Changes in the muscle proteome after compensatory growth in pigs

Transcriptome analysis revealed differences in gene expression in sheep muscle tissue at different developmental stages

BACKGROUND

The analysis of differentially expressed genes in muscle tissues of sheep at different ages is helpful to analyze the gene expression trends during muscle development. In this study, the longissimus dorsi muscle of pure breeding Hu sheep (H), Suffolk sheep and Hu sheep hybrid F1 generation (SH) and East Friesian and Hu sheep hybrid sheep (EHH) three strains of sheep born 2 days (B2) and 8 months (M8) was used as the research object, and transcriptome sequencing technology was used to identify the differentially expressed genes of sheep longissimus dorsi muscle in these two stages. Subsequently, GO and KEGG enrichment analysis were performed on the differential genes. Nine differentially expressed genes were randomly selected and their expression levels were verified by qRT-PCR.

RESULTS

The results showed that 842, 1301 and 1137 differentially expressed genes were identified in H group, SH group and EHH group, respectively. Among them, 191 differential genes were enriched in these three strains, including pre-folding protein subunit 6 (PFDN6), DnaJ heat shock protein family member A4 (DNAJA4), myosin heavy chain 8 (MYH8) and so on. GO and KEGG enrichment analysis was performed on 191 differentially expressed genes shared by the three strains to determine common biological pathways. The results showed that the differentially expressed genes were significantly enriched in ribosomes, unfolded protein binding, FoxO signaling pathway, glycolysis / glycogen generation and glutathione signaling pathway that regulate muscle protein synthesis and energy metabolism. The results of qRT-PCR were consistent with transcriptome sequencing, which proved that the sequencing results were reliable.

CONCLUSIONS

Overall, this study revealed the important genes and signaling pathways related to sheep skeletal muscle development, and the result laid a foundation for further understanding the mechanism of sheep skeletal muscle development.

Effects of Different Na+ Concentrations on cAMP-Dependent Protein Kinase Activity in Postmortem Meat

cAMP-dependent protein kinase (PKA) activity regulates protein phosphorylation, with Na+ playing a crucial role in PKA activity. The aim of this study was to investigate the effects of different Na+ concentrations on PKA activity and protein phosphorylation level in postmortem muscle. The study consisted of two experiments: (1) NaCl of 0, 20, 100, 200 and 400 mM was added to a muscle homogenate incubation model to analyze the effect of Na+ concentration on PKA activity, and (2) the same concentrations were added to pure PKA in vitro incubation models at 4 °C to verify the effect of Na+ on PKA activity. The PKA activity of the muscle homogenate model increased with storage time in groups with different Na+ concentrations. High concentrations of Na+ inhibited sarcoplasmic protein phosphorylation. The PKA activity at 24 h of storage and the sarcoplasmic protein phosphorylation level at 12 h of storage in the group with 200 mM Na+ was lower than that of the other groups. After 1 h incubation, the PKA activity of samples in the 200 mM Na+ group was inhibited and lower than that in the other Na+ groups in the in vitro incubation model. These results suggest that the Na+ concentration at 200 mM could better inhibit PKA activity. This study provided valuable insights for enhancing curing efficiency and improving meat quality.

Carcass characteristics and meat quality of male pigs submitted to surgical or immunological castration

The objective of this study was to evaluate carcass characteristics and meat quality of surgically castrated and immunocastrated male pigs. Data were collected from 24 surgically castrated pigs and 24 immunocastrated male entire originating from the commercial line (Agroceres x Topigs), receiving isonutritive diets and were housed in the same experimental shed, slaughtered at 177 days old, with a slaughter weight of 127.8 (± 6.5) and 135.1 (± 7.8) kg, respectively. Carcass and meat quality characteristics such as carcass yield, lean meat yield, fat content, backfat thickness, muscle depth, pH, meat coloring and, drip, thawing and cooking loss, were evaluated. Immunocastrated pigs have heavier carcass, higher meat yield and lower fat thickness when compared to surgically castrated animals. Regarding meat quality, the immunocastrated presented a lighter meat, less reddness and less water holding capacity. In conclusion, this study confirmed that the carcass of male pigs, submitted immunocastration, has lower yield, however, more meat and less fat content, when compared to carcass of male pigs surgically castrated. Meat quality showed peculiar characteristics for immunocastrated pigs, and can be used more for sausage production, since it retains less water and have smaller redness color compared to surgically castrated pigs.

Involvement of glycolysis activation in flatfish sexual size dimorphism: Insights from transcriptomic analyses of Platichthys stellatus and Cynoglossus semilaevis

The starry flounder (Platichthys stellatus), a flatfish cultured at the margins of the North Pacific, displays an obvious female-biased growth advantage, similar to many other fish species. To reveal the molecular mechanism underlying sexual size dimorphism, a comparative transcriptomic analysis of the somatotropic and reproductive axes was conducted. In total, 156, 67, 3434, and 378 differentially expressed genes (DEGs) between female and male samples were obtained in the brain, liver, gonad, and muscle tissues (q < 0.05). These DEGs were significantly enriched for various GO terms, including ion channel activity, protein binding, lipid transporter activity, and glycolytic process. The significantly enriched KEGG pathways included insulin secretion, axon guidance, and glycolysis/gluconeogenesis. In a detailed analysis of DEGs in these significantly enriched pathways, 35 genes showed higher expression levels in female muscle tissues than in male muscle tissues. A protein-protein interaction network further revealed specific interactions involving the glycolysis related-protein enolase (ENO), triosephosphate isomerase (TPI), Bisphosphoglycerate mutase (BPGM), fructose-bisphosphate aldolase (ALDO), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, the role of glycolysis/gluconeogenesis was supported by an analysis of common DEGs between P. stellatus and Chinese tongue sole (Cynoglossus semilaevis). These results indicate that the activation of glycolysis in female muscle tissues contributes to flatfish sexual size dimorphism.

