The effect of interaction between genotype CAST/RsaI (calpastatin) and MYOG/MspI (myogenin) on carcass and meat quality in pigs free of RYR1(T) allele

The purpose of the studies was to demonstrate to what degree genotypes of calpastatin (CAST/RsaI) and myogenin (MYOG) genes as well as the interaction between them may affect the carcass and meat quality of pigs. The investigations were conducted on 397 stress resistant pigs (free of RYR1^T allele). It was demonstrated that the favourable effect of the variants of CAST and MYOG genes on carcass quality traits depends on the cut. The gene variant favourably affecting the weight of ham simultaneously had a negative effect on the weight of the loin. It was also shown that the interaction between CAST and MYOG genotypes has a significant effect on backfat thickness. The effect of a given combination of CAST and MYOG genotypes on carcass traits is related to the weight of a substantial cut (ham, loin).Genotypes at loci CAST/RsaI and MYOG have a significant effect on the value of certain traits and parameters of meat quality and its technological value (genotype CAST on pH at 35 min and 2, 3, 24, 48, 96, 144 h post-mortem (pH₃₅, pH₂, pH₃, pH₂₄, pH₄₈, pH₉₆, pH₁₄₄, respectively), R₁ (IMP/ATP), electrical conductivity at 3 and 4 h post-mortem (EC₃, EC₄), technological yield of meat in curing and thermal processing (TY) and protein content in the muscle tissue, while genotype MYOG on pH₄₈, EC₃₅, EC₃, EC₂₄ and dry matter content).     

Influence of early pH decline on calpain activity in porcine muscle

This study investigated the influence of post-mortem pH decline on calpain activity and myofibrillar degradation. From 80 pigs, 30 Longissimus dorsi (LD) muscles were selected on the basis of pH values at 3 h post-mortem and classified into groups of 10 as fast, intermediate and slow pH decline. The rate of pH decline early post-mortem differed between the three groups, but the ultimate pH values were similar at 24 h. Calpain activity and autolysis from 1 to 72 h post-mortem were determined using casein zymography and studied in relation to myofibrillar fragmentation.     

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments. PRACTICAL APPLICATION: Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.     

Association of calpastatin gene polymorphisms and meat quality traits in pig

Calpastatin is associated with the rate of post mortem degradation of structural proteins due to the regulation of calpain activity. In the present research, the associations between polymorphisms within 6th intron of porcine CAST gene and several meat quality traits were analyzed. The CAST gene polymorphisms affected meat colour, pH, water holding-capacity (WHC) and texture parameters (toughness, firmness, cohesiveness, chewiness, and resilience) measured in longissimus dorsi and semimembranosus muscles. The analysis performed on the most numerous breeds maintained in Poland, suggested that the most interesting polymorphisms were CAST/HpaII and CAST/RsaI, which had the greatest effect on WHC regardless of the breed analyzed and had an effect on meat pH, firmness and toughness for most breeds. Interestingly, for almost all breeds, the significant effect of both mutations on intramuscular fat content (IMF) was detected. The provided data confirmed the use of CAST gene as a genetic marker in breeding programmes which allows performing a selection focussed on improving the quality of pork.     

Contribution of postmortem muscle biochemistry to the delivery of consistent meat quality with particular focus on the calpain system

