Effect of Guanidinoacetic Acid on Production Performance, Serum Biochemistry, Meat Quality and Rumen Fermentation in Hu Sheep

Guanidinoacetic acid (GAA) can effectively improve the metabolism of energy and proteins by stimulating creatine biosynthesis. We present a study exploring the impact of GAA on production performance, serum biochemistry, meat quality and rumen fermentation in Hu sheep. A total of 144 weaned male Hu sheep (body weight 16.91 ± 3.1 kg) were randomly assigned to four groups with three replicates of twelve sheep in each group. The diets were supplemented with 0 (CON), 500 (GAA-1), 750 (GAA-2) and 1000 mg/kg (GAA-3) of GAA (weight of feed), respectively. After a comprehensive 90-day experimental period, we discovered that the supplementation of GAA had a remarkable impact on various muscle parameters. Specifically, it significantly enhanced the average daily growth (ADG) of the animals and improved the shear force and fiber diameter of the muscle, while also reducing the drip loss and muscle fiber density. Furthermore, the addition of GAA to the feed notably elevated the serum concentrations of high-density lipoprotein cholesterol (HDL-C), total protein (TP) and globulin (GLB), as well as the enzyme activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Concurrently, there was a decrease in the levels of triglycerides (TG) and malondialdehyde (MDA) in the serum. In addition, GAA decreased the pH and the acetate-to-propionate ratio and increased the total volatile fatty acids (TVFA) and ammoniacal nitrogen (NH3-N) levels of rumen fluid. Additionally, GAA upregulated acetyl-CoA carboxylase (ACC) gene expression in the Hu sheep's muscles. In conclusion, our findings suggest that GAA supplementation not only enhances muscle quality but also positively affects serum biochemistry and ruminal metabolism, making it a potential candidate for improving the overall health and performance of Hu sheep.

Number of denatured rigor cross-bridges determines the intracellular volume shrinkage in porcine muscle fibre under PSE-inducing condition

Earlier onset of rigor mortis is a critical physiological progress occurring in the development of pale soft and exudative (PSE) meat. However, how rigor cross-bridges denature under different physiological conditions and their impacts on water-holding capacity remains unclear. To address this scientific question, we firstly established a method to quantify the extent of rigor cross-bridge denaturation using skinned fibres prepared from porcine longissimus thoracis et lumborum muscle. Effects of pH and temperature on the kinetics of rigor cross-bridge denaturation, actomyosin denaturation and shrinkage of muscle fibre were studied. We then manipulated the number of rigor cross-bridges before the denaturation condition was initiated (pH 5.5, 38 °C). Results suggested that the loss of water-holding capacity in PSE meat is determined by the number of denatured rigor cross-bridges. Physiochemical analysis on myofibrils demonstrated that increase in protein oxidation, surface hydrophobicity and loss of electrostatic repulsive force between myofibrils may be involved in the mechanism.

Study on the Correlations between Quality Indicators of Dry-Aged Beef and Microbial Succession during Fermentation

Dry-aged beef has been long favored by people due to its unique flavor and taste. However, the inner relationship between its overall quality formation and microbial changes during dry aging has not yet received much attention and research. To deeply reveal the forming mechanism of the unique flavor and taste of dry-aged beef, correlations between its three main quality indicators, i.e., texture, free amino acids (FAAs), volatile flavor compounds (VFCs), and microbial succession were analyzed in this study. The results showed that Staphylococcus spp. and Macrococcus spp. were key strains that influenced the total quality of dry-aged beef and strongly correlated with chewiness, hardness, and sweet FAAs (Ala), providing beef with unique palatability and taste. Additionally, among VFCs, Staphylococcus spp. and Macrococcus spp. showed a strong correlation with octanal and heptanal, and meanwhile, those highly correlated with nonanal, pentanol, and oct-1-en-3-ol were Debaryomyces spp., Psychrobacter spp., and Brochothrix spp., respectively, providing beef with a unique flavor. Staphylococcus spp. was proposed to be the dominant genus for dry-aged beef. This study provides valuable reference for the understanding of the role of microorganisms involved in dry aging.

Heat/Cold Stress and Methods to Mitigate Its Detrimental Impact on Pork and Poultry Meat: A Review

This paper aims to provide an updated review and current understanding of the impact of extreme temperatures-focusing on heat stress (HS)-on the quality of pork and poultry meat, particularly amidst an unprecedented global rise in environmental temperatures. Acute or chronic HS can lead to the development of pale, soft, and exudative (PSE) meat during short transportation or of dark, firm, and dry (DFD) meat associated with long transportation and seasonal changes in pork and poultry meat. While HS is more likely to result in PSE meat, cold stress (CS) is more commonly linked to the development of DFD meat. Methods aimed at mitigating the effects of HS include showering (water sprinkling/misting) during transport, as well as control and adequate ventilation rates in the truck, which not only improve animal welfare but also reduce mortality and the incidence of PSE meat. To mitigate CS, bedding on trailers and closing the tracks' curtains (insulation) are viable strategies. Ongoing efforts to minimize meat quality deterioration due to HS or CS must prioritize the welfare of the livestock and focus on the scaleup of laboratory testing to commercial applications.