Whole Genome Sequence Data Provides Novel Insights Into the Genetic Architecture of Meat Quality Traits in Beef

Tenderness is a major quality attribute for fresh beef steaks in the United States, and meat quality traits in general are suitable candidates for genomic research. The objectives of the present analysis were to (1) perform genome-wide association (GWA) analysis for marbling, Warner-Bratzler shear force (WBSF), tenderness, and connective tissue using whole-genome data in an Angus population, (2) identify enriched pathways in each GWA analysis; (3) construct a protein-protein interaction network using the associated genes and (4) perform a μ-calpain proteolysis assessment for associated structural proteins. An Angus-sired population of 2,285 individuals was assessed. Animals were transported to a commercial packing plant and harvested at an average age of 457 ± 46 days. After 48 h postmortem, marbling was recorded by graders' visual appraisal. Two 2.54-cm steaks were sampled from each muscle for recording of WBSF, and tenderness, and connective tissue by a sensory panel. The relevance of additive effects on marbling, WBSF, tenderness, and connective tissue was evaluated on a genome-wide scale using a two-step mixed model-based approach in single-trait analysis. A tissue-restricted gene enrichment was performed for each GWA where all polymorphisms with an association p-value lower than 1 × 10-3 were included. The genes identified as associated were included in a protein-protein interaction network and a candidate structural protein assessment of proteolysis analyses. A total of 1,867, 3,181, 3,926, and 3,678 polymorphisms were significantly associated with marbling, WBSF, tenderness, and connective tissue, respectively. The associate region on BTA29 (36,432,655-44,313,046 bp) harbors 13 highly significant markers for meat quality traits. Enrichment for the GO term GO:0005634 (Nucleus), which includes transcription factors, was evident. The final protein-protein network included 431 interations between 349 genes. The 42 most important genes based on significance that encode structural proteins were included in a proteolysis analysis, and 81% of these proteins were potential μ-Calpain substrates. Overall, this comprehensive study unraveled genetic variants, genes and mechanisms of action responsible for the variation in meat quality traits. Our findings can provide opportunities for improving meat quality in beef cattle via marker-assisted selection.

Oversupplying metabolizable protein in late gestation for beef cattle: effects on postpartum ruminal fermentation, blood metabolites, skeletal muscle catabolism, colostrum composition, milk yield and composition, and calf growth performance

The objective of the study was to determine whether oversupplying MP prepartum affects postpartum cow BW, colostrum composition, milk production and composition, protein catabolism in the dam, and calf growth. Crossbred Hereford heifers were individually fed a control treatment designed to meet MP requirements (CON; n = 10) or 133% of the MP requirement (HMP; n = 11) from day -55 ± 4 until parturition. All cows were provided a common postpartum diet. Cow BW was measured on days 7 ± 1, 14 ± 2, 28 ± 3, 57 ± 4, 82 ± 5, and 111 ± 3 relative to parturition. DMI and ruminal pH were measured daily and summarized by week until day 33. Milk yield was estimated based on a 12-h two-quarter milk yield on days 7 ± 1, 12 ± 1, 28 ± 3, 33 ± 3, 70 ± 3, and 112 ± 3. Urine samples were collected from cows over a 6-d period starting on days 7 ± 1 and 28 ± 3 and the composited samples were analyzed for 3-methylhistidine (3-MH) and creatinine. Muscle samples were collected from cows on day 13 ± 1 while calf muscle samples were collected on days 2 and 111 ± 3 of age. Muscle samples from cows were analyzed for markers of protein catabolism, and calf muscle samples were analyzed for genes regulating cell growth and differentiation. Data were analyzed as a randomized complete block design using the MIXED procedure of SAS accounting for repeated measures when necessary. Postpartum BW did not differ (P ≥ 0.30) by treatment, day, or the interaction of treatment and day (T × D), but rump fat decreased (P = 0.011) as lactation progressed. DMI decreased during weeks 2 and 3 compared to 1 and 4, whereas ruminal pH was less during weeks 2, 3, and 4 relative to week 1. Colostrum fat concentration was less (P = 0.003) for HMP than CON; but, milk production was not affected by treatment. Milk yield was greatest from days 7 to 33 and decreased thereafter (P < 0.01). Urinary 3-MH and the 3-MH:creatinine ratio did not differ by treatment, day, or the T × D (P ≥ 0.22) interaction, nor was there a difference (P ≥ 0.13) in the abundance of catabolic proteins. Calf growth was not affected by treatment, but HMP calves had greater expression (T × D, P = 0.05) of PPARG while PKM expression increased for CON calves (T × D, P = 0.04) at day 111 compared to their expression at day 2. Overfeeding MP during late gestation does not improve postpartum indicators of N balance or maternal muscle turnover but may alter colostrum composition and calf gene expression at weaning.

