucks and rounds (n = 4 each) were chosen to represent two carcass weight classes (250 to 295 kg and 363 to 410 kg) and two yield grades (1 and 3). Muscles were sectioned and stained with a procedure that included a succinate dehydrogenase and an adenosine triphosphatase staining technique. Number and diameter of beta-red, alpha-red, and alpha-white muscle fibers were used to determine muscle fiber percentage, muscle fiber area, and percent area in each muscle. Weight did not significantly (P > 0.05) affect these muscle fiber-type characteristics, probably because of limited sample numbers. Muscles containing greater than 40% beta-red fibers were classified as red; greater than 40% alpha-white fibers were classified as white. All other muscles were classified as intermediate. Nine of 12 round muscles were white, including semitendinosus, biceps femoris, rectus femoris, adductor, and semimembranosus. The chuck muscles were red (10 of 26), intermediate (9 of 26), and white (7 of 26). These data indicate variable fiber-type composition of most of the muscles of the beef chuck and round. Functional and biochemical traits of each muscle fiber class would be expected to create different processing characteristics, which would influence optimal muscle use in value-added products.     

Flavor relationships among muscles from the beef chuck and round

This research compared off-flavor notes and the relationship of pH and heme-iron content to off-flavor for different beef muscles. After grading, knuckles and shoulder clods were removed from 16 USDA Choice and 14 USDA Select beef carcasses, vacuum-packaged, and aged for 7 d. The rectus femoris (REC), vastus medalis (VAM), vastus lateralis (VAL), teres major (TER), infraspinatus (INF), and triceps brachii-long head (TRI) were separated, cut into steaks, and frozen (-16 degrees C). Sensory analysis was conducted using a trained taste panel, with steaks grilled to an internal temperature of 65 degrees C. Heme-iron concentration and pH were determined. The INF had lower (P < 0.05) off-flavor intensity ratings and less frequent sour flavor than the other muscles, and the VAL had the most intense (P < 0.05) off-flavor ratings and among the greatest frequency of sour, charred, and oxidized flavors. The frequencies of liver-like, bloody, and rancid flavors were not affected by muscle type. Heme-iron concentration did not differ among muscles. Three USDA Select carcasses had intense off-flavor in the muscles. Liver-like flavor was highly negatively correlated with off-flavor intensity for each of the muscles tested. Muscles rated a 5 or below (on an 8-point rating scale, where 1 = extremely intense off-flavor and 8 = no off-flavor) in off-flavor intensity and identified as liver-like by 30% or more of the panelists were grouped together and compared to normal muscles. Those in the liver-flavored group were less frequently identified as charred, probably because the liver-like flavor was so intense. There were no differences between the 2 groups for sour, metallic, bloody, oxidized, or fatty off-flavor notes. Regression equations containing the linear and quadratic functions of heme-iron concentration, muscle pH, and their interaction were established for the frequency of off-flavor notes within each muscle. The REC, TER, VAL, and VAM showed a relationship between pH, heme iron, and off-flavor intensity (P < 0.05). Liver-like flavor was explained partially by pH and heme iron in the REC, VAM, and VAL (R2 = 0.45 to 0.55; P < 0.05). Few other significant relationships were found. Heme iron and pH were unrelated to metallic, oxidized, or rancid flavors for any of the muscles tested. These data suggest that liver-like off-flavors are specific to individual animals, and that pH and heme iron are not strongly related to off-flavor notes.     

