Analysis of DNA Methylation and mRNA Expression Level of MSTN Gene in Xinjiang Bashiby Sheep

In order to investigate DNA methylation and expression levels of myostatin (MSTN) gene in mscule and fat, 5 months of age of Bashiby sheep were selected, the promoter region and exon 1 methylation levels of MSTN gene was analyzed using bisulfite sequencing PCR (BSP). Real-time PCR was used to detect the expression level of MSTN gene in biceps femoris, femoral triceps, semitendinosus, semimembranosus, longissimus dorsi muscle and tail fat of Bashiby sheep. The results showed that the methylation probability of muscle was higher than fat, the methylation probability of biceps femoris, femoral triceps, semitendinosus, semimembranosus, longissimus dorsi muscle and tail fat were 74.2%, 74.2%, 83.2%, 83.7%, 82.1% and 25.3%, respectively. The expression levels of MSTN gene in biceps femoris, femoral triceps, semitendinosus, semimembranosus, longissimus dorsi muscle were significantly lower than tail fat in Bashiby sheep (P < 0.05), but there were no significant difference among biceps femoris, femoral triceps, semitendinosus, semimembranosus and longissimus dorsi muscle (P > 0.05).The DNA methylation was negatively correlated with the expression levels in muscle and fat of Bashiby sheep (r=-0.886, P < 0.05).     

新疆巴什拜羊肌肉生长抑制素基因DNA甲基化与mRNA表达量分析

为了探究肌肉生长抑制素（myostatin,MSTN）基因在肌肉和脂肪中的DNA甲基化模式及mRNA表达水平,试验以5月龄巴什拜羊羔羊为研究对象,采用亚硫酸氢盐测序法（bisulfite sequencing PCR,BSP）检测MSTN基因启动子区和第1外显子甲基化模式,并通过实时荧光定量PCR检测MSTN基因在巴什拜羊股二头肌、股三头肌、半腱肌、半膜肌、背最长肌和尾脂中的mRNA表达水平。结果显示,肌肉组织甲基化概率高于脂肪组织,其中,股二头肌、股三头肌、半腱肌、半膜肌、背最长肌和尾脂的甲基化概率分别为74.2%、74.2%、83.2%、83.7%、82.1%和25.3%,MSTN基因在股二头肌、股三头肌、半腱肌、半膜肌、背最长肌中的表达水平显著低于尾脂（P < 0.05）,股二头肌、股三头肌、半腱肌、半膜肌和背最长肌之间差异不显著（P > 0.05）,巴什拜羊肌肉和脂肪MSTN基因DNA甲基化水平与MSTN基因表达量呈显著负相关（r=－0.886,P < 0.05）。     

Variation in proteolysis, sarcomere length, collagen content, and tenderness among major pork muscles

The objectives of this experiment were to determine the extent of variation in proteolysis, sarcomere length, and collagen content among pork muscles and the association of those factors with tenderness variation among muscles at 1 d postmortem. Twenty-three white composite barrows were slaughtered and carcasses (66 kg) were chilled at 0 degrees C for 24 h. At 1 d postmortem, the longissimus lumborum, biceps femoris, semimembranosus, semitendinosus, and triceps brachii, long head were dissected from one side of each carcass and frozen. Trained sensory panelists evaluated tenderness, amount of connective tissue, juiciness, and pork flavor intensity of grilled (70 degrees C) chops on 8-point scales. Raw chops were used for total collagen content, sarcomere length, and the extent of desmin proteolysis. Tenderness ratings were highest (P < .05) for semitendinosus (7.2) and triceps brachii (7.1), followed by longissimus lumborum (6.4) and semimembranosus (5.7) and were lowest (P < .05) for biceps femorus (4.0). The simple correlations between longissimus lumborum tenderness and the tenderness of other muscles were .54 (semimembranosus), .34 (semitendinosus), .36 (triceps branchii), and .17 (biceps femorus). Total collagen was highest (P < .05) for biceps femorus (7.1 mg/g muscle), followed by triceps branchii (6.0 mg/g) and semitendinosus (5.3 mg/g), and lowest for semimembranosus (4.5 mg/g) and longissimus lumborum (4.1 mg/g). Sarcomere length was longest (P < .05) for semitendinosus (2.5 microm) and triceps branchii (2.4 microm), followed by semimembranosus (1.8 microm), longissimus lumborum (1.8 microm), and biceps femorus (1.7 microm). Proteolysis of desmin was greatest (P < .05) in longissimus lumborum (39.3%), followed by semimembranosus (21.0%) and biceps femoris (18.5%), then semitendinosus (.2%) and triceps brachii (.2%). Multiple linear regression using total collagen, sarcomere length, and proteolysis accounted for 57% of the variation in tenderness rating among all samples. Piecewise linear regression was used to account for the interaction of sarcomere length with proteolysis and collagen. This analysis accounted for 72% of the variation in tenderness rating. Variation in collagen, proteolysis, and sarcomere length and the degree of their interaction with one another determine the tenderness of individual muscles.     