Meat quality traits and proteome profile of woody broiler breast (pectoralis major) meat

Woody breast meat has recently become prevalent in the broiler industry in both the United States and European Union. Recent publications have described the meat quality characteristics of woody breast meat as having hardened areas and pale ridge-like bulges at both the caudal and cranial regions of the breast. The present study investigated the meat quality (pH, color, cooking loss, and shear force) and protein quality characteristics (protein and salt-soluble protein content) in woody breast meat as compared to normal breast meat. In addition, the differences in the muscle proteome profiles of woody and normal breast meat were characterized. Results indicated that woody breast meat had a greater average pH (P < 0.0001) and cooking loss (P = 0.001) than normal breast meat, but woody breast meat did not differ in shear force (P > 0.05) in comparison to normal breast meat samples. The L*, a*, and b* values of woody breast fillets were greater than normal breast fillets (P < 0.0001 to L*; P = 0.002 to a*; P = 0.016 to b*). The woody breast meat had more fat (P < 0.0001) and moisture (P < 0.021) and less protein (P < 0.0001) and salt-soluble protein (P < 0.0001) when compared with normal breast fillets. Whole muscle proteome analysis indicated 8 proteins that were differentially expressed (P < 0.05) between normal and woody breast meat samples. The differences in muscle proteome between normal and woody breast meat indicated an increased oxidative stress in woody breast meat when compared to normal meat. In addition, the abundance of some glycolytic enzymes, which are critical to the regeneration of adenosine triphosphate (ATP) in postmortem muscles, was lower in woody breast meat than in normal breast meat. Proteomic differences provide additional information on the biochemical pathways and genetic variations that lead to woody breast meat. Further research should be conducted to elucidate the genetic and nutritional contributions to the proliferation of woody breast meat in the United States.

Proteomic approach to characterize biochemistry of meat quality defects

Proteomics can be used to characterize quality defects including pale, soft, and exudative (PSE) meat (pork and poultry), woody broiler breast meat, reddish catfish fillets, meat toughness, and beef myoglobin oxidation. PSE broiler meat was characterized by 15 proteins that differed in abundance in comparison to normal broiler breast meat, and eight proteins were differentially expressed in woody breast meat in comparison to normal breast meat. Hemoglobin was the only protein that was differentially expressed between red and normal catfish fillets. However, inducing low oxygen and/or heat stress conditions to catfish fillets did not lead to the production of red fillets. Proteomic data provided information pertaining to the protein differences that exist in meat quality defects. However, these data need to be evaluated in conjunction with information pertaining to genetics, nutrition, environment of the live animal, muscle to meat conversion, meat quality analyses and sensory attributes to understand causality, protein biomarkers, and ultimately how to prevent quality defects.

Phosphoproteomic profiling of myofibrillar and sarcoplasmic proteins of muscle in response to salting

A phosphoproteomic profile of myofibrillar and sarcoplasmic proteins of muscle in response to salting was investigated. Myofibrillar and sarcoplasmic proteins extracted from salted meat with 0, 1, 2, 3, 4, and 5% salt for 0, 2, 4, 6, 8, and 16 h were analyzed by SDS-PAGE electrophoresis and fluorescence staining. The global phosphorylation of myofibrillar proteins in salted meat was lower than that in control muscle at 16 h of salting (p<0.05), and the global phosphorylation of myofibrillar proteins in 3% salt-treated group at 16 h was the lowest. However, salting showed no significant effect on phosphorylation of sarcoplasmic proteins. Four categories of phosphorylated protein were identified by LC-MS/MS, involved in stress response (heat shock protein), glycometabolism (glycogen phosphorylase, glyceraldehyde-3-phosphate dehydrogenase), oxidation or reduction (superoxide dismutase), and others (myoglobin), the phosphorylation of which was affected by salting. Thus, salting may influence meat quality through protein phosphorylation, which regulates protein degradation and glycolysis.

TRIENNIAL LACTATION SYMPOSIUM: Nutrigenomics in livestock: Systems biology meets nutrition

The advent of high-throughput technologies to study an animal's genome, proteome, and metabolome (i.e., "omics" tools) constituted a setback to the use of reductionism in livestock research. More recent development of "next-generation sequencing" tools was instrumental in allowing in-depth studies of the microbiome in the rumen and other sections of the gastrointestinal tract. Omics, along with bioinformatics, constitutes the foundation of modern systems biology, a field of study widely used in model organisms (e.g., rodents, yeast, humans) to enhance understanding of the complex biological interactions occurring within cells and tissues at the gene, protein, and metabolite level. Application of systems biology concepts is ideal for the study of interactions between nutrition and physiological state with tissue and cell metabolism and function during key life stages of livestock species, including the transition from pregnancy to lactation, in utero development, or postnatal growth. Modern bioinformatic tools capable of discerning functional outcomes and biologically meaningful networks complement the ever-increasing ability to generate large molecular, microbial, and metabolite data sets. Simultaneous visualization of the complex intertissue adaptations to physiological state and nutrition can now be discerned. Studies to understand the linkages between the microbiome and the absorptive epithelium using the integrative approach are emerging. We present examples of new knowledge generated through the application of functional analyses of transcriptomic, proteomic, and metabolomic data sets encompassing nutritional management of dairy cows, pigs, and poultry. Published work to date underscores that the integrative approach across and within tissues may prove useful for fine-tuning nutritional management of livestock. An important goal during this process is to uncover key molecular players involved in the organismal adaptations to nutrition.

