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.     

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.     

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.     

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。     

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.     

Mapping intramuscular tenderness variation in four major muscles of the beef round

The objective of this study was to quantify intramuscular tenderness variation within four muscles from the beef round: biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), and adductor (AD). At 48 h postmortem, the BF, ST, SM, and AD were dissected from either the left or right side of ten carcasses, vacuum packaged, and aged for an additional 8 d. Each muscle was then frozen and cut into 2.54-cm-thick steaks perpendicular to the long axis of the muscle. Steaks were broiled on electric broilers to an internal temperature of 71 degrees C. Location-specific cores were obtained from each cooked steak, and Warner-Bratzler shear force was evaluated. Definable intramuscular shear force variation (SD = 0.56 kg) was almost twice as large as between-animal shear force variation (SD = 0.29 kg) and 2.8 times as large as between-muscle variation (SD = 0.20 kg). The ranking of muscles from greatest to least definable intramuscular shear force variation was BF, SM, ST, and AD (SD = 1.09, 0.72, 0.29, and 0.15 kg, respectively). The BF had its lowest shear force values at the origin (sirloin end), intermediate shear force values at the insertion, and its highest shear force values in a middle region 7 to 10 cm posterior to the sirloin-round break point (P < 0.05). The BF had lower shear force values toward the ST side than toward the vastus lateralis side (P < 0.05). The ST had its lowest shear force values in a 10-cm region in the middle, and its highest shear force values toward each end (P < 0.05). The SM had its lowest shear force values in the first 10-cm from the ischial end (origin), and its highest shear force values in a 13-cm region at the insertion end (P < 0.05). Generally, shear force was lower toward the superficial (medial) side than toward the deep side of the SM (P < 0.05). There were no intramuscular differences in shear force values within the AD (P > 0.05). These data indicate that definable intramuscular tenderness variation is substantial and could be used to develop alternative fabrication and(or) merchandising methods for beef round muscles.     

Influence of zeranol implants and electrical stimulation on the palatability traits of five muscles in Angus and Limousin bulls and steers

A split-plot design was used to study effects of male status (bull vs steer), zeranol implants, breed types (Angus vs Limousin) and electrical stimulation on palatability traits of five major muscles when all animals were fed to a similar fat-thickness endpoint. Warner-Bratzler shear (WBS) determinations and taste-panel evaluations were performed on the longissimus, adductor, semimembranosus, semitendinosus and biceps femoris muscles removed 24 h postmortem. Breed was the most consistent main effect difference, with Angus cattle having lower WBS values than Limousin for the longissimus and semitendinosus muscles. Angus cattle also were favored in many sensory traits. Few significant differences were noted between bulls and steers in taste-panel traits. Differences due to electrical stimulation were most evident in the longissimus muscle, with higher panel-evaluation scores, an enhancement of marbling and lean color and a lower incidence of heat ring. The implant tended to have negative effects on palatability in this trial. An overall ranking of the five muscles based on WBS from most tender to least tender was: adductor, semimembranosus, longissimus, semitendinosus and biceps femoris. Correlations of palatability traits of one muscle to other muscles within an experimental unit were found to be low.     

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.     

Benchmarking carcass characteristics and muscles from commercially identified beef and dairy cull cow carcasses for Warner-Bratzler shear force and sensory attributes