Electrical stimulation effects on tenderness of five muscles from Hampshire x Rambouillet crossbred lambs with the callipyge phenotype

The objective of this study was to determine effects of electrical stimulation (ES) on muscle quality and sensory traits of 12 Hampshire x Rambouillet callipyge lambs. One side of each carcass was randomly assigned to an ES treatment of 550 V and 60 Hz of electricity for 2 s on and 2 s off 15 times. The other side was a nonstimulated control (NES). Heated calpastatin, sarcomere length, myofibrillar fragmentation index (MFI), Warner-Bratzler shear (WBS), and trained sensory panel values were measured on the semitendinosus (ST), semimembranosus (SM), longissimus (ML), supraspinatus (SP), and triceps brachii (TB) muscles. Electrically stimulating the carcass sides induced a more rapid (P = .001) pH decline in the longissimus muscle, and ES sides had a brighter (P = .001) red color of loineye than nonstimulated sides. At d 14 of storage (2 degrees C), the TB had the highest (P < .05) MFI value, indicating more protein degradation, and the ST and ML muscles had the lowest MFI (P = .008). Regardless of ES treatment, SM and ML had the highest (P < .05) WBS values. The ST muscle had higher (P < .05) WBS values than the SP but did not differ (P > .05) from the TB muscle. Electrical stimulation had no effect on WBS or any trained sensory panel values (P > .05). The percentage of loin chops rated slightly tender or better was improved 30 to 34% by electrical stimulation (P < .05). The ML muscle was scored lower (P < .05) in sustained juiciness compared with the SM, SP, and TB but did not differ (P > .05) from the ST muscle. The SM and ML muscles were rated lower (P < .05) in initial and sustained tenderness scores than other muscles. Tenderness scores were higher (P < .05) for the TB than for the SP but did not differ (P > .05) from the ST muscle. Electrically stimulating callipyge carcasses improves the tenderness of loin chops by increasing the percentage of chops rated from slightly tough to slightly tender.     

Relationships among glycolytic potential,dark cutting (dark,firm, and dry) beef,and cooked beef palatability

One hundred beef carcasses were selected at three packing plants and were used to determine the relationship between glycolytic potential (GP) and dark, firm, and dry (DFD) beef and to determine the effects of DFD status and GP on cooked beef palatability. Eight individual muscles were excised from one hindquarter of each carcass at d 7 postmortem: longissimus lumborum, psoas major, gluteus medius, tensor fasciae latae, rectus femoris, semimembranosus, biceps femoris, and semitendinosus. Ultimate pH, colorimeter readings, and Warner-Bratzler shear force were determined for all eight muscles at d 7 postmortem. A nine-member trained sensory panel evaluated cooked longissimus lumborum, gluteus medius, and semimembranosus steaks. Traits determined solely for the longissimus lumborum were GP (2 x [glycogen + glucose + glucose-6-phosphate] + lactate) and ether-extractable fat. A curvilinear relationship existed between GP and ultimate pH within the longissimus muscle. There appeared to be a GP threshold at approximately 100 micromol/g, below which lower GP was associated with higher ultimate pH and above which GP had no effect on ultimate pH. The greatest pH and muscle color differences between normal and DFD carcasses were observed in the longissimus lumborum, gluteus medius, semimembranosus, and semitendinosus muscles. Cooked longissimus from DFD carcasses had higher shear force values (46% greater) and more shear force variation (2.3 times greater variation) than those from normal carcasses. Dark cutting carcasses also had higher shear force values for gluteus medius (33% greater) and semimembranosus (36% greater) than normal carcasses. Sensory panel tenderness of longissimus, gluteus medius, and semimembranosus was lower for DFD carcasses than for normal carcasses. Longissimus and gluteus medius flavor desirability scores were lower for DFD than for normal carcasses. Steaks from DFD carcasses had more off-flavor comments than steaks from normal carcasses, specifically more "peanutty," "sour," and "bitter" flavors. The DFD effect of higher shear force values was approximately five times greater (+3.11 kg vs +0.63 kg) for carcasses with "slight" marbling scores than for carcasses with "small" marbling scores. In general, higher GP was associated with increased tenderness, even among normal carcasses. In conclusion, low GP was associated with DFD beef and resulted in substantially less-palatable cooked steaks.     