Phosphorylation of myofibrillar proteins in post-mortem ovine muscle with different tenderness

BACKGROUND

Tenderness is one of the most important quality attributes especially for beef and lamb. As protein phosphorylation and dephosphorylation regulate glycolysis, muscle contraction and turnover of proteins within living cells, it may contribute to the conversion of muscle to meat. The changes of myofibrillar protein phosphorylation in post-mortem ovine muscle with different levels of tenderness were investigated in this study.

RESULTS

The protein phosphorylation level (P/T ratio) of the tender group increased from 0.5 to 12 h post mortem and then decreased. The P/T ratio of tough group increased during 24 h post mortem, increasing faster from 0.5 to 4 h post mortem than from 4 to 24 h post mortem.The global phosphorylation level of tough meat was significantly higher than tender meat at 4, 12 and 24 h post mortem (P < 0.05). Protein identification revealed that most of the phosphoproteins were proteins with sarcomeric function; the others were involved in glycometabolism, stress response, etc. The phosphorylation levels of myofibrillar proteins, e.g. myosin light chain 2 and actin, were significantly different among groups of different tenderness and at different post-mortem time points (P < 0.05).

CONCLUSION

Protein phosphorylation may influence meat rigor mortis through contractile machinery and glycolysis, which in turn affect meat tenderness.

Proteomics in food: Quality, safety, microbes, and allergens

Food safety and quality and their associated risks pose a major concern worldwide regarding not only the relative economical losses but also the potential danger to consumer's health. Customer's confidence in the integrity of the food supply could be hampered by inappropriate food safety measures. A lack of measures and reliable assays to evaluate and maintain a good control of food characteristics may affect the food industry economy and shatter consumer confidence. It is imperative to create and to establish fast and reliable analytical methods that allow a good and rapid analysis of food products during the whole food chain. Proteomics can represent a powerful tool to address this issue, due to its proven excellent quantitative and qualitative drawbacks in protein analysis. This review illustrates the applications of proteomics in the past few years in food science focusing on food of animal origin with some brief hints on other types. Aim of this review is to highlight the importance of this science as a valuable tool to assess food quality and safety. Emphasis is also posed in food processing, allergies, and possible contaminants like bacteria, fungi, and other pathogens.

Effect of vaccination against gonadotropin-releasing hormone (GnRH) in heavy male pigs for Italian typical dry-cured ham production

The aim of this study was to evaluate immunocastration (vaccination against GnRH using Improvac® vaccine), as an alternative to surgical castration in heavy male pigs (average live weight 165 ± 10 kg), used in the production of Italian typical dry-cured ham. A total of 60 Landrace × Large White male pigs were assigned to three groups of 20 units, including one group of surgically castrated (SC), and two of immunocastrated pigs, with two (IC2) or three (IC3) vaccine treatments, respectively. The groups were compared for green ham traits, processing weight losses, chemo-physical, and sensory properties of dry-cured hams. While IC3 were not different (P>0.05) from SC group, IC2 hams were found to differ (P<0.05) both from SC and IC3 groups in ham traits, final weight losses, texture and sensory boar taint in finished hams. Therefore, vaccination with three doses could be taken into account to control boar taint in the manufacturing of typical Italian dry-cured ham.

Dietary L-arginine supplementation affects the skeletal longissimus muscle proteome in finishing pigs

Forty-eight Duroc x Landrace x Large White gilts were used to determine the relationship between proteome changes of longissimus muscle and intramuscular fat (IMF) content in arginine-supplemented pigs. Beginning at 60 kg BW, pigs were fed a corn- and soybean meal-based diet supplemented or not with 1% L-arginine until they reached a BW of 100 kg. Supplementation with 1% L-arginine did not affect the growth performance or carcass traits, while it increased IMF content by 32% (P < 0.01), it also decreased the drip loss at 48 h post-mortem and the b* meat color value at 24 h post-mortem; supplementation with 1% dietary L-arginine did not change the proportion of SFA and MUFA in muscle lipids. The proteome changes in longissimus muscle between the control and supplemented pigs showed that L-arginine significantly influenced the abundance of proteins related to energy metabolism, fiber type and structure. The increase in IMF content was positively correlated with the increased abundance of slow twitch troponin I (TNNI1) protein and negatively correlated with myosin heavy chain IIb (MyHC IIb) protein content. It is suggested that the proteome changes in longissimus muscle contributed to the greater IMF content in L-arginine supplemented pigs.

Effect of cooking on in vitro digestion of pork proteins: a peptidomic perspective

This study was designed to investigate the effect of cooking on in vitro digestibility and peptide profiling of pork protein. We simulated gastrointestinal digestion of cooked pork that was treated with pepsin alone or followed by trypsin treatment. Digested products were identified using matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry and liquid chromatography–mass spectrometry analyses. Cooking led to a reduction (p < 0.05) in digestibility and band intensities on sodium dodecyl sulfate–polyacrylamide gel electrophoresis gels. Peptide profiling and identification analyses also showed significant difference (p < 0.05) in the m/z ranges and number of peptides from the pepsin-digested products between raw (4 °C) and very well done samples (100 °C). Peptides sequenced from pepsin-digested samples under lower degrees of doneness disappeared as the temperature increased. Meanwhile, the trypsin cleavages appeared more consistent among different degrees of cooking. Further work may be needed to evaluate the bioavailability of the digested products under different cooking temperatures.

