Muscle Sarcomere Length Research Articles

Influence of age at slaughter and sex on carcass characteristics, meat quality, fatty acids, and ribonucleotides in white-tailed yellow native chickens.

This study investigated the effects of age and sex on carcass and meat characteristics of one of Thailand's major indigenous chicken breeds, the white-tailed yellow native chicken (NC). A total of 120 one-day-old NC (60 males and 60 females) were raised, and harvested at either 16, 20 or 24 weeks. The results showed that body, carcass, breast and fillet weights did not differ (P > 0.05) between 16- and 20-week-old NC, but were lower (P < 0.05) than those of 24-week-old NC. Male NC had higher (P < 0.05) body, carcass, wing, back and thigh weights than female NC. Neither sex nor age affected muscle pH, sarcomere length, redness and yellowness, guanosine monophosphate, and hypoxanthine. The interaction between age and sex was significant (P < 0.05) for %dressing, %leg, L*, C14:1, C18:1n9 and C20:4n6. Shear force was lower in 16-week-old NC (P < 0.05). The 24-week-old NC had lower (P < 0.05) C13:0, C16:0, C18:0, C18:2n6t, C20:4n6, C22:6n-3, intramuscular fat and inosine 5'-monophosphate levels and higher (P < 0.05) C18:2n6c, C18:3n-3 and C20:3n-6 levels than the 16- and 20-week-old NC. Male NC had higher (P < 0.05) C13:0-, C14:0-, C18:2n6t-, C20:3n-6- and lower inosine levels than female NC. In conclusion, these data highlight age- and sex-specific differences in carcass and meat quality of NC and provide relevant information to support consumer-oriented decisions on the production, processing and nutritional value of NC.

Multiscale hamstring muscle adaptations following 9 weeks of eccentric training.

Eccentric training, such as Nordic hamstring exercise (NHE) training, is commonly used as a preventive measure for hamstring strains. Eccentric training is believed to induce lengthening of muscle fascicles and to be associated with the addition of sarcomeres in series within muscle fibers. However, the difficulty in measuring sarcomere adaptation in human muscles has severely limited information about the precise mechanisms of adaptation. This study addressed this limitation by measuring the multiscale hamstring muscle adaptations in response to 9 weeks of NHE training and 3 weeks of detraining. Twelve participants completed 9 weeks of supervised NHE training, followed by a 3-week detraining period. We assessed biceps femoris long-head (BFlh) muscle fascicle length, sarcomere length, and serial sarcomere number in the central and distal regions of the muscle. Additionally, we measured muscle volume and eccentric strength at baseline, post-training, and post-detraining. NHE training over 9 weeks induced significant architectural and strength adaptations in the BFlh muscle. Fascicle length increased by 19% in the central muscle region and 33% in the distal muscle region. NHE also induced increases in serial sarcomere number (25% in the central region and 49% in the distal region). BFlh muscle volume increased by 8%, and knee flexion strength increased by 40% with training. Following 3 weeks of detraining, fascicle length decreased by 12% in the central region and 16% in the distal region along with reductions in serial sarcomere number. Nine weeks of NHE training produced substantial, region-specific increases in BFlh muscle fascicle length, muscle volume, and force generation. The direct measurement of sarcomere lengths revealed that the increased fascicle length was accompanied by the addition of sarcomeres in series within the muscle fascicles.

The carcass characteristics and quality of meat from lambs grazing perennial wheat with different companion legumes (clover, serradella, lucerne) or a mineral supplement