Intramuscular tenderness variation within four muscles of the beef chuck

The i.m. tenderness variation was examined within four beef chuck muscles, the infraspinatus (IF), supraspinatus (SS), triceps brachii (TB), and serratus ventralis (SV). The IF, SS, TB, and SV muscles were cut into 2.5 cm thick steaks perpendicular to the long axis of the muscle. An identification tag was placed on each steak, consisting of a muscle identification number, steak number, and orientation of the steak. Steaks were vacuum-packaged and stored at -22 degrees C until subsequent analysis. Steaks were thawed at 1 degrees C and cooked on electric broilers to an internal temperature of 71 degrees C. One core was removed from each 2.5-cm x 2.5-cm section parallel to the muscle fiber and sheared once to determine Warner-Bratzler shear force (WBSF). The SS had an overall WBSF mean of 5.43 kg (SD = 2.20 kg) with no tenderness difference (P = 0.43) among steak locations. The IF had an overall WBSF mean of 3.16 kg (SD = 1.01 kg) with no tenderness difference (P = 0.51) among steak locations. The SV had a mean WBSF value of 4.37 kg (SD = 1.27 kg) with tenderness variation (P < 0.05) among steak locations; however, tenderness variations were not dispersed in a discernible pattern. The TB had a mean WBSF value of 4.12 kg (SD = 1.26 kg) with lower (P < 0.05) shear force in the middle region of the TB, and the distal and proximal ends were tougher (P < 0.05). Results of this study provided a reasonably detailed mapping of the tenderness regions within the IF, SS, TB, and SV muscles, and this information could be used to add value to the beef chuck by cutting and marketing consistently tender regions.     

Enhancement of beef chuck and loin muscles with ammonium hydroxide and salt

The objective of this study was to evaluate the tenderness of beef chuck and round muscles when enhanced with ammonium hydroxide and salt at different pump levels. A randomized, complete block design of 4 treatments and 3 muscles with 3 replications was used, with a total of 15 subprimals per treatment. Treatments included a 0% (CON), 15% (T15), 22.5% (T22), and 30% (T30) target pump. The triceps brachii (TB), biceps femoris (BF), and rectus femoris (RF) muscles were studied. Muscles were injected with a solution of ammonium hydroxide and sodium chloride (patent-pending technology from Freezing Machines Inc., Dakota Dunes, SD). Individual steaks were cut to a thickness of 2.54 cm, vacuum-packaged in trays, and frozen. Warner-Bratzler shear force, pH, and sensory evaluations were determined. Shear force decreased as the target pump percentage increased for all muscles (P < 0.050): TB = 39.9, 35.1, 32.1, and 27.0 N; BF = 39.4, 26.2, 23.3, and 19.3 N; RF = 42.7, 32.9, 30.7, and 28.9 N for CON, T15, T22, and T30, respectively. In all cases, there were no shear force differences between T15 and T22 (P > 0.050). As percentage pump increased, pH increased. The ultimate pH was moderately strongly to strongly related to shear force (r = 0.55, 0.70, and 0.80 for RF, TB, and BF, respectively). Trained taste panel ratings revealed an increase in tenderness, decrease in connective tissue, and an increase in juiciness as pump level increased for all muscles. In all cases but one (juiciness of the RF), the CON had the least desirable ratings and shear force values (P < 0.050). There were no major differences between T15 and T22, and T30 steaks tended to have an uncharacteristic soft and mushy texture. For this reason a 20% target pump level was determined to be the optimum pump level. These data suggest that adjusting pH in beef with ammonium hydroxide and salt can increase tenderness in muscles from the beef chuck and round. Any level of treatment was beneficial, with the greatest shear force benefit occurring in muscle pumped to 30%.     

Relationship between longissimus composition and the composition of other major muscles of the beef carcass

Left sides from 18 beef carcasses (9 steers and 9 heifers), selected to represent a wide range of marbling scores, were evaluated to determine the relationship between longissimus composition and the composition of other major muscles. The adductor (A), biceps femoris (BF), deep pectoral (DP) gluteal group (GL), infraspinatus (I), longissimus (L), psoas major (PM), rectus abdominis (RA), rectus femoris (RF), semimembranosus (SM), semitendinosus (ST), serratus ventralis (SV), spinalis (SP), supraspinatus (SU) and triceps brachii (TB) were removed, trimmed of external fat, weighed and ground for proximate analysis. Fat content of all muscles was related linearly (P less than .001) to L fat content (R2 values ranged from .67 to .84). The ST had the lowest mean fat content (4.4%) and SP had the highest mean percentage of fat (16.1%). The L ranged from 3.59% to 15.42% fat with a mean of 8.61%. Longissimus fat percentage can be used to predict the fat content of the other major muscles of the beef carcass.     