Tenderness has been repeatedly reported as the most important quality aspect of meat. However, a number of studies have shown that a significant portion of retail meat can be considered tough. As a consequence, a significant consumer segment is willing to pay a premium for guaranteed tender meat. However, apart from measuring the shear force, there is no reliable method to predict tenderness. Most of the branded meat programs therefore attempt to ensure eating quality by controlling some of the factors that affect tenderness. Meat tenderness is determined by the amount and solubility of connective tissue, sarcomere shortening during rigor development, and postmortem proteolysis of myofibrillar and myofibrillar-associated proteins. Given the effect of postmortem proteolysis on the muscle ultrastructure, titin and desmin are likely key substrates that determine meat tenderness. A large number of studies have shown that the calpain proteolytic system plays a central role in postmortem proteolysis and tenderization. In skeletal muscle, the calpain system consists of at least three proteases, μ-calpain, m-calpain and calpain 3, and an inhibitor of μ- and m-calpain, calpastatin. When activated by calcium, the calpains not only degrade subtrates, but also autolyze, leading to loss of activity. m-Calpain does not autolyze in postmortem muscle and is therefore not involved in postmortem tenderization. Results from a number of studies, including a study on calpain 3 knockout mice, have shown that calpain 3 is also not involved in postmortem proteolysis. However, a large number of studies, including a study on μ-calpain knockout mice, have shown that μ-calpain is largely, if not solely, responsible for postmortem tenderization. Research efforts in this area should, therefore, focus on elucidation of regulation of μ-calpain activity in postmortem muscle. Discovering the mechanisms of μ-calpain activity regulation and methods to promote μ-calpain activity should have a dramatic effect on the ability of researchers to develop reliable methods to predict meat tenderness and on the meat industry to produce a consistently tender product.     

Mitochondrial respiratory activity in porcine longissimus muscle fibers of different pig genetics in relation to their meat quality

The pig genetics of Duroc, Pietrain (MHS homozygote negative, PiNN), Pietrain (MHS homozygote positive, PiPP) and a F2-Duroc-Pietrain cross-breed were analyzed. The animals had comparable (P > 0.05) carcass weights, but the PiPP pigs had higher carcass yield and lean meat values (P < 0.05). Considering the meat quality characteristics, the PiPP showed a faster pH drop and higher electrical conductivity, drip loss, shear force as well as lightness and redness values (P < 0.05). The PiPP animals had less slow-twitch-oxidative (STO) and more fast-twitch-glycolytic (FTG) muscle fibers, whereas the results of the Duroc animals were converse (P < 0.05). The STO and FTG fibers of the PiPP animals were larger than those of the other genetics (P < 0.05). The analysis of the mitochondrial respiratory activity (MRA) using permeabilized longissimus muscle fibers resulted in no differences between the pig genetics before and immediately after slaughter. During chilling the MRA decreased in all pigs but to a higher extent in the PiPP pigs (P < 0.05).     

Sensory evaluations of porcine longissimus dorsi muscle: Relationships with postmortem meat quality traits and muscle fiber characteristics

The objective of this study was to investigate sensory evaluations and their relationships with meat quality measurements and histochemical characteristics in both fresh and cooked pork. Based on the results, postmortem meat quality traits were closely related to almost all the evaluated sensory attributes. With regard to histochemical characteristics, muscle fiber area was related to both fresh- (r = 0.18, P < 0.05) and cooked-meat color (r = −0.24, P < 0.01) as well as abnormal flavor intensity (r = 0.25, P < 0.01), and muscle fiber composition was associated with fresh pork color and taste acceptability after cooking. There were no significant relationships (P > 0.05) between type IIa muscle fiber content and the evaluated sensory attributes; however, good meat sensory quality was partially explained by the percentage of type I fiber.     

Effects of variation in porcine MYOD1 gene on muscle fiber characteristics, lean meat production, and meat quality traits

Three single nucleotide polymorphisms (SNPs) in the porcine MYOD1 gene were used for association analysis and haplotype construction to evaluate the effects of their substitution. Four hundred and three pigs of Yorkshire and Berkshire breeds were used. The mRNA expression levels of MYOD1 were examined. The g.489C>T and g.1264C>A SNPs were significantly associated with several muscle fiber characteristics, the loin eye area, and lightness. Particularly, animals having hetero-genotypes of both sites showed good performance both in lean meat production and meat quality traits. The results of haplotype substitution were similar to the associations of individual SNPs. Moreover, the 2 SNPs had significant effects on mRNA expression. Therefore, the g.489C>T and g.1264C>A SNPs in MYOD1 may be meaningful DNA markers that can be used for improving important porcine economic traits.     