Pork muscle profiling: pH and instrumental color of the longissimus thoracis is not representative of pH and instrumental color of shoulder and ham muscles

From a population of 351 pork carcasses, 3.0-cm thick chops from the 10th rib location of the longissimus thoracis, faced surfaces of the triceps brachii and serratus ventralis muscles from the boneless shoulder, and faced surfaces of the biceps femoris, semitendinosus, semimembranosus, adductor, rectus femoris, and vastus lateralis muscles from the boneless ham were evaluated for pH and instrumental color (Minolta CR-400). Evaluations were conducted for at least three different locations on each of the muscle samples and averaged before data analysis occurred. The longissimus thoracis had the lowest pH and the lightest and least red color compared with the other eight muscles evaluated in this study (mean differences ranged from 0.98 to 8.70 for L*, 3.98 to 12.56 for a*, and 0.026 to 0.409 for pH). Furthermore, regression analysis suggested that pH and color values for the longissimus thoracis were not adequate predictors for pH and color values obtained from other muscles and therefore consideration should be given to the individual muscles that are of interest.

Towards the use of on-farm slaughterhouse

Slaughter on the farm can address the concerns of farmers by meeting the needs of short distribution channels while better preserving animal welfare and meat quality. It can support conventional slaughter, by compensating for the significant decrease in the number of slaughterhouses in recent decades. The review describes first the different stages of slaughter and their possible impacts on animals' stress, welfare and consequences on their meat quality. The second part takes stock of recent thinking on the subject of slaughter and the regulation and technological advances that have led to the development of mobile slaughter units. A non-exhaustive list of mobile slaughter units currently in use in different countries is presented. Although these units can only absorb a small percentage of the total amounts of animals slaughtered, they are a welcome alternative to current slaughter practices for certain types of production and distribution, provided that the animal welfare and all aspects of meat quality are garanteed.

Aging mechanism for improving the tenderness and taste characteristics of meat

Tenderness and taste characteristics of meat are the key determinants of the meat choices of consumers. This review summarizes the contemporary research on the molecular mechanisms by which postmortem aging of meat improves the tenderness and taste characteristics. The fundamental mechanism by which postmortem aging improves the tenderness of meat involves the operation of the calpain system due to apoptosis, resulting in proteolytic enzyme-induced degradation of cytoskeletal myofibrillar proteins. The improvement of taste characteristics by postmortem aging is mainly explained by the increase in the content of taste-related peptides, free amino acids, and nucleotides produced by increased hydrolysis activity. This review improves our understanding of the published research on tenderness and taste characteristics of meat and provides insights to improve these attributes of meat through postmortem aging.

Protein Phosphorylation Induced by Pyruvate Kinase M2 Inhibited Myofibrillar Protein Degradation in Post-Mortem Muscle

Myofibrillar protein degradation is primarily related to meat tenderness through protein phosphorylation regulation. Pyruvate kinase M2 (PKM2), a glycolytic rate-limiting enzyme, is also regarded as a protein kinase to catalyze phosphorylation. The objective of this study was to investigate the relationship between myofibrillar protein degradation and phosphorylation induced by PKM2. Myofibrillar proteins were incubated with PKM2 at 4, 25, and 37 °C. The global phosphorylation level of myofibrillar proteins in the PKM2 group was significantly increased, but it was sensitive to temperature (P < 0.05). Compared with 4 and 25 °C, PKM2 significantly increased the myofibrillar protein phosphorylation level from 0.5 to 6 h at 37 °C (P < 0.05). In addition, the degradation of desmin and actin was inhibited after they were phosphorylated by PKM2 when incubated at 37 °C. These results demonstrate that phosphorylation of myofibrillar proteins catalyzed by PKM2 inhibited protein degradation and provided a possible pathway for meat tenderization through glycolytic enzyme regulation.