The objective of this study was to benchmark carcasses and muscles from commercially identified fed (animals that were perceived to have been fed an increased plane of nutrition before slaughter) and nonfed cull beef and dairy cows and A-maturity, USDA Select steers, so that the muscles could be identified from cull cow carcasses that may be used to fill a void of intermediately priced beef steaks. Carcass characteristics were measured at 24 h postmortem for 75 carcasses from 5 populations consisting of cull beef cows commercially identified as fed (B-F, n = 15); cull beef cows commercially identified as nonfed (B-NF, n = 15); cull dairy cows commercially identified as fed (D-F, n = 15); cull dairy cows commercially identified as nonfed (D-NF, n = 15); and A-maturity, USDA Select grade steers (SEL, n = 15). Nine muscles were excised from each carcass [m. infraspinatus, m. triceps brachii (lateral and long heads), m. teres major, m. longissimus dorsi (also termed LM), m. psoas major, m. gluteus medius, m. rectus femoris, and m. tensor fasciae latae] and subjected to Warner-Bratzler shear force testing and objective sensory panel evaluation after 14 d of postmortem aging. Carcass characteristics differed (P < 0.05) among the 5 commercially identified slaughter groups for the traits of lean maturity, bone maturity, muscle score, HCW, fat color, subjective lean color, marbling, ribeye area, 12th-rib fat thickness, and preliminary yield grade. Carcasses from commercially identified, fed cull cows exhibited more (P < 0.01) weight in carcass lean than did commercially identified, nonfed cull cows. There was a group x muscle interaction (P = 0.02) for Warner-Bratzler shear force. Warner-Bratzler shear force and sensory overall tenderness values demonstrates that muscles from the SEL group were the most tender (P < 0.01), whereas muscles from the B-NF group were the least tender (P < 0.01). Sensory, beef flavor intensity was similar (P > 0.20) among cull cow carcass groups and more intense (P < 0.01) than the SEL carcass group. Muscles from the SEL group exhibited less (P < 0.01) detectable off-flavor than the cull cow carcass groups, whereas the B-NF group exhibited the most (P < 0.01) detectable off-flavor. Although carcass and muscle quality from commercially identified, fed, cull beef and dairy cows was not similar to A-maturity, USDA Select beef, they did show improvements when compared with nonfed, cull, beef and dairy cow carcasses and muscles.     

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.     

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.     

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.     

Relative contributions of animal and muscle effects to variation in beef lean color stability

Muscles from beef carcasses (n = 100) were selected from a commercial processor and aged for 14 d. Longissimus lumborum (LL), semimembranosus (SM), biceps femoris (BF), gluteus medius (GM), triceps brachii (TB), rectus femoris, vastus lateralis, adductor, semitendinosus, infraspinatus, teres major, biceps femoris ischiatic head, biceps femoris sirloin cap, and gracillus steaks were placed in display for 9 d. Instrumental color variables [lightness (L*), redness (a*), yellowness (b*), hue angle, chroma, and overall color change from d 0 (E)] were determined on d 0, 1, 3, 6, and 9 of display. Muscle pH and myoglobin content were determined for LL, SM, BF, GM, and TB. Muscles differed (P < 0.05) in initial values of each color variable evaluated, and the extent and timing of changes during display differed across muscles. Relationships between color variables measured in LL steaks and those measured in steaks from other muscles differed across days of display with the strongest relationships being observed earlier in the display period for labile muscles and later in stable muscles. Lightness of LL steaks was correlated with lightness of all of other muscles evaluated, regardless of display day (r = 0.27 to 0.79). For a*, hue angle, chroma, and E values, the strongest relationships between LL values and those of other muscles were detected between d 9 LL values and those of other muscles on d 3, 6, or 9, depending on the relative stability of the muscle. Correlation coefficients between d 9 a*, hue angle, chroma, and E values in LL and those of other muscles were 0.50, 0.65, 0.28, and 0.43 (P < 0.05) or greater, respectively, for the muscles included in the study. Myoglobin content of SM, BF, GM, and TB was highly correlated with that of LL (r = 0.83, 0.82, 0.72, and 0.67, respectively; P < 0.05). Muscle pH of LL was correlated with pH of SM and GM (r = 0.44 and 0.53; P < 0.05), but not (P > 0.05) pH of BF or TB. Muscle effects generally explained more variation in a*, b*, hue angle, chroma, and E than animal effects. However, the relative importance of animal effects increased as display continued. These data indicate that animal effects were consistent across muscles, though muscle effects had greater contribution to color stability variation. Furthermore, strong relationships between LL color stability and the stability of other muscles indicate that strategies developed to manage animal variation in LL color stability would beneficially affect the entire carcass.     