Effect of the insulin-like growth factor-II and RYR1 genotype in pigs on carcass and meat quality traits

Recently, a new QTN (quantitative trait nucleotide), which is located in the regulatory sequence of the imprinted IGF-II gene was discovered in the pig and is associated with a significant increase in IGF-II mRNA expression in skeletal muscle during postnatal growth. The aim of the current study was to investigate the effect of the IGF-II paternal allele (Apat and Gpat animals that inherited, respectively, the mutant and wild type paternal allele of interest) on carcass and meat quality traits in Nn and NN RYR1 genotypes. A total of 141 animals were measured, almost equally distributed over the IGF-II and RYR1 genotypes and gender. The Apat allele increased carcass lean meat percentage with approximately 4.5% (P < 0.001) as a result of decreased backfat thickness. Average live weight daily gain was not affected, hence average daily lean meat gain was significantly higher for Apat compared to Gpat animals. The IGF-II mutation had no noticeable effect on meat quality in contrast with the RYR1 mutation. No interaction effects of both mutations on meat quality were noticed.     

Effects of muscle cortisol concentration on muscle fiber characteristics, pork quality, and sensory quality of cooked pork

The effect of muscle cortisol concentration on muscle fiber characteristics and technological and sensory quality of pork was investigated. With the exception of the percentage of type IIA fibers, muscle fiber characteristics were not associated to cortisol levels. However, muscle cortisol concentration was positively associated with muscle pH(24h) (r = 0.23, P<0.05) and negatively associated with drip loss (r = -0.49, P<0.001), lightness (r = -0.24, P<0.05), shear force (r = -0.25, P<0.05), and texture profile analysis-hardness (r = -0.35, P<0.01). Additionally, the water-holding capacity of meat samples was affected by cortisol levels, with lower cortisol concentrations associated with less tender samples. These results indicate that the concentration of cortisol in the muscle is related with meat quality as well as the sensory quality of cooked pork.     

Influence of dietary oils and protein level on pork quality. 1. Effects on muscle fatty acid composition, carcass, meat and eating quality

This study evaluated the effects of three dietary oils - palm kernel (PKO), palm (PO) and soyabean (SBO) - and two protein levels - high (HP) and low (LP) in a 3×2 factorial design involving 60 pigs on growth performance, muscle fatty acid composition and content, carcass, meat and eating qualities. Oil type did not have a significant effect on growth and carcass quality. PKO significantly reduced the polyunsaturated (PUFA) to saturated (SFA) fatty acid (P:S) ratio in longissimus muscle (P<0.001). PKO increased the concentrations of lauric (12:0), myristic (14:0), palmitic (16:0) and stearic (18:0) fatty acids and decreased linoleic acid (18:2). The LP diet increased intramuscular fat (IMF) from 1.7g/100g muscle in HP to 2.9g/100g (P<0.001), increased tenderness by 0.6 units (P<0.01) and juiciness by 0.5 units (P<0.01) on the 1-8 scale, but at the expense of lower daily weight gain (P<0.01), lower feed conversion efficiency (P<0.01), reduced P:S ratio (P<0.001) and increased lipid oxidation (P<0.01). The results suggest that PKO and PO could be used in tropical developing countries as cheaper alternatives to SBO for the production of good quality and healthy pork, but their limits of inclusion need to be determined.     