Effect of sex (ram or wether) and short duration, high volt electrical stimulation on tenderisation of Longissimus thoracis et lumborum and Semimembranosus muscles derived from Boer Goat and large frame Indigenous Veld Goat

This study determined whether castration and electrical stimulation (ES) influenced chevon tenderness and related physiological characteristics in Boer Goat (BG; n = 36; 21 bucks and 15 wethers) and large frame Indigenous Veld Goat (IVG; n = 41; 21 bucks and 20 wethers). Half of buck and wether carcasses were ES (20s, 400 Volts peak, 5 ms pulses at 15 pulses/s) 10 min post-mortem. Dressed carcasses were chilled (4 °C within 1-h post-mortem). pH and temperature decline, % drip loss, sarcomere length (SL), myofibril fragmentation length (MFL; 1- and 4-days post-mortem), Calpain-1, -2 and calpastatin activities (1- and 24-h), Warner-Bratzler shear force (WBSF; 1-day post-mortem) and sensory attributes (tenderness and juiciness; 4-days post-mortem) were measured on Longissimus thoracis et lumborum (LTL) and Semimembranosus (SM) muscles. ES carcasses had significantly lower pH irrespective of sex or breed. Buck LTL and SM were less tender (P ≤ 0.05) supported by longer MFL and higher calpastatin activity (P < 0.05), than wether muscles. ES LTL were more tender (WBSF and sensory) (P ≤ 0.001) while ES SM were less affected (P = 0.055). ES caused lower Calpain-1 activity in the LTL. SL do not support cold shortening and calpastatin played a major role in the tenderisation of chevon early post-mortem. A longer ageing period is recommended for goat meat in general to achieve acceptable levels of tenderness.

Impact of chronic heat stress on behavior, oxidative status and meat quality traits of fast-growing broiler chickens

This research aimed to investigate, through a multifactorial approach, the relationship among some in-vivo parameters (i.e., behavior and blood traits) in broilers exposed to chronic HS, and their implications on proximate composition, technological properties, and oxidative stability of breast meat. A total of 300 Ross 308 male chickens were exposed, from 35 to 41 days of age, to either thermoneutral conditions (TNT group: 20°C; six replicates of 25 birds/each) or elevated ambient temperature (HS group: 24 h/d at 30°C; six replicates of 25 birds/each). In order to deal with thermal stress, HS chickens firstly varied the frequency of some behaviors that are normally expressed also in physiological conditions (i.e., increasing "drinking" and decreasing "feeding") and then exhibited a behavioral pattern finalized at dissipating heat, primarily represented by "roosting," "panting" and "elevating wings." Such modifications become evident when the temperature reached 25°C, while the behavioral frequencies tended to stabilize at 27°C with no further substantial changes over the 6 days of thermal challenge. The multifactorial approach highlighted that these behavioral changes were associated with oxidative and inflammatory status as indicated by lower blood γ-tocopherol and higher carbonyls level (0.38 vs. 0.18 nmol/mL, and 2.39 vs. 7.19 nmol/mg proteins, respectively for TNT and HS; p < 0.001). HS affected breast meat quality by reducing the moisture:protein ratio (3.17 vs. 3.01, respectively for TNT and HS; p < 0.05) as well as the muscular acidification (ultimate pH = 5.81 vs. 6.00, respectively; p < 0.01), resulting in meat with higher holding capacity and tenderness. HS conditions reduced thiobarbituric acid reactive substances (TBARS) concentration in the breast meat while increased protein oxidation. Overall results evidenced a dynamic response of broiler chickens to HS exposure that induced behavioral and physiological modifications strictly linked to alterations of blood parameters and meat quality characteristics.

Towards the discovery of goat meat quality biomarkers using label-free proteomics

This study aimed to identify for the first time protein biomarkers of meat quality traits from Longissimus thoracis (LT) muscle of goats (Capra hircus). Male goats of similar age and weight reared under extensive rearing conditions were used to relate the LT muscle proteome with multiple meat quality traits. The early post-mortem muscle proteome analyzed using label-free proteomics was compared among three texture clusters built using hierarchical clustering analysis. Twenty-five proteins were differentially abundant and their mining using bioinformatics revealed three major biological pathways to be involved: 10 muscle structure proteins (MYL1, MYL4, MYLPF, MYL6B, MYH1, MYH2, ACTA1, ACTBL2, FHL1 and MYOZ1); 6 energy metabolism proteins (ALDOA, PGAM2, ATP5F1A, GAPDH, PGM1 and ATP5IF1), and two heat shock proteins: HSPB1 (small) and HSPA8 (large). Seven other miscellaneous proteins belonging to pathways such as regulation, proteolysis, apoptosis, transport and binding, tRNA processing or calmodulin-binding were further identified to play a role in the variability of goat meat quality. The differentially abundant proteins were correlated with the goat meat quality traits in addition to multivariate regression models built to propose the first regression equations of each quality trait. This study is the first to highlight in a multi-trait quality comparison the early post-mortem changes in the goat LT muscle proteome. It also evidenced the mechanisms underpinning the development of several quality traits of interest in goat meat production along the major biochemical pathways at interplay. SIGNIFICANCE: The discovery of protein biomarkers in the field of meat research is an emerging topic. In the case of goat meat quality, very few studies using proteomics have been conducted with the aim of proposing biomarkers. Therefore, this study is the first to quest for biomarkers of goat meat quality using label-free shotgun proteomics with a focus on multiple quality traits. We identified the molecular signatures underlying goat meat texture variation, which were found to belong to muscle structure and related proteins, energy metabolism and heat shock proteins along with other proteins involved in regulation, proteolysis, apoptosis, transport and binding, tRNA processing or calmodulin-binding. We further evaluated the potential of the candidate biomarkers to explain meat quality using the differentially abundant proteins by means of correlation and regression analyses. The results allowed the explanation of the variation in multiple traits such as pH, color, water-holding capacity, drip and cook losses traits and texture.