Increasing tenderness of beef round and sirloin muscles through prerigor skeletal separations

Crossbred steers (n = 30) were used to explore and compare tenderness improvements in beef round and sirloin muscles resulting from various methods of prerigor skeletal separations. Animals were slaughtered according to industry procedures, and at 60 min postmortem one of six treatments was applied to each side: A) control, B) saw pelvis at the sirloin-round junction, C) separate the pelvic-femur joint, D) saw femur at mid-point, E) combination of B and C, and F) combination of B and D. After 48 h, the following muscles were excised from each side: semimembranosus, biceps femoris, semitendinosus, and adductor from the round; vastus lateralis and rectus femoris from the knuckle; and gluteus medius, biceps femoris and psoas major from the sirloin. Following a 10-d aging period, samples were removed from each muscle to determine the effect of treatment on sarcomere length and Warner-Bratzler shear force. Most skeletal separation treatments resulted in longer sarcomeres than controls for semimembranosus, adductor, semitendinosus, and gluteus medius muscles. All skeletal separation treatments yielded shorter sarcomeres for the psoas major as compared with controls. Warner-Bratzler shear force differed among treatments for rectus femoris, semitendinosus, and psoas major. For rectus femoris, treatments C, D, E, and F resulted in lower (P < 0.05) shear values than for controls. Treatments B, D, and F increased shear force of the semitendinosus relative to controls (P < 0.05) within muscle. Treatment F resulted in higher shear force values for the PM than controls (P < 0.05). Correlations between sarcomere length and shear force were found to be low and quite variable among muscles. In general, treatments increased sarcomere length of several muscles from the sirloin/round region, but had mixed effects on shear force values.     

DLK1和MSTN基因在绵羊妊娠中后期胎儿中的表达分析

本研究以2个骨骼肌表型差异明显的特克塞尔和乌珠穆沁绵羊为试验对象,研究DLK1和MSTN基因在不同妊娠阶段胎儿不同部位骨骼肌中表达的调控机制及早期肌肉发育规律。在绵羊妊娠第85、100、120和135天时,对胎儿的半腱肌、半膜肌、背最长肌、股四头肌和股二头肌肌肉质量进行方差分析以及对DLK1和MSTN基因在5种骨骼肌中的表达量进行研究。结果表明,妊娠85天时特克塞尔羊的半膜肌、背最长肌、股四头肌和股二头肌质量显著或极显著(P<0.05或P<0.01)高于乌珠穆沁羊;妊娠100天时,5种骨骼肌组织生长发育在品种间的差异达到最大(P<0.05或P<0.01)。实时荧光定量分析表明,随着胎儿日龄的增加,DLK1基因在半腱肌、半膜肌、背最长肌、股四头肌和股二头肌骨骼肌中的表达量有增加的趋势,同时在特克塞尔羊中的表达量高于乌珠穆沁绵羊。在妊娠120天的半腱肌和半膜肌、妊娠100和135天的背最长肌、妊娠85天股四头肌和妊娠135天的股二头肌中DLK1表达量在2个品种间差异显著(P<0.05)。MSTN的表达量在特克塞尔羊中高于乌珠穆沁羊,但整体较低。妊娠135天时背最长肌和股四头肌中MSTN基因的表达量在2个品种间差异显著(P<0.05)。结果显示,DLK1和MSTN基因在不同日龄不同肌肉组织中的差异表达可能与肌肉早期发育有关。     

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.     

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.     

The Expression Comparison Analysis of FST and FMOD Genes in Sheep Fetus during Mid and Late Pregnancy

In order to investigate skeletal muscle development mechanism,the expression of follistatin (FST) and fibromodulin (FMOD) gene were comparatively analyzed in fetus different skeletal muscles and different stages between Ujumqin sheep and Texel sheep during early stage.Two gene expression were analyzed including longissimusdorsi,semimembranosus,semitendinosus quadricepsfemoris and biceps femoris muscle were compared by variance analysis methods of four stages (85,100,120 and 135 d).The results of quantitative Real-time PCR showed that the expression of FST gene showed a tendency to increase with the addition of stage,and the expression of FST gene in Texel sheep was higher than that in Ujumqin sheep in semitendinosus (100,120 d),semimembranosus (120 d),and biceps femoris (120 d) (P<0.05).The expression of FST gene in Texel sheep was extremly higher than that of Ujumqin sheep in semitendinosus (100,135 d),longissimusdorsi (85 d),quadricepsfemoris (100 d) and biceps femoris (100 d) (P<0.01).As a whole,the expression of FMOD gene was the highest in quadriceps femoris,and was lower in other four muscles,it's expression in Ujumqin sheep was higher than that in Texel sheep.It was inferred that FST and FMOD genes might be related to muscle development during early stage.     

