Technical note: Protocol for electrophoretic separation of bovine myosin heavy chain isoforms and comparison to immunohistochemistry analysis

Expression profile and bioinformatics analysis of circRNA and its associated ceRNA networks in longissimus dorsi from Lufeng cattle and Leiqiong cattle

This paper aims to explore the role of circRNA expression profiles and circRNA-associated ceRNA networks in the regulation of myogenesis in the longissimus dorsi of cattle breeds surviving under subtropical conditions in southern China by RNA sequencing and bioinformatics analysis. It also aims to provide comprehensive understanding of the differences in muscle fibers in subtropical cattle breeds and to expand the knowledge of the molecular networks that regulate myogenesis. With regard to meat quality indicators, results showed that the longissimus dorsi of LQC had lower pH (P < 0.0001), lower redness (P < 0.01), lower shear force (P < 0.05), and higher brightness (P < 0.05) than the longissimus dorsi of LFC. With regard to muscle fiber characteristics, the longissimus dorsi of LQC had a smaller diameter (P < 0.0001) and higher density of muscle fibers (P < 0.05). The analysis results show that the function of many circRNA-targeted mRNAs was related to myogenesis and metabolic regulation. Furthermore, in the analysis of the function of circRNA source genes, we hypothesized that btacirc_00497 and btacirc_034497 may regulate the function and type of myofibrils by affecting the expression of MYH6, MYH7, and NEB through competitive linear splicing.

Semi-automated technique for bovine skeletal muscle fiber cross-sectional area and myosin heavy chain determination

Myosin heavy chain (MyHC) type and muscle fiber size are informative but time-consuming variables of interest for livestock growth, muscle biology, and meat science. The objective of this study was to validate a semi-automated protocol for determining MyHC type and size of muscle fibers. Muscle fibers obtained from the longissimus and semitendinosus of fed beef carcasses were embedded and frozen within 45 min of harvest. Immunohistochemistry was used to distinguish MyHC type I, IIA, and IIX proteins, dystrophin, and nuclei in transverse sections of frozen muscle samples. Stained muscle cross sections were imaged and analyzed using two workflows: 1) Nikon workflow which used Nikon Eclipse inverted microscope and NIS Elements software and 2) Cytation5 workflow consisting of Agilent BioTek Cytation5 imaging reader and Gen5 software. With the Cytation5 workflow, approximately six times more muscle fibers were evaluated compared to the Nikon workflow within both the longissimus (P < 0.01; 768 vs. 129 fibers evaluated) and semitendinosus (P < 0.01; 593 vs. 96 fibers evaluated). Combined imaging and analysis took approximately 1 h per sample with the Nikon workflow and 10 min with the Cytation5 workflow. When muscle fibers were evaluated by the objective thresholds of the Cytation5 workflow, a greater proportion of fibers were classified as glycolytic MyHC types, regardless of muscle (P < 0.01). Overall mean myofiber cross-sectional area was 14% smaller (P < 0.01; 3,248 vs. 3,780) when determined by Cytation5 workflow than when determined by Nikon workflow. Regardless, Pearson correlation of mean muscle fiber cross-sectional areas determined by Nikon and Cytation5 workflows was 0.73 (P < 0.01). In both workflows cross-sectional area of MyHC type I fibers was the smallest and area of MyHC type IIX fibers was the largest. These results validated the Cytation5 workflow as an efficient and biologically relevant tool to expedite data capture of muscle fiber characteristics while using objective thresholds for muscle fiber classification.

Body, carcass, and steak dimensions of straightbred Holstein calves and Angus-sired calves from Holstein, Jersey, and crossbred beef dams

Beef genetics are used with increasing frequency on commercial dairies. Although use of beef genetics improves calf value, variability has been reported in beef × dairy calf phenotype for traits related to muscularity and carcass composition. The objective of this study was to characterize morphometric and compositional differences between beef, beef × dairy, and dairy-fed cattle. Tested treatment groups included Angus-sired straightbred beef steers and heifers (A × B; n = 45), Angus × Holstein crossbreds (A × H; n = 15), Angus × Jersey crossbreds (A × J; n = 16), and straightbred Holsteins (H, n = 16). Cattle were started on trial at mean BW of 302 ± 29.9 kg and then fed at 196 ± 3.4 d. Morphometric measures were recorded every 28 d during the finishing period, ultrasound measures were recorded every 56 d, and morphometric carcass measures were recorded upon slaughter. Muscle biopsies were collected from the longissimus thoracis of a subset of steers (n = 43) every 56 d. Strip loins were collected from carcasses (n = 78) for further evaluation. Frame size measured as hip height, hip width, and body length was greatest for H cattle (P < 0.05), and A × H cattle had greater hip height than A × J cattle (P < 0.05). Relative to BW as a percentage of mature size, ribeye area of all cattle increased at a decreasing rate (negative quadratic term: P < 0.01), and all ultrasound measures of fat depots increased at an increasing rate (positive quadratic term: P < 0.01). Although no difference was observed in muscle fiber area across the finishing period from the longissimus thoracis (P = 0.80), H cattle had a more oxidative muscle phenotype than A × B cattle (P < 0.05). Additionally, H cattle had the smallest area of longissimus lumborum in the posterior strip loin, greatest length-to-width ratio of longissimus lumborum in the posterior strip loin, and least round circumference relative to round length (P < 0.05). Beef genetics improved muscularity in portions of the carcass distal to the longissimus thoracis.