This study compared carcasses as well as the quality and mineral concentration of meat from lambs extensively grazing perennial wheat with clover (PW + C), serradella (PW + S), lucerne (PW + L), or a mineral salt supplement (PW + Min). A split-plot design was used, wherein 3 crossbred ewe lambs (n = 72 in total) (sub-plots) grazed each of 4 forage types (plots), that were replicated across 6 locations (blocks). The feeding study concluded after 96 d, when all the lambs were slaughtered. The left longissimus lumborum muscles (LL) were collected and wet aged for either 5 or 56 d post-mortem. Lambs grazing PW + Min were found to produce carcasses with lower dressing percentage values to those grazing the other forage types (P = 0.037). The LL of lambs grazing PW + L had the lowest crude protein values (P = 0.015). Forage type by ageing period interactions did not affect meat quality. The 56 d ageing period resulted in higher purge loss (P < 0.001) and TVB-N values (P < 0.001) and a decline in shear force (P < 0.001) compared to the 5 d ageing period. The other carcass and meat quality parameters were not affected by forage type; including hot carcass weight, pH decline parameters, eye muscle area, cooking loss, intramuscular fat, sarcomere length, colour stability, and concentrations of calcium, iron, magnesium, sodium, and zinc in the LL. These findings confirm that perennial cereal production systems, that include legume forages with contrasting protein, energy, and micronutrient profiles, can deliver comparable lamb carcasses and meat quality.

An Effective Glucagon-Like Peptide-1 Receptor Agonists, Semaglutide, Improves Sarcopenic Obesity in Obese Mice by Modulating Skeletal Muscle Metabolism.

PurposeThis study aimed to investigate the effect of Semaglutide on skeletal muscle and its metabolomics.MethodsA total of 18 male C57BL/6 mice were randomly divided into normal control (NC) group, high-fat diet (HFD) group and HFD+Semaglutide group, and were given standard diet, HFD diet, HFD diet plus Semaglutide, respectively. The body weight, gastrocnemius weight, serum lipid, blood glucose and inflammatory index levels of mice in each group were observed and compared, and the morphological and structural changes of gastrocnemius were also analyzed. Meanwhile, gastrocnemius metabolite changes were analyzed by untargeted metabolomics.ResultsAfter Semaglutide treatment, the food intake and body weight of mice were evidently decreased, while the relative gastrocnemius weight ratio were conversely increased. Meanwhile, the levels of TG, CHO, LDL, HDL, TNF-α, IL-6, IL-1β and HOMA-IR were all observed to decrease remarkably after Semaglutide intervention. Histological analysis showed that Semaglutide significantly improved the pathological changes of gastrocnemius, manifested as increased type I/type II muscle fiber ratio, total muscle fiber area, muscle fiber density, sarcomere length, mitochondrial number and mitochondrial area. Furthermore, metabolic changes of gastrocnemius after Semaglutide intervention were analyzed, and 141 kinds of differential metabolites were screened out, mainly embodied in lipids and organic acids, and enriched in 9 metabolic pathways including a variety of amino acids.ConclusionSemaglutide can significantly reduce the body weight and the accumulation of intramuscular fat, promote muscle protein synthesis, increase the relative proportion of skeletal muscle, and improve muscle function of obese mice, possibly by altering the metabolism of muscle lipids and organic acids.

Structure-Function Relationships in Muscle Fibres: MyoRobot Online Assessment of Muscle Fibre Elasticity and Sarcomere Length Distributions.

Muscle biomechanics is set by the spacing of repetitive striation patterns of individual sarcomeres within single muscle fibres of stacked myofibrils. Sarcomere lengths (SL) are rather unequally distributed than of equal distance. This non-uniformity may affect both, force production as well as passive-elastic deformation. However, online recording of SL during axially imposed strains is cumbersome due to a lack of compact technologies. To fuse SL pattern recognition with restoration force assessments during quasi-static axial stretch, we implemented live tracking of SL distributions simultaneous to voice-coil actuated stretch and restoration force recordings in our MyoRobot 2.0 automated biomechatronics platform. Both were obtained online during stretch-relaxation cycles of murine single muscle fibres. Under quasi-static stretch conditions ( ∼1 μm/s fibre length changes), almost no apparent hysteresis was detected in single fibres. SL showed a non-uniform distribution. While mean SL varied between 2.6 μm and 3.4 μm upon 140% stretch, two populations of fibres were noticed: one showing a minor change in SL distribution with stretch, and one becoming more equally distributed upon stretch. A roughly 5% SL variability under rest either diminishes or remains almost unaltered upon elastic axial deformation. This may reflect differential impact of mostly extra-sarcomeric components to stretch in this stretch range. The augmented functionality of the MyoRobot 2.0 towards online sarcomere analyses within single fibres shall provide a valuable tool for the muscle community to study the contribution of serial elastic and force producing elements in health and disease models.