FST和FMOD基因在绵羊胎儿妊娠中后期的表达特征比较

本研究以骨骼肌表型差异明显的两个绵羊品种特克塞尔羊和乌珠穆沁羊为试验对象,通过对两个与生长发育相关的基因卵泡抑素(follistatin,FST)与纤维蛋白聚糖基因(fibromodulin,FMOD)在不同日龄、不同骨骼肌部位表达的比较分析,探讨绵羊骨骼肌早期发育规律;同时对绵羊胎儿的85、100、120和135日龄4个阶段,在背最长肌、半腱肌、股四头肌、半膜肌和股二头肌5个部位肌肉FST和FMOD基因的表达量进行了比较研究。实时荧光定量PCR结果表明,随着胎儿日龄的增加,FST基因在半腱肌、股四头肌中表达量有增加的趋势,同时在特克塞尔绵羊中的表达量高于乌珠穆沁羊。在100和120日龄半腱肌、120日龄半膜肌、120日龄股二头肌中FST基因表达量在两个品种间差异显著(P<0.05),在100和135日龄半膜肌、85日龄背最长肌、100日龄股四头肌、100日龄股二头肌中FST基因表达量在两个品种间差异极显著(P<0.01)。FMOD基因在股四头肌中表达量较高,而在其他4种肌肉组织中相对表达量较低,且在乌珠穆沁羊中的表达量高于特克塞尔羊中的表达量。FST和FMOD基因在绵羊早期骨骼肌发育中起着重要作用。     

云岭牛不同解剖部位肉品质评价

为了明确云岭牛不同解剖部位肉的品质特性,本试验测定了云岭牛冈上肌（SU）、冈下肌（IF）、臀三头肌（TB）、菱形肌（RH）、颈腹侧锯肌（SVC）、夹肌（SP）,中部胴体的腰大肌（PM）、背最长肌（LD）、背阔肌（LA）,后部胴体的半膜肌（SM）、半腱肌（ST）、股二头肌（BF）、臀中肌（GM）、股直肌（RF）、股外侧肌（VL）和阔筋膜张肌（TFL）共16个解剖部位肉的压力失水率、蒸煮损失、剪切力、pH、亮度（L^*）、红度（a^*）、黄度（b^*）、粗蛋白质、脂肪、水分10项品质指标,并通过方差分析、相关性分析和标准化分析研究其品质特性。结果显示,云岭牛不同解剖部位肉之间的10项品质指标均存在显著差异（P<0.05）。冈上肌、冈下肌、腰大肌、颈腹侧锯肌和阔筋膜张肌的嫩度较好,其剪切力均低于4 kg。夹肌、半腱肌和股外侧肌的保水性较差,半腱肌的L^*值最高。相关性分析结果表明,剪切力和压力失水率、蒸煮损失呈显著正相关。标准化分析发现,背最长肌和半腱肌具有相似的品质特征;股二头肌、臀中肌和股外侧肌具有相似的品质特征。结果表明,部位因素对云岭牛肉品质具有显著影响,云岭牛胴体前部肉品质较好,可以作为开发高档产品的原料来源。     

Relationships between tropomyosin and myosin heavy chain isoforms in bovine skeletal muscle

The composition of tropomyosin (TPM) and myosin heavy chain (MyHC) isoforms was analyzed in 10 physiologically different bovine muscles ( masseter , diaphragm, tongue, semispinalis, pectoralis profundus , biceps femoris, psoas major , semimembranosus, longissimus thoracis and semitendinosus ) to clarify the relationships between TPM and MyHC isoforms in different muscle fiber types. The content of TPM1 and TPM3 was different in muscles according to their function in muscle contraction, although the content of TPM2 was constantly about 50% of the total TPM in all muscles. The content of TPM1 was higher in semimembranosus , longissimus thoracis and semitendinosus, while that of TPM3 was higher in masseter and diaphragm. The high positive correlation between MyHC-slow content and TPM3 content ( r  = 0.92) suggested a coexpression of TPM3 and MyHC-slow isoforms in a muscle fiber. MyHC-slow and TPM3 were expressed at the same level in masseter and diaphragm, whereas there was more TPM3 than MyHC-slow in tongue and semispinalis , so it appears that the excess TPM3 in tongue and semispinalis is expressed with other MyHC isoforms. MyHC-2a was the only fast type isoform expressed in tongue and semispinalis . Therefore, the excess TPM3 was composed of myofibrils with MyHC-2a. The results suggested that a fiber expressing MyHC-2a would be regulated delicately by changing the TPM isoform types.     