Relationship between marbling group and major muscle contribution to beef carcass mass

Left sides from 18 beef carcasses (9 steers and 9 heifers) were divided equally among three marbling groups (low = traces or slight; intermediate = small or modest; high = slightly abundant) and evaluated to determine the relationship between longissimus composition and the percentage each major muscle contributes to the weight of the beef carcass. The adductor (A), biceps femoris (BF), deep pectoral (DP), gluteal group (GL), infraspinatus (I), longissimus (L), psoas major (PM), rectus abdominis (RA), rectus femoris (RF), semimembranosus (SM), semitendinosus (ST), serratus ventralis (SV), spinalis (SP), supraspinatus (SU) and triceps brachii (TB) were removed, trimmed of external fat and weighed. Muscle weights were expressed as a percentage of hot carcass weight: A = .76%; BF = 3.30%; DP = 1.89%; GL = 1.81%; I = 1.10%; L = 3.35%; PM = .95%; RA = 1.12%; RF = .94%; SM = 2.35%; ST = 1.14%; SV = 2.26%; SP = .82%; SU = .69% and TB = 1.83%. The deep pectoral and triceps brachii were heavier (P less than .05) in steer carcasses than in heifer carcasses. No other significant sex effects were noted. Percentage of muscle tended to decrease with increasing marbling level; however, the linear regression of relative muscle weight on marbling level was significant for the BF, DP, PM, SM, SU and TB. Using marbling score or yield grade factors to predict the percentage of individual muscles in the carcass resulted in R/ values greater than .4 in 7 of the 15 muscles evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of restricted feeding of beef heifers during the postweaning period on growth, efficiency, and ultrasound carcass characteristics

Traits used for identification of replacement beef heifers and feeding levels provided during postweaning development may have major financial implications due to effects on maintenance requirements and level of lifetime production. The current study evaluated the effects of 2 levels of feeding during the postweaning period on growth, G:F, and ultrasound carcass measurements of heifers, and the associations among these traits. Heifers (1/2 Red Angus, 1/4 Charolais, and 1/4 Tarentaise) born in 3 yr were randomly assigned to a control (fed to appetite; n = 205) or restricted (fed at 80% of that consumed by controls adjusted to a common BW basis; n = 192) feeding during a 140-d postweaning period. Heifers were individually fed a diet of 68% corn silage, 18% alfalfa, and protein-mineral supplement (DM basis) in pens equipped with Calan gates. Ultrasound measurements of LM area, intramuscular fat, and subcutaneous fat thickness over the LM were made on d 140 (382 +/- 0.8 d of age). Average daily DMI was 4.1 and 5.6 kg/d for restricted and control heifers, respectively (P < 0.001). Feed restriction decreased (P < 0.001) BW (292 vs. 314 kg), ADG (0.52 vs. 0.65 kg/d), LM area (55 vs. 59 cm2), intramuscular fat (3.2 vs. 3.5%), and subcutaneous fat thickness over the LM (3.2 vs. 3.9 mm), but increased G:F (0.12 vs. 0.11) when compared with control at the end of the 140-d study. The magnitude of the associations of DMI with ADG (r = 0.32 vs. 0.21), 140-d BW (r = 0.78 vs. 0.36), hip height (r = 0.57 vs. 0.17), LMA (r = 0.30 vs. 0.18), and BCS (r = 0.17 vs. 0.11) was greater in restricted- than control-fed heifers. Variance of residual feed intake, calculated within each treatment, was greater (P < 0.01) in control (0.088) than restricted (0.004) heifers, and magnitude of association between residual feed intake and average DMI was greater in control (r = 0.88) than restricted (r = 0.41) heifers. Pregnancy rate tended (P = 0.11) to be reduced in heifers that had been developed on restricted feeding (86.3 +/- 2.3 vs. 91.5 +/- 2.3%). However, ADG was greater (P < 0.001) in restricted than control heifers (0.51 vs. 0.46 kg/d) while grazing native range in the 7 mo after restriction. In summary, restricted heifers consumed 22% less feed on a per-pregnant-heifer basis during the development period and had a greater magnitude of association between DMI and several growth-related traits at the end of the 140-d postweaning feeding period, which is indicative of improved efficiency.     