Effect of pre-rigor temperature incubation on sarcoplasmic protein solubility,calpain activity and meat properties in porcine muscle

The aim of the study was to investigate the effect of pre-rigor temperature incubation on sarcoplasmic protein characteristics in relation to meat properties within porcine muscle. Porcine Longissimus dorsi muscles were incubated at temperatures of 0, 10, 20, 30 and 40 °C to 6 h post mortem. Incubation at 40 °C induced a significant decrease of sarcoplasmic protein solubility and an increase in proteins in the myofibrillar fraction. The protein relocation was followed till 72 h post mortem but had largely been completed by the end of the temperature incubation at 6 h. SDS-PAGE and Western blot analyses suggested that phosphorylase and creatine kinase precipitated onto the myofilaments during incubation at 40 °C. Drip loss increased following incubation at 40 °C, indicating that the precipitation of phosphorylase and creatine kinase may be a factor of reduced water-holding capacity at the combination of high temperature and low pH. Incubation at 40 °C resulted in substantially lower shear force in parallel with loss of extractable activity of μ- and m-calpain, suggesting a rapid activation of both enzymes at high temperatures and low pH early post mortem.     

Skeletal muscle fiber type and myofibrillar proteins in relation to meat quality

Although numerous studies have reported the relationships among muscle fiber characteristics, lean meat content and meat quality, controversial perspectives still remain. Conventional histochemical classifications may be involved in a high level of error, subjectivity and it could not clearly explain variety of myofibrillar protein isoforms. Therefore, more information is needed on how different factors, such as species, breeds, gender, nutrient conditions, physiological state of animals, and environment factors, affect ultimate meat quality in order to evaluate these uncertainness. Unfortunately, there is little information that completely covers with relationship among the muscle fiber types, myofibrillar proteins and enzymatic proteolysis. In addition to the perspective of postmortem metabolism, protein quality control in skeletal muscle and proteolytic degradation of muscle proteins during postmortem period could help to clarify this relationship. Therefore, the present review will focus on muscle fiber types, typing methods, muscle proteins and meat quality, and will summarize aspects of enzymatic view of proteasome.     

Association of PPARGC1A and CAPNS1 gene polymorphisms and expression with meat quality traits in pigs

This study aimed to investigate the genes PPARGC1A (peroxisome proliferator-activated receptor gamma-coactivator 1A) and CAPNS1 (calpain small subunit 1) as candidate genes affecting meat quality traits in pigs. Four polymorphisms were identified in PPARCG1A and three in CAPNS1. The PPARGC1A polymorphism c.1288T>A was associated with pH and cooking loss in a F2 Duroc×Pietrain experimental cross (DuPi, n=313) and with pH values in Italian Large White (ILW, n=380) and Italian Landrace (ILA, n=158) populations (P<0.05). The CAPNS1 polymorphism c.429A>C was associated with pH and conductivity in DuPi and with meat color in ILA (P<0.05). PPARGC1A mRNA expression associated with drip loss (P<0.01) and the same tendency was found for CAPNS1 (P=0.06). The promoter methylation profiling suggested that methylation is not involved in CAPNS1 expression regulation. In conclusion, porcine PPARGC1A and CAPNS1 genes may affect meat quality traits, with breed-specific differences, and they could be used as markers for the improvement of meat quality in pigs.     

Effect of exercise on skeletal muscle proteolytic enzyme activity and meat quality characteristics in Iberian pigs

The effects of physical activity on performance, carcass traits, Psoas major lysosomal and exoprotease acitivies and meat quality were studied in 24 castrated male Iberian pigs during the last fattening period (from 111.1±SD: 5.2kg). Pigs were randomly distributed in three groups. Two groups receiving the same diet were reared in confinement, one housed in individual pens of 8m(2) (sedentary group) and the other was housed outdoor with daily (up to 2km) forced walking (exercise group). And one group was reared under the traditional production system walking daily several km and fed mostly with acorn from Quercus ilex and Quercus rotundifolia and grass (free-range group). No differences were found in performance and carcass traits. In exercised pigs a lower activity of cathepsin B+L and total cathepsins (P<0.05) was observed. Exercise induced the inhibition of dipeptidyl peptidases II and III and arginyl aminopeptidase and the activation of dipeptidyl peptidases IV and leucyl aminopeptidase (P<0.05). Although no effects on total free amino acids in Psoas major muscle were observed the concentration of branched chain amino acids decreased in the free-range pig group probably related to an increase in physical activity. Exercise had no effects in Psoas major postmortem tenderness and water holding capacity.     