Impact of nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs

An experiment was conducted to examine the effect of the nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs. Four dietary treatments were used in a 2 × 2 factorial arrangement of treatments based on diet complexity (Complex vs. Simple) and in-feed antibiotics (2,730 [+AB] vs. 0 [-AB] mg of chlortetracycline /kg].A total of 552 pigs, in 5 blocks, were weaned at 21 ± 2 d of age with an initial BW of 7.03 ± 0.07 kg. Each experimental block had 3 pens per treatment, with 8 pigs per pen in blocks 1 and 2, and 10 pigs per pen in the remaining 3 blocks. Nursery diets were fed in a 3-phase feeding program (Phase I, II, and III diets fed for 1, 2, and 3 wk, respectively). All pigs were fed common grower-finisher diets thereafter. Six pigs per treatment were slaughtered for chemical body composition analysis at wk 2, 8, 12, and 17 postweaning. An additional 11 pigs per treatment were slaughtered at wk 17 postweaning (approximately 115 kg BW or market weight) for analysis of carcass characteristics, chemical and physical body composition, and meat quality. During the nursery phase, ADG was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (491 vs. 528 g/d). Antibiotic usage improved (P < 0.05) ADG in Phases II (408 vs. 438 g/d) and III (689 vs. 720 g/d). In Phase I and II, G:F was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (0.46 vs. 0.58 and 0.75 vs. 0.78 in Phases I and II, respectively). During the grower phase, pigs previously fed -AB diets grew faster than pigs fed +AB diets (P < 0.05; 1,009 vs. 971 g/d). There were no treatment effects on overall ADG or G:F from weaning to finishing. Nursery feeding program did not affect carcass quality characteristics. However, pigs previously fed +AB diets tended (P = 0.07) to have increased LM depth. Nursery feeding program had no effect on objective or subjective meat quality measures, chemical body composition, or the weight of primal and retail carcass cuts at wk 17 postweaning, with the exception of primal belly weight. These results indicate that feeding simple nursery diets, or nursery diets without antibiotics, compromises growth performance during the nursery period but does not affect overall growth performance between weaning and market BW, carcass characteristics, and meat quality. Thus, feed costs for nursery pigs can be reduced by feeding simple diets without compromising market BW and carcass and meat quality.

Molecular heterogeneities of adipose depots - potential effects on adipose-muscle cross-talk in humans, mice and farm animals

Adipose tissue is considered as a major endocrine organ that secretes numerous proteins called adipokines. The heterogeneous nature of adipose tissue in different parts of the body suggests respective heterogeneity of proteomes and secretomes. This review consolidates knowledge from recent studies targeting the diversity of different adipose depots affecting the pattern of secreted adipokines and discusses potential consequences for the cross-talk between adipose and skeletal muscle in humans, rodent models and farm animals. Special attention is paid to muscle-associated fat depots like inter- and intramuscular fat that become focus of attention in the context of the rather new notion of skeletal muscle as a major endocrine organ. Understanding the complexity of communication between adipocytes and skeletal muscle cells will allow developing strategies for improvement of human health and for sustainable production of high quality meat.

Proteomic profiling of bovine M. longissimus lumborum from Crossbred Aberdeen Angus and Belgian Blue sired steers varying in genetic merit for carcass weight

Bovine skeletal muscle is a tissue of significant value to the beef industry and global economy. Proteomic analyses offer the opportunity to detect molecular mechanisms regulating muscle growth and intramuscular fat accumulation. The current study aimed to investigate differences in protein abundance in skeletal muscle tissue of cattle from two breeds of contrasting maturity (early vs. late maturing), adiposity, and muscle growth potential, namely, Belgian Blue (BB) × Holstein Friesian and Aberdeen Angus (AA) × Holstein Friesian. Twenty AA (n = 10) and BB (n = 10) sired steers, the progeny of sires of either high or low genetic merit, expressed as expected progeny difference for carcass weight (EPDcwt), and bred through AI, were evaluated as 4 genetic groups, BB-High, BB-Low, AA-High, and AA-Low (n = 5 per treatment). Chemical composition analysis of M. longissimus lumborum showed greater protein and moisture and decreased lipid concentrations for BB-sired compared with AA-sired steers. To investigate the effects of both sire breed and EPDcwt on M. longissimus lumborum, proteomic analysis was performed using 2-dimensional difference gel electrophoresis followed by mass spectrometry. Proteins were identified from their peptide sequences, using the National Center for Biotechnology Information (NCBI) and Swiss-prot databases. Metabolic enzymes involved in glycolysis (glycogen phosphorylase, phosphoglycerate mutase) and the citric acid cycle (aconitase 2, oxoglutarate dehydrogenase) were increased in AA- vs. BB-sired steers. Expression of proteins involved in cell structure, such as myosin light chain isoforms and troponins I and T, were also altered due to sire breed. Furthermore, heat shock protein β-1 and peroxiredoxin 6, involved in cell defense, had increased abundance in muscle of AA-sired relative to BB-sired steers. Protein abundance of glucose-6-phosphate isomerase, enolase-3, and pyruvate kinase was greater in AA-sired animals of High compared with Low EPDcwt. Changes in the expression of these proteins were supported by gene expression analysis using quantitative real-time PCR. This information will aid in our understanding of genetic influences controlling muscle growth and fat accumulation and could contribute to future breeding programs to increase lean tissue gain of beef cattle.