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).     

Association between IGF-I, IGF-IR and GHRH gene polymorphisms and growth and carcass traits in beef cattle

Molecular biology techniques are of help in genetic improvement since they permit the identification, mapping and analysis of polymorphisms of genes encoding proteins that act on metabolic pathways involved in economically interesting traits. The somatotrophic axis, which essentially consists of growth hormone releasing hormone (GHRH), growth hormone (GH), insulin-like growth factors I and II (IGF-I and IGF-II), and their associated binding proteins and receptors (GHRHR, GHR, IGF-IR and IGF-IIR), plays a key role in the metabolism and physiology of mammalian growth. The objectives of the present study were to estimate the allele and genotype frequencies of the IGF-I/SnaBI, IGF-IR/TaqI and GHRH/HaeIII gene polymorphisms in different genetic groups of beef cattle and to determine associations between these polymorphisms and growth and carcass traits. For this purpose, genotyping was performed on 79 Nellore animals, 30 Canchim (5/8 Charolais+3/8 Zebu) animals and 275 crossbred cattle originating from the crosses of Simmental (n=30) and Angus (n=245) sires with Nellore females. In the association studies, traits of interest were analyzed using the GLM procedure of SAS and least square means of the genotypes were compared by the Tukey test. Associations of IGF-I/SnaBI genotypes with body weight and subcutaneous backfat were significant (p<0.05), and nearly significant for longissimus dorsi area (p=0.06), with the BB genotype being favorable compared to the AB genotype. No significant associations were observed between this polymorphism and weight gain or carcass yield (P>0.05). The IGF-IR/TaqI and GHRH/HaeIII polymorphisms showed no association with production traits.     

育肥肉牛屠宰率与活体、胴体价格之间的关系分析

为探讨育肥牛屠宰率与活体、胴体价格之间存在的关系,为促进肉牛屠宰加工企业按质论价提供参考。本文从屠宰场收购育肥牛的日常价格入手,利用3个时间段的具体事例,通过假设类推法开展分析研究。结果表明,活胴价比等于盈亏平衡点屠宰率,盈亏平衡点屠宰率与胴体价格呈反向变化规律。在现实交易中,与活胴价比相等的那个屠宰率的点上出售活体牛与胴体收益相等,但是胴体价格会有相应的变化,双方相互兼顾,争取利益最大化。     

Evaluation of estimated genetic merit for carcass weight in beef cattle: Blood metabolites, carcass measurements, carcass composition and selected non-carcass components

In Ireland, a new beef genetic index has been developed. Growth rate is expressed as expected progeny difference for carcass weight (EPD_CWT) and is estimated on an across-breed basis. Cross-breeding of dairy cows with both Aberdeen Angus and Belgian Blue beef sires is widely practised. The objective of this study was to compare blood metabolites, slaughter traits and carcass composition of progeny from Holstein–Friesian dairy cows and Aberdeen Angus (AA), Belgian Blue (BB), Friesian (FR) and Holstein (HO) sires. The AA and BB sires were selected, within breed, to be of either high (H) or low (L) estimated genetic merit for carcass weight. A total of 170 male progeny from spring-calving cows and 42 sires (10 AA, 13 BB, 7 FR and 12 HO) were artificially reared indoors and managed together until the end of their second grazing season when they were assigned to either a Light (560 kg) or Heavy (620 kg) slaughter weight. Blood metabolite concentrations were measured six times throughout life and feed intake was recorded during the first and second winter. Carcass measurements and selected non-carcass components were recorded after slaughter and the right side of each carcass was dissected into lean, fat and bone. Differences in blood metabolite concentrations amongst genetic groups were negligible although there were some effects of the prevailing level of nutrition. M. longissimus area scaled for carcass weight was 0.220, 0.221, 0.260, 0.255, 0.212 and 0.208 (SE 0.004) cm²/kg for AAH, AAL, BBH, BBL, FR and HO, respectively. Carcass measurements scaled for carcass weight were greater for L, AA, HO and the dairy strains than for H, BB, FR and the beef breeds, respectively. There was no effect of estimated genetic merit for carcass weight on carcass composition. Statistically significant interactions between genetic merit and beef breed existed for some traits with the genetic merit effect largely evident for AA only. BB and the beef breeds had more lean, less fat and more high value lean in the carcass than AA and the dairy strains, respectively. It is concluded that genetic group had little effect on blood metabolite concentrations but there were some feeding level effects. Estimated genetic merit for carcass weight affected carcass weight, m. longissimus area and carcass measurements scaled for carcass weight but the effects were confined to AA. There were large effects of beef breed and dairy strain on carcass composition.     