The muscle M3 x-ray diffraction peak and sarcomere length: No evidence for disordered myosin heads out of actin overlap.

X-ray diffraction studies of muscle have provided a wealth of information on muscle structure and physiology, and the meridian of the diffraction pattern is particularly informative. Reconditi et al. (2014. J. Physiol.https://doi.org/10.1113/jphysiol.2013.267849) performed superb experiments on changes to the M3 meridional peak as a function of sarcomere length (SL). They found that the M3 intensity dropped almost linearly as sarcomere length increased at least to about SL = 3.0 µm, and that it followed the same track as tension, pointing toward zero at the end of overlap at ∼3.6 µm. They concluded that, just as tension could only be generated by overlapped myosin heads, so ordered myosin heads contributing to the M3 intensity could only occur in the overlap region of the A-band, and that nonoverlapped heads must be highly disordered. Here we show that this conclusion is not consistent with x-ray diffraction theory; it would not explain their observations. We discuss one possible reason for the change in M3 intensity with increasing sarcomere length in terms of increasing axial misalignment of the myosin filaments that at longer sarcomere lengths is limited by the elastic stretching of the M-band and titin.

Influence of muscle type and microstructure on iridescence in cooked, cured pork meat products.

Microstructural factors associated with surface iridescence in cooked, cured pork products were investigated. Meat iridescence is a commonly observed physical phenomenon in raw meat and meat products that consist of intact muscle tissue. Since the purchase decision of consumers is mainly driven by the first impression of meat color and appearance, products showing colorful iridescence may be rejected. Four different muscles (RF: M. rectus femoris, BF: M. biceps femoris, ST: M. semitendinosus, and LD: M. longissimus thoracis et lumborum) were brine-injected, cooked, sliced, and iridescence was evaluated by digital image analysis and sensory analysis. Sarcomere lengths, fiber diameters, and surface microstructure were analyzed in iridescent and noniridescent sections. Highest iridescence extent by image analysis was found in LD (37.3± 16.4%), and highest overall iridescence score (extent and intensity, 6.11± 1.78) was observed in BF. Sarcomere lengths did not differ significantly between iridescent (1.05± 0.09µm LD) and noniridescent areas (1.08± 0.94µm LD) within muscles (p>0.05). Iridescent sections showed smooth and ordered surface structures with cross-sectioned myofibers, whereas in noniridescent sections, surfaces were more unstructured and myofibers obliquely cut. The results of the study indicate that the sarcomere length and fiber diameters may thus be only of minor importance for the explanation of meat iridescence in cooked meat products and are rather related to multiple scattering and absorption effects on smaller structural entities such as the myofilament lattice or larger entities such as fiber bundles. PRACTICAL APPLICATION: Iridescence can be a problem for the meat industry due to consumers concerns about green-iridescent colors in meat. The underlying mechanisms and structures have not yet been fully clarified, and thus no practical solutions to eliminate iridescence have been found so far. This research presents new insights into the structural attributes that are interrelated with meat iridescence and shows that iridescence is rather influenced by cutting angle of muscle fibers and surface homogeneity than by muscle fiber diameters or sarcomere lengths. This should be considered by the industry when seeking for ways to reduce the potential problem of iridescence.

The cibarial pump of the xylem-feeding froghopper Philaenus spumarius produces negative pressures exceeding 1 MPa.

The xylem sap of vascular plants is an unlikely source of nutrition, being both nutrient poor and held under tensions (negative pressures) that can exceed 1 MPa. But some insects feed on xylem sap exclusively, extracting copious quantities using a muscular cibarial pump. However, neither the strength of the insect's suction, nor the direct energetic cost of xylem ingestion, have ever been quantified. Philaenus spumarius froghoppers were used to address these gaps in our knowledge. Micro-CT scans of its cibarium and measurements of cibarial muscle sarcomere length revealed that P. spumarius can generate a maximum tension of 1.3 ± 0.2 MPa within its cibarium. The energetic cost of xylem extraction was quantified using respirometry to measure the metabolic rate (MR) of P. spumarius while they fed on hydroponically grown legumes, while xylem sap excretion rate and cibarial pumping frequency were simultaneously recorded. Increasing the plants' xylem tensions up to 1.1 MPa by exposing their roots to polyethylene glycol did not reduce the insects' rate of xylem excretion, but significantly increased both MR and pumping frequency. We conclude that P. spumarius can gain energy feeding on xylem sap containing previously reported energy densities and at xylem tensions up to their maximum suction capacity.