Meta-analysis of the effect of immunocastration on production performance, reproductive organs and boar taint compounds in pigs

Meta-analytical approach was used to quantitatively synthesize the effect of immunocastration on growth, carcass, meat quality, reproductive organs and boar taint compounds. Altogether, 41 papers were collected for effect size (θ) calculation and the comparisons were made with entire males (EM) and surgical castrates (SC). The data for reproductive organs and growth performance are numerous enough to draw firm conclusions. In contrast, data for carcass and meat quality are more limited. Results of meta-analysis show efficient immunocastration with the magnitude of the response being by far the largest for reproductive organs (θ = -2.8 to -5.0) and boar taint substances (θ = -2.8 and -0.8 for androstenone and skatole, respectively). However, compared with SC, the immunocastrates exhibit larger bulbourethral glands (θ = 1.3) and slightly higher concentrations of androstenone and skatole (θ = 0.1 and θ = 0.2, respectively). The impact of immunocastration is also remarkable on performance, where the main advantage of the immunocastrates is their boar-like performance until revaccination. In the period following the second vaccination, they eat much more than EM (θ = 2.1), resulting in large effect size for growth rate compared with both EM and SC (θ = 1.1 and θ = 1.4, respectively). Considering the whole fattening period, their feed conversion ratio is higher compared with EM (θ = 0.6) and much lower than that of SC (θ = -1.3), although exhibiting moderately faster growth compared with both (θ = 0.6 and θ = 0.2, respectively). With regard to carcass quality, the immunocastrates take intermediate position between EM and SC. Besides, our analysis suggests no difference in meat quality with SC and some meat quality advantages of immunocastrates over EM because of higher intramuscular fat content (θ = 0.4) and lower shear force (θ = -0.6).

Proteomic analysis and differential expression in protein extracted from chicken with a varying growth rate and water-holding capacity

Chickens from a randomly bred genetic line were segregated into high and low growth rates and high and low water-holding capacities (WHCs). The objective of this study was to identify protein markers associated with slow and fast growth rates and low and high WHCs from water-soluble protein (WSP) and crude myofibrillar protein (CMP) extracts of chicken breast muscle. Proteins were fractionated using two-dimensional electrophoresis, and a total of 22 protein spots were selected, excised, and analyzed by in-gel tryptic digestion and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Proteins expressed in extracts from slow and fast growth rates and low and high WHCs included metabolic enzymes, such as creatine kinase, pyruvate kinase, triosephosphate isomerase, and ubiqitin; housekeeping proteins, such as heat shock protein; contractile proteins, such as myosin heavy chain; actin; and also MHC isoforms and actin isoforms. The mass spectra of 20 protein spots significantly matched (protein score >83; P < 0.05) an online database. In CMP, there were unique proteins that were present only in the fast-growth population: gi|118099530 , gi|20664362 , gi|71895043 , gi|114794125 , gi|297343122 , and gi|71895043 . This information identified protein markers associated with growth rate and water holding capacity. Some of those protein markers could be added to the chicken database.

Electrical stimulation affects metabolic enzyme phosphorylation, protease activation, and meat tenderization in beef

The objective of this study was to investigate the response of sarcoplasmic proteins in bovine LM to low-voltage electrical stimulation (ES; 80 V, 35 s) after dressing and its contribution to meat tenderization at an early postmortem time. Proteome analysis showed that ES resulted in decreased (P < 0.05) phosphorylation of creatine kinase M chain, fructose bisphosphate aldolase C-A, β-enolase, and pyruvate kinase at 3 h postmortem. Zymography indicated an earlier (P < 0.05) activation of μ-calpain in ES muscles. Free lysosomal cathepsin B and L activity increased faster (P < 0.05) in ES muscles up to 24 h. Immunohistochemistry and transmission electron microscopy further indicated that lysosomal enzymes were released at an early postmortem time. Electrical stimulation also induced ultrastructural disruption of sarcomeres. In addition, ES accelerated (P < 0.05) the depletion of ATP, creatine phosphate, and glycogen, as well as a pH decline and the more preferred pH/temperature decline mode. Finally, ES accelerated meat tenderization, resulting in lesser (P < 0.05) shear force values than the control over the testing time. A possible relationship was suggested between a change in the phosphorylation of energy metabolic enzymes and the postmortem tenderization of beef. Our results suggested the possible importance of the activation of μ-calpain, phosphorylation of sarcoplasmic proteins, and release of lysosomal enzymes for ES-induced tenderization of beef muscle.

Postmortem changes in pork muscle protein phosphorylation in relation to the RN genotype

Postmortem changes in pork muscle protein phosphorylation in relation to the RN(-) genotype were investigated using one-dimensional gel electrophoresis and a phosphor specific staining. The phosphorylation levels of several protein bands were found to be affected by the RN(-) genotype and to change during postmortem development. Glycogen phosphorylase, phosphofructokinase, and pyruvate kinase were found in protein bands affected by the RN(-) genotype, and the phosphorylation profile indicates that part of the increased rate and extended pH decline of the RN(-) genotype could be a consequence of phosphorylation of these key enzymes during the postmortem metabolism. The results illustrate that the protein phosphorylation level of the muscle proteins could be interpreted as a global metabolic fingerprint containing information about the activity status of the enzymes in the postmortem metabolism.