Effects of repetitive use of hormonal implants on beef carcass quality,tenderness, and consumer ratings of beef palatability

Effects of repetitive use of anabolic implants on beef carcass quality, tenderness, and consumer ratings for palatability were investigated using crossbred steer calves (n = 550). Steers from five ranches were randomly allocated to one of 10 different lifetime implant strategies or to a nonimplanted control group. Cattle were implanted at some or all of five phases of production (branding, weaning, backgrounding, feedlot entry, or reimplant time). Carcasses from the control group had higher (P < 0.05) marbling scores than carcasses from steers in all other treatment groups. Implanting steers at branding, weaning, or backgrounding vs. not implanting steers at these production stages did not affect (P > 0.05) marbling scores. Steers implanted twice during their lifetime produced carcasses with higher (P < 0.05) marbling scores than did steers receiving a total of four or five implants. Steaks obtained from carcasses in the control group had lower (P < 0.05) shear force values and were rated by consumers as more desirable (P < 0.05) for tenderness like/dislike than steaks obtained from carcasses in all other treatment groups. Implanting steers at branding or weaning production stages did not affect (P > 0.05) steak shear force values, consumer ratings for like/dislike of steak tenderness, or percentage of consumers rating overall eating quality of steaks as satisfactory. Implanting steers at backgrounding vs. not implanting steers at this production stage increased (P < 0.05) steak shear force values, but did not influence (P > 0.05) consumer ratings for like/dislike of steak tenderness or percentage of consumers rating overall eating quality of steaks as satisfactory. Steaks from nonimplanted steers were rated as more desirable (P < 0.05) for overall eating quality than steaks from steers implanted two, three, four, or five times. Use of implants increased (P < 0.05) average daily gain by 11.8 to 20.5% from weaning to harvest compared with nonimplanted controls. Implant strategies increased (P < 0.05) hot carcass weight of steers by 8.9 to 13.8% compared with the control group. Use of implants also increased (P < 0.05) longissimus muscle area and decreased (P < 0.05) estimated percentages of kidney/pelvic/heart fat, but did not affect (P > 0.05) dressing percentage or adjusted fat thickness. Our findings suggest that beef quality, palatability, and production characteristics are influenced by lifetime implant protocols.     

Intake,digestibility, performance,and carcass traits of beef cattle of different gender

The performance, intake, feed efficiency, and carcass traits of beef cattle from different gender profile were assessed. Fifteen animals (five steers, five spayed heifers, and five intact heifers) with ±250 kg of initial body weight were randomly assigned in individual pens and fed the same diet for 106 days. At the end of the trial, all the animals were slaughtered and the pH, temperature, and weight of the carcass were recorded. The right side of each carcass was then separated into chuck, shoulder, flank sirloin, and round for evaluation of commercial cuts yield. The left carcass sides were ribbed between the 12th and 13th ribs where the rib eye area and fat thickness measurements were taken. The 9th–11th rib section was removed from the left half carcass and then dissected into muscle, fat, and bones in order to estimate carcass composition. Gender had no effect (P > 0.05) on performance, intake, digestibility of dry matter and all the nutrients evaluated, feed efficiency, and carcass characteristics. It can be concluded that steers and heifers (spayed or not) have the same potential to produce beef. From a productive and welfare standpoint, there is no reason to spay heifers.     

Two-, three-, and four-breed rotational crossbreeding of beef cattle: carcass traits.