Effects of maternal dietary energy restriction on breast muscle fibre development in the offspring of broiler breeders.

ObjectiveThe effects of maternal dietary energy levels on breast muscle fibre development in offspring of broiler breeders were investigated.MethodsA total of 480 20-week-old Arbor Acres (AA) healthy female broiler breeders, with an average body weight of 2.33±0.01 kg, were randomly divided into 4 treatment groups with 6 replicates and 20 broiler breeders for each replicate and fed a corn and soybean meal diet with 100%, 80%, 70%, and 50% energy levels, respectively. Approximately 300 eggs per treatment were collected for incubation for 6 days. Then, 120 0-day-old female broilers at each energy level were randomly selected and divided into 6 replicates with 20 broilers for each replicate, with this experimental phase with the offspring lasting for 49 days.ResultsCompared with the 100% energy group, the breast muscle fibre diameter at embryonic day 21 in the 80% energy group was significantly reduced (p<0.05). In the 80% energy group, the muscle fibre density of the breast increased significantly (p<0.05) at embryonic days 15 and 21. The breast muscle fibre diameter of the offspring in each group was significantly decreased (p<0.05) on the 1st day. The breast muscle sarcomere length of the embryos in the 80% energy group was significantly higher (p<0.05) than those in the 70% and 50% energy groups. Compared with the 100% energy group, the expression of the myostatin gene in the offspring was significantly decreased (p<0.05).ConclusionIn conclusion, the effects of a maternal dietary energy level of 80% in this study were found to be optimal for breast muscle fibre development in offspring, which indicated that the metabolic energy level of AA broilers of 9.36 MJ/kg for the mid-term diet for laying eggs has a more practical significance.

Changes in Muscle Stress and Sarcomere Adaptation in Mice Following Ischemic Stroke.

While abnormal muscle tone has been observed in people with stroke, how these changes in muscle tension affect sarcomere morphology remains unclear. The purpose of this study was to examine time-course changes in passive muscle fiber tension and sarcomeric adaptation to these changes post-ischemic stroke in a mouse model by using a novel in-vivo force microscope. Twenty-one mice were evenly divided into three groups based on the time point of testing: 3 days (D3), 10 days (D10), and 20 days (D20) following right middle cerebral artery ligation. At each testing time, the muscle length, width, and estimated volume of the isolated soleus muscle were recorded, subsequently followed by in-vivo muscle tension and sarcomere length measurement. The mass of the soleus muscle was measured at the end of testing to calculate muscle density. Two-way ANOVA with repeated measures was used to examine the differences in each of the dependent variable among the three time-point groups and between the two legs. The passive muscle stress of the impaired limbs in the D3 group (27.65 ± 8.37 kPa) was significantly lower than the less involved limbs (42.03 ± 18.61 kPa; p = 0.05) and the impaired limbs of the D10 (48.92 ± 14.73; p = 0.03) and D20 (53.28 ± 20.54 kPa; p = 0.01) groups. The soleus muscle density of the impaired limbs in the D3 group (0.69 ± 0.12 g/cm3) was significantly lower than the less involved limbs (0.80 ± 0.09 g/cm3; p = 0.04) and the impaired limbs of the D10 (0.87 ± 0.12 g/cm3; p = 0.02) and D20 (1.00 ± 0.14 g/cm3; p < 0.01) groups. The D3 group had a shorter sarcomere length (2.55 ± 0.26 μm) than the D10 (2.83 ± 0.20 μm; p = 0.03) and D20 group (2.81 ± 0.15 μm; p = 0.04). These results suggest that, while ischemic stroke may cause considerable changes in muscle tension and stress, sarcomere additions under increased mechanical loadings may be absent or disrupted post-stroke, which may contribute to muscle spasticity and/or joint contracture commonly observed in patients following stroke.