Differences in two-dimensional gel electrophoresis patterns of skeletal muscle myosin light chain isoforms between Bos taurus, Sus scrofa and selected poultry species

BACKGROUND

In this study the interspecies differences in two-dimensional electrophoresis patterns of skeletal muscle myosin light chain (MLC) isoforms between Bos taurus (cattle), Sus scrofa (pig), Gallus gallus (chicken), Meleagris gallopavo (turkey), Anas platyrhynchos (duck) and Anser anser (goose) were characterised on the basis of specific properties of MLCs associated with their structure and mobility in gel.

RESULTS

Two-dimensional electrophoresis separations revealed species-specific differences in the molecular weight and pI of individual MLC isoforms (MLC1f, MLC2f and MLC3f). In the case of closely related animal species such as goose and duck or turkey and chicken, significant differences occurred in MLC1f. For MLC2f, differences between cattle and turkey and between pig and chicken were around 1 and 0.3 kDa respectively. It appeared from the comparison of amino acid sequences that even MLCs with only 2% difference in sequences have different electrophoretic mobilities.

CONCLUSION

Interspecies differences in skeletal MLC isoforms appeared between cattle, pig, chicken, turkey, duck and goose. The slight changes observed in the course of the aging process confirmed that these proteins are relatively little susceptible to proteolytic enzymes during meat aging.

Skeletal muscle proteomics: current approaches, technical challenges and emerging techniques

Background

Skeletal muscle fibres represent one of the most abundant cell types in mammals. Their highly specialised contractile and metabolic functions depend on a large number of membrane-associated proteins with very high molecular masses, proteins with extensive posttranslational modifications and components that exist in highly complex supramolecular structures. This makes it extremely difficult to perform conventional biochemical studies of potential changes in protein clusters during physiological adaptations or pathological processes.

Results

Skeletal muscle proteomics attempts to establish the global identification and biochemical characterisation of all members of the muscle-associated protein complement. A considerable number of proteomic studies have employed large-scale separation techniques, such as high-resolution two-dimensional gel electrophoresis or liquid chromatography, and combined them with mass spectrometry as the method of choice for high-throughput protein identification. Muscle proteomics has been applied to the comprehensive biochemical profiling of developing, maturing and aging muscle, as well as the analysis of contractile tissues undergoing physiological adaptations seen in disuse atrophy, physical exercise and chronic muscle transformation. Biomedical investigations into proteome-wide alterations in skeletal muscle tissues were also used to establish novel biomarker signatures of neuromuscular disorders. Importantly, mass spectrometric studies have confirmed the enormous complexity of posttranslational modifications in skeletal muscle proteins.

Conclusions

This review critically examines the scientific impact of modern muscle proteomics and discusses its successful application for a better understanding of muscle biology, but also outlines its technical limitations and emerging techniques to establish new biomarker candidates.

Relationship between proteome changes of Longissimus muscle and intramuscular fat content in finishing pigs fed conjugated linoleic acid

The present experiment was conducted to determine proteome changes in Longissimus muscle of finishing pigs fed conjugated linoleic acid (CLA), in association with alteration of intramuscular fat content. Previously, seventy-two Duroc × Landrace × Large White gilts (approximately 60 kg) had been fed maize–soyabean meal-based diets with 0, 12·5 and 25 g CLA/kg diet. The CLA contained 369·1 mg/g cis-9, trans-11 CLA, 374·6 mg/g trans-10, cis-12 CLA and 53·7 mg/g other isomers. Six pigs per treatment were slaughtered when they reached a body weight of approximately 100 kg. Data published from a previous experiment demonstrated that supplementation with 12·5 or 25 g CLA/kg diet increased intramuscular fat content (P < 0·05). The present study investigated the proteome changes in Longissimus muscle of control and pigs supplemented with 25 g CLA/kg diet. CLA significantly influenced the abundance of proteins related to energy metabolism, fatty acid oxidation and synthesis, amino acid metabolism, defence, transport and other miscellaneous processes (P < 0·05). The increase in intramuscular fat content was positively correlated with the increased abundance of carbonic anhydrase 3 and aspartate aminotransferase (P < 0·05). We suggest that the proteome changes in Longissimus muscle contributed to greater intramuscular lipid content in CLA-supplemented pigs.

Proteomics of skeletal muscle differentiation, neuromuscular disorders and fiber aging

Skeletal muscle fibers are the most abundant cellular structure in the human body. Altered neuromuscular activity, traumatic injury or genetic abnormalities have profound effects on muscle integrity, tissue mass, fiber type distribution, metabolic integration and contractile function. The recent application of mass spectrometry-based proteomics has decisively advanced our molecular understanding of numerous physiological adaptations in healthy muscle and pathophysiological mechanisms associated with major muscle diseases. Skeletal muscle proteomics promises to play a major role in the establishment of a disease-specific biomarker signature for the major classes of neuromuscular disorders. New muscle markers will be crucial for the development of improved diagnostics, the monitoring of disease progression, evaluation of drug action and the identification of novel therapeutic targets.