Carcass data from 1,494 straightbred and rotational crossbred steers were collected over four generations. Mating systems included straightbreds (Angus [A], Brahman [B], Charolais [C], and Hereford [H]); two-breed rotations (A-B, C-B, and H-B); three-breed rotations (A-B-C, A-B-H, and B-C-H); and a four-breed rotation (A-B-C-H). Steers were randomly allocated to one of four postweaning treatments that varied in length of grazing and feeding periods. Treatment and breed group (four straightbreds and seven rotational combinations) significantly influenced hot carcass weight (HCWT), retail yield (RY), longissimus muscle area (LM), fat thickness (FT), marbling score (MS), USDA quality grade (QG), and Warner-Bratzler shear force (WBS). Feeding for longer periods resulted in greater (P < .05) HCWT, RY, FT, and MS, higher QG, and lower (P < .05) WBS values. Among the straightbreds, C was heavier and larger for HCWT, RY, and LM (P < .01), whereas A and H had greater (P < .01) FT and MS. The B was similar to H for HCWT, RY, and LM and to C for FT but ranked last (P < .01) for MS and WBS. Three- and four-breed rotational mating systems were superior (P < .05) to the two-breed rotation for HCWT, RY, and LM but were similar for FT, MS, and WBS. Rotational combinations exceeded (P < .05) the straightbreds for all carcass traits except MS.     

Effects of aging on beef chuck and loin muscles enhanced with ammonium hydroxide and salt

The objective of this study was to determine whether aging would alter the beneficial effects (tenderness, juiciness, and flavor) of enhancing beef chuck and round steaks with a 20% solution of water, ammonium hydroxide, salt, and carbon monoxide. A randomized, complete block design was used, with 2 treatments [0% (control) and 20% (pump)], 3 aging periods (1, 2, and 3 wk), 3 muscles (M. triceps brachii from the clod heart, M. biceps femoris from the sirloin cap, and M. rectus femoris from the knuckle), and 3 replications. There were a total of 12 subprimals per treatment per aging period (n = 72 each). Individual steaks were cut to a thickness of 2.54 cm and packaged in a high-oxygen modified-atmosphere package (80% oxygen, 20% carbon dioxide). At the end of the aging period, steaks were vacuum packaged and frozen. Steaks were used to determine Warner-Bratzler shear force (WBS) and consumer sensory ratings. For all muscles, WBS values were lower for pump steaks than control at every aging period (P < 0.050). In addition, as aging period increased, WBS values for all steaks increased. Consumer taste panels revealed more desirability for tenderness, juiciness, flavor, and overall acceptability for pump steaks than control steaks. In addition, steaks aged for 1 d were more desirable than steaks aged for 7 and 14 d (P < 0.050). These data indicate that aging does not decrease the benefits (tenderness, juiciness, and flavor) of enhancement.     

Growth, carcass composition and plasma melatonin in postpubertal beef heifers fed melatonin

Two experiments were conducted to determine if feeding melatonin alters plasma concentrations of melatonin, growth and carcass composition of postpubertal beef heifers exposed to 16 h light (L):8 h dark (D). In Exp. 1, 16 heifers were blocked by initial body weight (318 +/- 5.6 kg). Four heifers were killed before starting the melatonin treatment to obtain initial carcass composition. Six heifers received vehicle (95% ethanol) and six were fed melatonin (4 mg/100 kg body weight) daily for 58 d at 1330 to coincide with the middle of the 16-h light period. On d 59 heifers were slaughtered. Melatonin feeding increased the percentage of fat in rib (P less than .05) and longissimus muscle (LD; P less than .10) and carcass fat accretion 28% (P less than .09) but reduced the percentage of protein 8% in rib (P less than .05) and carcass protein accretion 30% (P less than .09). Other measures in the carcass and body weight gain were not affected (P greater than .10) by feeding melatonin. Plasma concentrations of melatonin increased (P less than .01) from 10 to 140 pg/ml within 30 min of feeding melatonin. In Exp. 2, 24 heifers were blocked by initial body weight (348 +/- 13.7 kg). Eight heifers were killed initially, eight received vehicle and eight were fed melatonin for 63 d as described in Exp. 1. Melatonin did not influence (P greater than .10) body weight gain or any measure in the carcass; however, these heifers were fatter (40.1%) than those in Exp. 1 (30.9%) at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)