Early Postmortem Metabolism and Protease Activation in Fast Glycolytic and Slow Oxidative Bovine Muscles

Muscle properties and metabolism influence muscle to meat conversion. Fiber type profile impacts glycolytic capacity as well as protein turnover rate in vivo. Our objective was to investigate protease content and activation during the early postmortem period using muscles with known divergent metabolism. Samples from longissimus lumborum (LL) and diaphragm (Dia) were taken from predominantly Angus steer carcasses (n = 6) at 1, 3, and 24 h postmortem and frozen. Myosin heavy chain (MyHC) isoforms, ATP, glycogen, glucose, glucose-6-phosphate (G6P), and lactate concentrations were determined. Procaspase-3, calpain-1, calpastatin, desmin, and troponin-T were assessed by immunodetection. Muscles showed contrasting MyHC profiles, with LL represented primarily by IIx and IIa isoforms (∼88%) whereas Dia contained mostly (80%) type I isoform. Glycogen degradation was more pronounced in LL and coincided with more rapid accumulation of glucose and lactate (P &lt; 0.01). Procaspase-3 content was influenced by muscle (m: P &lt; 0.01), being greater in Dia. Fragments indicating activation of procaspase-3 postmortem were not detected. Calpain-1 autolysis and intact calpastatin (135 kDa) content were influenced by muscle and time (m × t: P &lt; 0.01 and P &lt; 0.01, respectively). Calpastatin fragmentation postmortem was not associated with greater procaspase-3 content. In conclusion, fast glycolytic LL displayed faster protease activation and greater proteolysis during the first 24 h postmortem.

Mitochondrial Function in Oxidative and Glycolytic Bovine Skeletal Muscle Postmortem

Meat quality is traditionally associated with anaerobic metabolism due to cessation of the oxygen supply post-mortem. However, mitochondrial (mt) function early postmortem may affect the development of meat quality characteristics, such as adenosine triphosphate levels and pH decline. Therefore, the objective of this study was to evaluate mt function ex vivo during the first 24 h postmortem in muscles with differences in mt content. Samples from longissimus lumborum (LL) and diaphragm (Dia) were taken from steers (n = 6) at 1, 3, and 24 h postmortem and frozen to determine citrate synthase (CS) activity and mt protein expression (immunodetection) or were fresh-preserved for high-resolution respirometry. Integrative oxygen consumption rate (picomoles per second per milligram of tissue) was measured and normalized to CS activity as a proxy for mt content (intrinsic mt function, picomoles per second per unit CS). CS activity (P &lt; 0.001) and mt protein expression (P &lt; 0.001) were greater in Dia, which was reflected in mt respiration. Muscle type affected (P &lt; 0.001) integrative leak respiration and was greater in mt from Dia; oxidative phosphorylation (OXPHOS) was also greater in Dia and influenced by time postmortem (muscle × time: P = 0.01). Intrinsic leak and OXPHOS were affected by muscle and time (muscle × time: P = 0.05 and P = 0.01, respectively), with the most pronounced differences at 24 h postmortem. Stimulation of OXPHOS by cytochrome c as an indicator of outer mt membrane integrity was influenced by muscle and time postmortem (muscle × time: P = 0.03); it was greater in mt from LL. Despite intrinsic differences in respiratory function at 24 h, mt from both muscles were intact and coupled at 1 h postmortem. Reduced content and respiratory function in mt from LL are associated with early fragmentation, which could impact protease activation and subsequently meat quality.

Muscle Fiber Properties in Cattle and Their Relationships with Meat Qualities: An Overview

The control of meat quality traits constitutes an important target for any farm animal production, including cattle. Therefore, better understanding of the biochemical properties that drive muscle development and final outcomes constitutes one of the main challenging topics of animal production and meat science. Accordingly, this review has focused on skeletal muscle fibers in cattle and their relationships with beef qualities. It aimed to describe the chemical and structural properties of muscle fibers as well as a comprehensive review of their contractile and metabolic characteristics during the life of the animal. The existing methods for the classification of muscle fibers were reviewed, compared, and discussed. Then, the different stages of myogenesis in cattle were defined. The main factors regulating fetal and postnatal growth and the plasticity of muscle fibers were evidenced, especially the role of myostatin growth factor and the impact of nutritional factors. This review highlights that the knowledge about muscle fibers is paramount for a better understanding of how to control the muscle properties throughout the life of the animal for better management of the final eating qualities of beef. Accordingly, the associations between bovine muscle fibers and different meat eating qualities such as tenderness, pH decline, and color traits were further presented.

Myosin heavy chain isoforms expression, calpain system and quality characteristics of different muscles in goats

Myosin heavy chain (MHC) isoforms in goat muscles and their possible relationships with meat quality have not been fully elucidated. This study characterized the MHC isoforms in different caprine muscles using sodium dodecyl sulphate glycerol gel electrophoresis (SDS-GGE). The relationships between MHC isoforms, calpain systems and meat quality characteristics of different muscles in goats were examined. Four muscles, namely infraspinatus (IF), longissimus dorsi (LD), psoas major (PM) and supraspinatus (SS) were obtained from ten Boer crossbred bucks (7-10 months old; 26.5 ± 3.5 kg, BW). The percentages of MHC I, MHC IIa and MHC IIx in SS, IF, PM and LD were 47.2, 38.3, 32.1, 11.9; 28.0, 42.1, 33.0, 36.4; and 24.8, 19.6, 34.9 and 51.7, respectively. IF and SS had higher levels of calpastatin, total collagen and insoluble collagen contents than did PM and LD. PM had longer sarcomere length than did other muscles. LD had higher collagen solubility, troponin-T degradation products and glycogen content than did other muscles. These results infer that variable fiber-type composition could account partially for the differences in the physicochemical properties of goat muscles.