Skeletal muscle proteomics in livestock production

Proteomics allows studying large numbers of proteins, including their post-translational modifications. Proteomics has been, and still are, used in numerous studies on skeletal muscle. In this article, we focus on its use in the study of livestock muscle development and meat quality. Changes in protein profiles during myogenesis are described in cattle, pigs and fowl using comparative analyses across different ontogenetic stages. This approach allows a better understanding of the key stages of myogenesis and helps identifying processes that are similar or divergent between species. Genetic variability of muscle properties analysed by the study of hypertrophied cattle and sheep are discussed. Biological markers of meat quality, particularly tenderness in cattle, pigs and fowl are presented, including protein modifications during meat ageing in cattle, protein markers of PSE meat in turkeys and of post-mortem muscle metabolism in pigs. Finally, we discuss the interest of proteomics as a tool to understand better biochemical mechanisms underlying the effects of stress during the pre-slaughter period on meat quality traits. In conclusion, the study of proteomics in skeletal muscles allows generating large amounts of scientific knowledge that helps to improve our understanding of myogenesis and muscle growth and to control better meat quality.

Comparative proteomic profiling of 2 muscles from 5 different pure pig breeds using surface-enhanced laser desorption/ionization time-of-flight proteomics technology

The objectives of this study were to evaluate the influence of different pure pig breeds and muscle types on the expression of muscle proteins, as well as their interactions, and second, to find biomarkers for breed and muscle types. A total of 126 male pigs, including 43 Landrace, 21 Duroc, 43 Large White, 13 Pietrain, and 6 Belgian Landrace, were slaughtered at the age of 174 +/- 6 d. Samples from the semimembranosus muscle (SM) and LM were collected 24 h postmortem. Proteomic spectra were generated on an anion exchanger (Q10), a cation exchanger (CM10), and on immobilized metal affinity capture (IMAC30) ProteinChip arrays and analyzed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry ProteinChip techniques. Breed and muscle type did not affect the number of peaks per spectrum but, interestingly, affected the average intensity of the peaks. Of these peaks, a total of 4 proved to be potential protein biomarkers to differentiate LM or SM muscles, and 2 to classify specific breed types. Additionally, several peaks influenced by the interaction between muscle and breed types could correctly classify pig muscles according to their breed. Further studies need to be carried out to validate and identify these potential protein biomarkers for breed and muscle types in finishing pigs.

Effect of the degree and duration of early dietary amino acid restrictions on subsequent and overall pig performance and physical and sensory characteristics of pork

The objective of this study was to investigate the effect of the degree and duration of early dietary AA restrictions on subsequent and overall pig performance and physical and sensory characteristics of pork. For the grower (G) and finisher-1 (F1) phases, 3 corn-soybean meal diets were formulated to contain 100, 80, or 60% of the 1998 NRC total Lys recommendations (100G, 80G, or 60G, and 100F1, 80F1, or 60F1, for the G and F1 phases, respectively). For the finisher-2 (F2) phase, a common corn-soybean meal diet was formulated to satisfy the 1998 NRC total Lys recommendation. Thirty gilts and 30 castrated males (2 gilts or 2 castrated males/pen) were randomly assigned to 5 dietary treatments (100G-100F1, 80G-100F1, 80G-80F1, 60G-100F1, and 60G-60F1) when BW was 22.7 +/- 0.3 kg. Pigs were switched to F1 and F2 diets at 50.7 +/- 0.4 and 79.9 +/- 0.5 kg of BW, respectively. Pigs had ad libitum access to feed and water. All pigs were slaughtered at 110.7 +/- 0.5 kg of BW, and LM samples were collected. Pigs fed the 60G diet had less (P < or = 0.05) ADG during the G phase and greater (P < or = 0.05) ultrasound backfat (UBF) at the end of the G phase than those fed the 100G diet. The ADG decreased linearly (R(2) = 0.70; P < 0.001) as the degree of AA restrictions became more severe. Although serum total protein (TP) and albumin concentrations in pigs fed the 60G-100F1 diets were less (P < or = 0.05) than those fed the 100G-100F1 diets at the end of the G phase, TP concentration was similar between the 2 groups at the end of the F1 phase. Likewise, ADG during the F1 phase and UBF at the end of the F1 phase in pigs fed the 60G-100F1 diets were similar to those fed the 100G-100F1 diets. Feeding the 80G diet resulted in numerically decreased ADG during the G phase, but there was no difference in ADG during the F1 and F2 phases or UBF at the end of F1 and F2 phases between pigs fed the 80G and 100G diets. Overall, pigs fed the 80G-80F1 diets had similar ADG, but less (P < or = 0.05) fat-free lean gain (LG) than those fed the 100G-100F1 diets. These pigs also had less (P < or = 0.05) serum TP and albumin concentrations than pigs fed the 100G-100F1 diets throughout the study. Pigs fed the 60G-60F1 diets had less (P < or = 0.05) overall ADG and G:F and less (P < or = 0.05) LM area and LG than those fed the 100G-100F1 diets. However, they had a greater (P < or = 0.05) subjective marbling score than those fed the 100G-100F1 diets. The results indicated that pigs fed the 80G-80F1 diets may have exhibited compensatory growth in BW gain, but not in terms of lean accretion. Growth performance and carcass traits of pigs fed the 60G-60F1 diets were reduced, indicating that the restriction may have been too severe or too long or both. Early dietary AA restrictions had no clear effect on physical and sensory characteristics of pork.