360 Awardee Talk: The evolution of meat flavor measurement and its importance to the livestock industry

Abstract Meat flavor is part of the trilogy of traits that determine taste: tenderness, juiciness, and flavor. For meat, juiciness is influenced by the amount of intramuscular fat and moisture that is retained during the cooking process. Meat tenderness is primarily determined by the amount and type of connective tissue, degree of protein degradation, and muscle sarcomere length. Tenderness has been managed genetically in livestock, with significant strides being made to reduce the number of steaks rated tough. The last factor that influences consumers’ perception of meat taste is flavor and aroma. Compared to juiciness and tenderness, flavor is much more complex, as it is influenced by lipids and water-soluble compounds that serve as precursors to meat flavor. These precursors are then developed into flavor and aromas during the cooking process. Flavor is measured by consumers via sensing on the tongue, trigeminal senses, and volatile aroma compounds and is largely variable from one consumer to the next. Objectively measuring flavor is much more complicated than either juiciness or tenderness and requires either a highly-trained human sensory panel or expensive, highly-sensitive equipment. The development of the beef flavor lexicon in 2011 provided a comprehensive list of beef flavor descriptors with objective references for each and anchors along a scale of 0 to 15, allowing a trained sensory panel to objectively measure and score the flavor descriptors. Gas and liquid chromatography coupled with mass spectroscopy objectively measure volatile aroma compounds and flavor precursors, respectively. Now the use of “omics” techniques have been adapted to flavor research to help relate protein, lipids, and other metabolites with flavor characteristics. Meat flavor is what most appeals to consumers and sets it apart from plant proteins. Furthermore, flavor serves as the guardrails to keep a premium marketability on track and is something that the livestock industry has that makes their product unique and desirable.

The combined effects of ocean acidification and warming on a habitat-forming shell-crushing predatory crab

In mid rocky intertidal habitats the mussel Perumytilus purpurarus monopolizes the substratum to the detriment of many other species. However, the consumption of mussels by the shell-crushing crab Acanthocyclus hassleri creates within the mussel beds space and habitat for several other species. This crab uses its disproportionately large claw to crush its shelled prey and plays an important role in maintaining species biodiversity. This study evaluated the consequences of projected near-future ocean acidification (OA) and warming (OW) on traits of A. hassleri linked with their predatory performance. Individual A. hassleri were maintained for 10–16 weeks under contrasting pCO2 (~500 and 1400 μatm) and temperature (~15 and 20 °C) levels. We compared traits at the organismal (oxygen consumption rate, survival, calcification rate, feeding rates, crusher claw pinching strength, self-righting speed, sarcomere length of the crusher claw muscles) and cellular (nutritional status ATP provisioning capacity through citrate synthase activity, expression of HSP70) level. Survival, calcification rate and sarcomere length were not affected by OA and OW. However, OW increased significantly feeding and oxygen consumption. Pinching strength was reduced by OA; meanwhile self-righting was increased by OA and OW. At 20 °C, carbohydrate content was reduced significantly by OA. Regardless of temperature, a significant reduction in energy reserves in terms of protein content by OA was found. The ATP provisioning capacity was significantly affected by the interaction between temperature and pCO2 and was highest at 15 °C and present day pCO2 levels. The HSP70 levels of crabs exposed to OW were higher than in the control crabs. We conclude that OA and OW might affect the amount and size of prey consumed by this crab. Therefore, by reducing the crab feeding performance these stressors might pose limits on their role in generating microhabitat for other rocky intertidal species inhabiting within mussel beds.