Variation in palatability and biochemical traits within and among eleven beef muscles

The objective of this study was to determine the extent of variation in, and relationships among, biochemical and palatability traits within and among 11 major beef muscles. Longissimus thoracis et lumborum (LD), psoas major (PM), gluteus medius (GM), semimembranosus (SM), adductor (AD), biceps femoris (BF), semitendinosus (ST), rectus femoris (RF), triceps brachii (TB), infraspinatus (IS), and supraspinatus (SS) from one side of 31 Charolais x MARC III steer carcasses were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, and then frozen at -30 degrees C. The 2.54-cm-thick steaks were obtained from two or three locations within muscles in order to assess biochemical traits and Warner-Bratzler shear force, and from near the center for sensory trait evaluation. The PM was most tender and was followed by IS in both shear force and tenderness rating (P < 0.05). The other muscles were not ranked the same by shear force and tenderness rating. The BF had the lowest (P < 0.05) tenderness rating. The PM, GM, and LD had lower (P < 0.05) collagen concentration (2.7 to 4.5 mg/g muscle) than muscles from the chuck and round (5.9 to 9.0 mg/g), except for the AD (4.9 mg/g). Desmin proteolysis was highest (P < 0.05) for BF and LD (60.7 and 60.1% degraded), and was lowest (P < 0.05) for PM (20.2%). The PM, TB, IS, RF, and ST had relatively long sarcomere lengths (> 2.1 microm), whereas the GM had the shortest (P < 0.05) sarcomere length (1.7 microm). Cooking loss was lowest (P < 0.05) for BF (18.7%) and was followed by LD and IS (20.7%); it was highest (P < 0.05) for ST (27.4%). Across all muscles, tenderness rating was highly correlated (r > 0.60) with shear force, connective tissue rating, sarcomere length, and collagen content. Within a muscle, correlations among all traits were generally highest in LD and lowest in AD. Within muscle, location effects were detected (P < 0.05) for shear force (PM, ST, BF, SM, and RF), sarcomere length (PM, ST, BF, LD, SS, IS, SM, and RF), collagen concentration (PM, BF, SS, IS, SM. AD, TB, and RF), desmin degradation (PM, GM, BF, SM, AD, and, RF), and cooking loss (all muscles except SS and AD). There is a large amount of variation within and among muscles for tenderness traits and tenderness-related biochemical traits. These results increase our understanding of the sources of variation in tenderness in different muscles and provide a basis for the development of muscle-specific strategies for improving the quality and value of muscles.     

The Quality Evaluation of Different Anatomical Locations of Yunling Cattle

In order to define the quality characteristics of different anatomical locations of Yunling cattle,the pressing loss rate,cooking loss rate,shear force,pH, L^* value,a^* value,b^* value,crude protein content,crude fat content and moisture of supraspinatus (SU),infraspinatus (IF),triceps brachii (TB),rhomboideus (RH),serratus ventraliscervicis (SVC),splenius (SP),psoas major (PM),longissimus dorsi (LD),latissimus dorsi (LA),semimembranosus (SM),semitendinosus (ST),biceps femoris (BF),gluteus medius (GM),rectusfemoris (RF),vastus lateralis (VL), tensor fasciae latae (TFL) from Yunling cattle carcass were determined.The quality traits of Yunling cattle meat among different anatomical locations were analyzed using variance,correlation and standardization analysis. The result showed that there were significant differences in quality traits among various anatomical locations (P<0.05). The SU,IF,PM,SVC and TFL had higher tenderness comparing to other muscles with shear force values less than 4 kg,while the water holding capacity of SP,ST and VL was poorer than other muscles. The ST had the highest L^* value among all muscles. There was significantly positive correlation between shear force and pressing loss, cooking loss rate. The LD and ST had similar quality characteristic,while BF,GM and VL had similar quality characteristic. It was showed that different parts of muscle had significant effect on Yunling cattle meat quality.The quality of forequarter meat was better, which could be used to develop high-end products.     