Specificity and reversibility of the training effects on the concentration of Na+,K+-Atpase in foal skeletal muscle

The purpose of the present study was to determine whether training and detraining affect the Na+,K+-ATPase concentration in horse skeletal muscles, and whether these effects are specific for the muscles involved in the training programme. Twenty-four Dutch Warmblood foals age 7 days were assigned randomly to 3 groups: Box (box-rest without training), Training (box-rest with training: short-sprint) and Pasture (pasture without training). Exercise regimens were carried out for 5 months and were followed by 6 months of detraining. Five of the foals in each group were subjected to euthanasia at age 5 months and the remaining foals at 11 months. Muscle samples were collected from the deep part of the gluteus medius, semitendinosus and masseter muscles. The Na+,K+-ATPase concentration was quantified by [3H]ouabain binding. In the Training group, the concentration of Na+,K+-ATPase in gluteus medius and semitendinosus muscle, but not in masseter muscle, showed a relative increase of 20% (P<0.05) as compared to Box foals. After detraining for the subsequent 6 months, the concentration of Na+,K+-ATPase in semitendinosus muscle remained the same, while that in gluteus medius muscle was reduced by 10%. It is concluded that: 1) short-sprint training for 5 months induced an increase of the Na+,K+-ATPase concentration in gluteus medius and semitendinosus muscles of the foal. Interestingly, this effect persisted during the 6 months of the detraining period. Whether the higher Na+,K+-ATPase concentration due to training of young foals leads to a better athletic performance when they become mature still needs to be established; 2) the factors that initiate an increase in Na+,K+-ATPase concentration following training are likely to be located in the muscle itself and 3) the training effect may last for several months after returning to normal activity, especially in muscles containing a high percentage of fast-twitch fibres.     

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。     

Recovering value from beef carcasses classified as dark cutters by United States Department of Agriculture graders

Effects of the dark-cutting condition were examined on commercially slaughtered beef carcass sides that were classified into groups exhibiting 1/3, 1/2, and full degrees of the dark-cutting (DEGDC) condition, as evaluated by a USDA-Agricultural Marketing Service grader (n = 20 per group). Twenty-nine muscles of each carcass side were evaluated to determine the ultimate pH and color (L*, a*, and b*). Fourteen beef muscles (biceps femoris, deep pectoral, chuck complexus, gluteus medius, infraspinatus, latissimus dorsi, psoas major, longissimus thoracis, longissimus lumborum, semimembranosus, semitendinosus, triceps brachii long head, tensor fasciae latae, and vastus lateralis) were evaluated using Warner-Bratzler Shear force (WBSF) and a trained sensory panel. The muscle x DEGDC interaction was significant for ultimate pH, L*, a*, and b* values (P < 0.05). When ultimate pH values of individual muscles were compared with the same muscles evaluated in a previous study, the 1/3, 1/2, and full DEGDC had 7, 9, and 5 muscles, respectively, that fell within a computed 95% prediction limit of what would be considered as a normal pH but were more variable as measured by within-class CV. Color values (L*, a*, and b*) of the muscles from dark-cutting carcasses were numerically lower than those from the normal carcasses. A survey designed to determine the ideal color range of beef lean for retail meat merchandisers (n = 34) and food service chefs (n = 33) across the United States resulted in data analyzed using principal components analysis of L*, a*, and b* values for muscles dissected in the study to estimate the true values for dark-cutting carcasses. Muscles that were within an acceptable color value range for food service chefs had the potential to add between $42.29 to $26.44 and $14.71 to $8.11 per side when valued at Choice and Select prices, respectively. Muscles that were within an acceptable color value range had the potential to add between $30.39 to $16.74 and $10.37 to $5.03 per side for retail meat merchandisers when acceptable muscles were valued at Choice and Select prices, respectively. No muscle x DEGDC interactions were detected for WBSF and sensory panel scores (P > 0.05), but differences were detected among muscles (P < 0.05). Several muscles were considered salvageable from the dark-cutting carcasses that were evaluated, and no significant differences in sensory scores or WBSF between DEGDC classes suggested equal sensory expectations for muscles from dark-cutting carcasses.     

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。     

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%.