Preganglionic and Postganglionic Brachial Plexus Birth Injury Effects on Shoulder Muscle Growth

Brachial plexus birth injury can differ in presentation, depending on whether the nerve ruptures distal to, or avulses proximal to, the dorsal root ganglion. More substantial contracture and bone deformity at the shoulder is typical in postganglionic injuries. However, changes to the underlying muscle structure that drive these differences in presentation are unclear. Seventeen Sprague-Dawley rats received preganglionic or postganglionic neurectomy on a single limb on postnatal days 3 and 4. Muscles crossing the shoulder were retrieved once the rats were sacrificed at 8 weeks after birth. External rotation range of motion, muscle mass, muscle length, muscle sarcomere length, and calculated optimal muscle length were measured bilaterally. Average shoulder range of motion in the postganglionic group was 61.8% and 56.2% more restricted at 4 and 8 weeks, respectively, compared with that in the preganglionic group, but affected muscles after preganglionic injury were altered more severely (compared with the unaffected limb) than after postganglionic injury. Optimal muscle length in preganglionic injury was shorter in the affected limb (compared with the unaffected limb: -18.2% ± 9.2%) and to a greater extent than in postganglionic injury (-5.1% ± 6.2%). Muscle mass in preganglionic injury was lower in the affected limb (relative to the unaffected limb: -57.2% ± 24.1%) and to a greater extent than in postganglionic injury (-28.1% ± 17.7%). The findings suggest that the presence of contracture does not derive from restricted longitudinal muscle growth alone, but also depends on the extent of muscle mass loss occurring simultaneously after the injury. This study expands our understanding of differences in muscle architecture and the role of muscle structure in contracture formation for preganglionic and postganglionic brachial plexus birth injury.

WITHDRAWN: Beef tenderness evaluation using early post-mortem muscle nanostructure.

Ahead of Print article withdrawn by publisher.

Modelling force-length-activation relationships of wrist and finger extensor muscles.

The wrist and finger extensors play a crucial role in the muscle coordination during grasping tasks. Nevertheless, few data are available regarding their force-generating capacities. The objective of this study was to provide a model of the force-length-activation relationships of the hand extensors using non-invasive methods. The extensor carpi radialis (ECR) and the extensor digitorum communis (EDC) were studied as representative of wrist and finger extensors. Ten participants performed isometric extension force-varying contractions in different postures on an ergometer recording resultant moment. The joint angle, the myotendinous junction displacement and activation were synchronously tracked using motion capture, ultrasound and electromyography. Muscle force was estimated via a musculoskeletal model using the measured joint angle and moment. The force-length-activation relationship was then obtained by fitting a force-length model at different activation levels to the measured data. The obtained relationships agreed with previously reported data regarding muscle architecture, sarcomere length and activation-dependent shift of optimal length. Muscle forces estimated from kinematics and electromyography using the force-length-activation relationships were comparable, below 15% differences, to those estimated from moment via the musculoskeletal model. The obtained quantitative data provides a new insight into the different muscle mechanics of finger and wrist extensors. Graphical abstract By combining in vivo data (kinematics, dynamometry, electromyography, ultrasonography) during isometric force-varying contractions with musculoskeletal modelling, the force-length-activation relationships of both finger and wrist extensors were obtained. The results provided a new insight into the role of hand extensors in the generation and control of hand movements.

Exploring the Factors Contributing to the High Ultimate pH of Broiler Pectoralis Major Muscles Affected by Wooden Breast Condition.

The elevated ultimate pH (pHu) found in wooden breast (WB) meat suggests an altered muscular energetic status in WB but also could be related to a prematurely terminated post-mortem pH decline. The aims of this study were to explore the factors contributing to the elevated pHu and establish whether the occurrence of WB defect alters muscle post-mortem carbohydrate metabolism and determine if the contractile apparatus reflects such changes. A total of 24 carcasses from Ross 308 male chickens were obtained from a commercial producer and harvested using commercial processing procedures. Carcasses were categorized into unaffected (NORM) and WB groups (n = 12 each), and samples were collected from cranial bone-in pectoralis major (PM) muscles at 15 min and 24 h post-mortem for the determination of pH, glycolytic metabolites, adenonucleotides, buffering capacity, phosphofructokinase (PFK) activity, and in vitro pH decline. Twenty-four additional deboned PM samples (12 NORM and 12 WB) were collected from the same processing plant to assess muscle histology and sarcomere length at four different locations throughout the PM muscle. Data show that the reduced glycolytic potential of WB muscles only partially explains the higher (P < 0.001) pHu of WB meat, as residual glycogen along with unaltered PFK activity suggests that neither glycogen nor a deficiency of PFK is responsible for arresting glycolysis prematurely. The dramatic reduction in ATP concentrations in the early post-mortem period suggests a defective ATP-generating pathway that might be responsible for the reduced pH decline in WB samples. Further, the addition of excess of ATPase extended post-mortem glycolysis of WB meat in an in vitro glycolytic system. WB-affected samples have longer (P < 0.001) sarcomeres compared to NORM, indicating the existence of compromised energy-generating pathways in myopathic muscles that may have had consequences on the muscle contraction and tension development, as in vivo, also during the post-mortem period. Considering the overall reduced glycolytic potential and the myodegenerative processes associated with WB condition, we speculate that the higher pHu of WB meat might be the outcome of a drastically impaired energy-generating pathway combined with a deficiency and/or a dysfunction of muscle ATPases, having consequences also on muscle fiber contraction degree.