Association and expression analysis of porcine HNF1A gene related to meat and carcass quality traits

The aim of this study was to investigate the association and expression of HNF1A gene as a candidate gene for meat and carcass quality traits in pigs. Statistical analysis revealed that the g.8260 A>G polymorphism significantly associated with pH 24_H, meat percentage and muscle area in the F₂ Duroc × Pietrain (DuPi, n = 313) and with pH 24_L, fat area and backfat thickness in the Pietrain (Pi, n = 110) population. HNF1A mRNA and protein expressions were higher (p < 0.05) in animals with the low post-mortem muscle pH 24_L. The promoter methylation profiling suggested that methylation was not involved on HNF1A expression regulation (p > 0.05) in animal with divergent muscle pH. In conclusion, polymorphism in porcine HNF1A gene could be used as a candidate marker to improve the meat and carcass quality traits, with the consideration of breed-specific effect.     

Early post-mortem sarcoplasmic proteome of porcine muscle related to lipid oxidation in aged and cooked meat

In order to identify specific markers of lipid oxidation generated in meat during refrigerated storage and cooking an analysis was conducted to investigate the relationships between the early post-mortem sarcoplasmic proteome, which contains the majority of enzymes involved in the oxidative process, and the level of lipid oxidation. This study was performed in Longissimus lumborum pig muscle. Proteome was analysed by 2-D electrophoresis in combination with liquid chromatography–tandem mass spectrometry (LC–MS/MS) and lipid oxidation was estimated by the TBA reactive substances (TBA-RS) measurement. Many markers of lipid oxidation were identified, but no single marker covered the oxidative process in its entirety. The role of five protein groups (albumin, redoxins, annexins, lipid transporters and enzymes of aerobic respiration), from which a link with lipid oxidation can be established, is discussed. This study, which completes a precedent work focused on protein oxidation, clearly demonstrates that a combination of several markers is needed to assess the sensitivity of meat to oxidation during both ageing and cooking.     

The relation of blood glucose level to muscle fiber characteristics and pork quality traits

The purpose of this study was to examine the relationships between blood glucose level, muscle fiber characteristics, and pork quality. Muscle samples were classified into three groups based on blood glucose level measured at slaughter. Pigs with higher area percentages of fiber type IIB showed higher blood glucose levels compared to pigs with lower area percentages of fiber type IIB. The high blood glucose level group presented lower pH values at 45 min and 24 h postmortem, and also had higher L^∗ values and reduced water holding capacity. In addition, blood glucose level had a negative relationship with pH_45 min and the solubility of sarcoplasmic and myofibrillar proteins, whereas it had a positive relationship with drip loss and filter-paper fluid uptake. In conclusion, blood glucose level was related to muscle fiber area composition and could partially indicate ultimate pork quality.     

Association between polymorphisms of the heart fatty acid binding protein gene and intramuscular fat content,fatty acid composition,and meat quality in Berkshire breed

The objective of this study was to examine the relationship between polymorphisms of the heart fatty acid binding protein (H-FABP) gene and variation in intramuscular fat (IMF) content, fatty acid composition, and meat quality in Berkshire breed. We detected an association between IMF content and H-FABP HinfI restriction fragment length polymorphism (RFLP) genotype. The HH genotype showed the greatest IMF content among the genotype classes (P < 0.05). Regarding meat quality traits, only drip loss was significantly different among the H-FABP HinfI RFLP genotype classes (P < 0.01). In the case of fatty acid composition, the degree of saturation of fatty acids was greater in hh-genotype pigs than in HH and Hh genotypes. The H-FABP MspI RFLP genotype affected unsaturated fatty acid content, and the ratio of polyunsaturated fatty acid to saturated fatty acid (P < 0.05), whereas the H-FABP HaeIII RFLP genotype had no effect on fatty acid characteristics.