Adipocyte fatty acid-binding protein and mitochondrial enzyme activities in muscles as relevant indicators of marbling in cattle

Marbling is an important criterion for beef quality grading in many countries. The purpose of the current study was to utilize the natural genetic variation to identify major metabolic indicators of marbling in cattle differing in genotypes. Rectus abdominis (RA, oxidative), semitendinosus (glycolytic), and longissimus thoracis (LT, oxido-glycolytic) muscles were taken from steers of different genotypes that expressed high [Angus, n = 16; and crossbred (Angus x Japanese Black), n = 10] or low (Limousin, n = 12) levels of marbling in their meat. Muscles from Angus and crossbred steers were characterized, as expected, by a greater triacylglycerol (TAG) content (P < 0.001) and also by greater protein contents of fatty acid-binding protein specific for heart and muscles (H-FABP; P < 0.001 for RA and P < 0.05 for LT muscle) or for adipocytes (A-FABP; P < 0.001 for RA and LT muscles). Moreover, oxidative enzyme activities (beta-hydroxyacyl-CoA dehydrogenase, citrate synthase, isocitrate dehydrogenase, cytochrome-c oxidase) were greater (P < 0.01 to 0.001) in the 3 muscles studied, whereas glycolytic enzyme activities (phosphofructokinase and lactate dehydrogenase) were lower (P < 0.001) in RA muscle in Angus and crossbred steers compared with Limousin steers. Significant correlations were observed between TAG content and H- and A-FABP protein contents, and oxidative (r > or = +0.55, P < 0.001) or glycolytic enzyme activities (r > or = -0.47, P < 0.001), when the 3 genotypes and muscles studied were considered as a whole. In addition, A-FABP protein content and some oxidative enzyme activities were significantly correlated with TAG content independently of the genotype and muscle effects. In conclusion, A-FABP protein content, as well as oxidative enzyme activities, may be used as indicators of the ability of steers from extreme genotypes to deposit intramuscular fat.     

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 postmortem aging and USDA quality grade on Warner-Bratzler shear force values of seventeen individual beef muscles

Forty USDA Select and 40 upper two-thirds USDA Choice beef carcasses were used to determine the effects of postmortem aging on tenderness of 17 individual beef muscles. Biceps femoris-long head, complexus, gluteus medius, infraspinatus, longissimus dorsi, psoas major, rectus femoris, semimembranosus, semitendinosus, serratus ventralis, spinalis dorsi, supraspinatus, tensor fasciae latae, teres major, triceps brachii-long head, vastus lateralis, and vastus medialis muscles were removed from each carcass. Seven steaks (2.54-cm thick) were cut from every muscle, and each steak was assigned to one of the following postmortem aging periods: 2, 4, 6, 10, 14, 21, or 28 d postmortem. After completion of the designated aging period, steaks were removed from storage (2 degrees C, never frozen), cooked to a peak internal temperature of 71 degrees C, and evaluated using Warner-Bratzler shear force (WBSF). Analysis of WBSF revealed a 3-way interaction (P = 0.004) among individual muscle, USDA quality grade, and postmortem aging period. With the exception of the Select teres major, WBSF of all muscles (both quality grades) decreased with increasing time of postmortem storage. Nonlinear regression was used to characterize the extent (aging response) and rate of decrease in WBSF from 2 through 28 d postmortem for each muscle within each quality grade. In general, WBSF of upper two-thirds Choice muscles decreased more rapidly from 2 to 10 d postmortem than did corresponding Select muscles. Muscles that had greater aging responses generally had greater 2-d WBSF values. The upper two-thirds Choice psoas major, serratus ventralis, and vastus lateralis muscles required similar aging times to complete a majority of the aging response (< or =0.1 kg of aging response remaining) compared with analogous Select muscles. The upper two-thirds Choice complexus, gluteus medius, semitendinosus, triceps brachii-long head, and vastus medialis muscles required 4 to 6 d less time to complete a majority of the aging response than did comparable Select muscles. Aging times for Select biceps femoris-long head, infraspinatus, longissimus dorsi, rectus femoris, semimembranosus, spinalis dorsi, supraspinatus, and tensor fasciae latae muscles were > or =7 d longer than those for corresponding upper two-thirds Choice muscles. Results from this study suggest that muscle-to-muscle tenderness differences depend on quality grade and aging time and that postmortem aging should be managed with respect to individual muscle and USDA quality grade.     

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.