Architecture of the Short External Rotator Muscles of the Hip

BackgroundMuscle architecture, or the arrangement of sarcomeres and fibers within muscles, defines functional capacity. There are limited data that provide an understanding of hip short external rotator muscle architecture. The purpose of this study was thus to characterize the architecture of these small hip muscles.MethodsEight muscles from 10 independent human cadaver hips were used in this study (n = 80 muscles). Architectural measurements were made on pectineus, piriformis, gemelli, obturators, quadratus femoris, and gluteus minimus. Muscle mass, fiber length, sarcomere length, and pennation angle were used to calculate the normalized muscle fiber length, which defines excursion, and physiological cross-sectional area (PCSA), which defines force-producing capacity.ResultsGluteus minimus had the largest PCSA (8.29 cm2) followed by obturator externus (4.54 cm2), whereas superior gemellus had the smallest PCSA (0.68 cm2). Fiber lengths clustered into long (pectineus - 10.38 cm and gluteus minimus - 10.30 cm), moderate (obturator internus - 8.77 cm and externus - 8.04 cm), or short (inferior gemellus - 5.64 and superior gemellus - 4.85). There were no significant differences among muscles in pennation angle which were all nearly zero. When the gemelli and obturators were considered as a single functional unit, their collective PCSA (10.00 cm2) exceeded that of gluteus minimus as a substantial force-producing group.ConclusionsThe key findings are that these muscles have relatively small individual PCSAs, short fiber lengths, and low pennation angles. The large collective PCSA and short fiber lengths of the gemelli and obturators suggest that they primarily play a stabilizing role rather than a joint rotating role.

Performance and body composition of young Nellore bulls slaughtered at different body weights

The objective of this work was to evaluate the effect of slaughter body weight on the quantitative characteristics of carcasses and the yield of commercial cuts of young Nellore bulls. Twenty-four non-castrated, 11-month-old, feedlot-fed Nellore bulls were distributed in a completely randomized design, in three treatments: 350 kg, 400 kg or 450 kg of body weight at slaughter (SBW). Slaughter was performed in a commercial slaughterhouse. The data were analyzed by an ANOVA followed by a Tukey test (p ? 0.05). SBW had no relationship with dry matter intake (6.05 kg/day or 75.74 g/kg BW0.75), feed efficiency (22.16) or feed conversion (4.67). Average daily gain was different depending on the SBW. Animal slaughtered at 350 kg had gained 1.17 kg/day, whereas animals slaughtered at 400 and 450 kg had gained 1.49 and 1.47 kg/day, respectively. Cold carcass weight increased with SBW (189.50, 209.33, and 242.39, respectively). Other carcass characteristics, like pH at 48 h (5.75), cold dressing carcass (52.61%), chilling losses (1.79%), fat thickness (5.54 mm), marbling (3.34 points), intramuscular fat (6.68%), longissimus muscle area (63.10 cm2) and sarcomere length (1.60 ?m), were not affected by SBW, but SBW increased cold carcass weight. The treatments had effects on the primary and commercial cut weights. However, the cut yields for the forequarter (39.84%), hindquarter (47.82%) and side-cut (12.34%), and the secondary cuts: chuck (14.38%), hump steak (1.94%), shoulder clod (16.97%), brisket point end (5.56%), neck steak (1.00%), striploin (7.77%), outside flat (5.30%), topside (9.36%), tenderloin (2.16%), flank steak (3.41%), eyeround (2.67%), rump tail (1.20%), rump eye (3.89%), shank (4.44%), knuckle (5.25%) and rump cap (1.40%), were not affected by SBW. SBW did not influence (p &gt; 0.05) the commercial cut compositions for all cuts in the forequarter and hindquarter. Finishing young bulls in a feedlot is a strategy to produce beef with reduced feed costs. After all, the slaughter body weight (350, 400 or 450 kg) influenced the quantitative characteristics of the carcass; however, it did not affect the yield of commercial cuts from young Nellore bulls.

Effects of electrical stimulation and pre-rigor conditioning temperature on aging potential of hot-boned beef M. longissimus lumborum.

The objective of this study was to create various pH/temp decline rates in hot-boned bull beef M.longissimus lumborum (LL) through a combination of electrical stimulation (ES) and pre-rigor holding temperature. The relationship between the pre-rigor interventions, the activities of µ-calpain and small heat shock proteins (sHSP), and the impacts on meat product quality were determined. Paired LL loins from 13 bulls were hot-boned within 40min of slaughter, immediately ES and subjected to various holding temperatures (5, 15, 25, and 35°C) for 3hr. The rate of muscle pH decline, sarcomere length, shear force, and proteolysis of muscle proteins were measured. ES-25°C had a longer sarcomere length compared to non-electrical stimulation samples. ES-25°C and ES-35°C samples had lower shear force values, higher µ-calpain activity and higher desmin, troponin-T, and sHSP degradation. The above findings suggest that pH/temp decline rates created in hot-boned muscle impacted muscle protein proteolysis by increasing the activity of proteases and degradation of sHSP.

Effect of visual marbling levels in pork loins on meat quality and Thai consumer acceptance and purchase intent.

ObjectiveWe investigated visual marbling level (VML) influence on pork loin physicochemical traits, consumer palatability responses, VML liking, purchase intent, and their relationships.MethodsFor each of five slaughtering dates, at 24-h postmortem, nine paired Duroc castrated male boneless Longissimus dorsi (LD) muscles were categorized into low (LM, score 1 to 2, n = 3), medium (MM, score 3 to 4, n = 3), and high (HM, score 5 to 6, n = 3) VML. Meat physicochemical quality traits and consumer responses (n = 389) on palatability and VML liking, and purchase intent were evaluated. The experiment was in randomized complete block design. Analysis of variance, Duncan’s multiple mean comparisons, and correlation coefficients were determined.ResultsVML correspond to crude fat (r = 0.91, p<0.01), but both were reversely related to moisture content (r = −0.75 and −0.91, p<0.01, respectively). As VML increased, ash (p<0.05) and protein (p = 0.072) decreased, pH and b* increased (p<0.05), but drip, cooking (p<0.05) and thawing (p = 0.088) losses decreased. Among treatments, muscle fiber diameter, sarcomere length, total and insoluble collagen contents, L*, and a* did not differ (p>0.05). Compared to the others, HM had lower collagen solubility percentage (p<0.05), but similar (p>0.05) Warner-Bratzler shear force (WBSF). No differences (p>0.05) were found in juiciness, overall flavor, oiliness, and overall acceptability, but HM was more tender (p<0.05) than the others. Based on VML, consumers preferred MM to HM (p<0.05), while LM was similar to MM and HM (p>0.05). Corresponding to VML preference (r = 0.45, p<0.01), consumers (83%) would (p<0.01) definitely and probably buy MM, over LM (74%), and HM (68%), respectively.ConclusionIncreasing VML in pork LD altered its chemical composition, slightly increased pH, and improved water holding capacity, thereby improving its tenderness acceptability. Marbling might reduce chewing resistance, as lower collagen solubility in HM did not impact tenderness acceptability and WBSF. While HM was rated as most tender, consumers visually preferred and would purchase MM.