Physicochemical Properties, Antioxidant Markers, and Meat Quality as Affected by Heat Stress: A Review

Heat stress is one of the most stressful events in livestock life, negatively impacting animal health, productivity, and product quality. Moreover, the negative impact of heat stress on animal product quality has recently attracted increasing public awareness and concern. The purpose of this review is to discuss the effects of heat stress on the quality and the physicochemical component of meat in ruminants, pigs, rabbits, and poultry. Based on PRISMA guidelines, research articles were identified, screened, and summarized based on inclusion criteria for heat stress on meat safety and quality. Data were obtained from the Web of Science. Many studies reported the increased incidences of heat stress on animal welfare and meat quality. Although heat stress impacts can be variable depending on the severity and duration, the exposure of animals to heat stress (HS) can affect meat quality. Recent studies have shown that HS not only causes physiological and metabolic disturbances in living animals but also alters the rate and extent of glycolysis in postmortem muscles, resulting in changes in pH values that affect carcasses and meat. It has been shown to have a plausible effect on quality and antioxidant activity. Acute heat stress just before slaughter stimulates muscle glycogenolysis and can result in pale, tender, and exudative (PSE) meat characterized by low water-holding capacity (WHC). The enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) act by scavenging both intracellular and extracellular superoxide radicals and preventing the lipid peroxidation of the plasma membrane. Therefore, understanding and controlling environmental conditions is crucial to successful animal production and product safety. The objective of this review was to investigate the effects of HS on meat quality and antioxidant status.

Relationship between pre-rigor temperature of pork longissimus muscle, myofibril-bound calpain activity and protein degradation

The effect of pre-rigor temperature incubation on the activity and distribution in sarcoplasmic and myofibrillar fractions of calpains, and meat quality attributes was investigated. Porcine longissimus thoracis muscles were incubated pre-rigor at 14, 22, 30 and 38 °C to 6 h postmortem, followed by another 2 h incubation at 14 °C. Thereafter, muscles were stored at 2 °C for 1 or 4 days. With higher pre-rigor temperature, sarcoplasmic Ca²⁺ concentration, purge loss and myofibril-bound calpain-1 content increased, while shear force declined. Water-holding capacity of isolated myofibrils was lower after pre-rigor incubation at 38 °C. Desmin and troponin T degradation, and myofibril fragmentation was greater upon incubation of isolated myofibrils with added Ca²⁺ in the order 800 μM Ca²⁺ > 40 μM Ca²⁺ > no Ca²⁺, suggesting that calpain-1 and calpain-2 were associated to myofibrils and proteolytically active with sufficient Ca²⁺. Activity of myofibril-bound calpain-1 in muscle incubated pre-rigor at 22 and 30 °C were higher than when incubated at 14 and 38 °C. These results indicate that calpains translocate from the sarcoplasm onto myofibrils with higher pre-rigor temperature to 30 °C and the proteolytic potential of myofibril-associated calpains is thereby increased.

Intracellular Calcium Overload and Activation of CaMKK/AMPK Signaling Are Related to the Acceleration of Muscle Glycolysis of Broiler Chickens Subjected to Acute Stress

The current study investigated the effect of preslaughter transport on stress response and meat quality of broilers and explored the underlying mechanisms involved in the regulation of muscle glycolysis through calcium/calmodulin-dependent protein kinase kinase (CaMKK)/AMP-activated protein kinase (AMPK) signaling. Results suggested that transport induced stress responses of broilers and caused PSE-like syndrome of pectoralis major muscle. Preslaughter transport enhanced the mRNA expressions of glycogen phosphorylase and glucose transporters, as well as the activities of glycolytic enzymes, which accelerated the breakdown of glycolytic substrates and the accumulation of lactic acid. In addition, acute stress induced abnormal intracellular calcium homeostasis by disrupting calcium channels on the cell membrane and sarcoplasmic reticulum, which led to the activation of CaMKK and promoted AMPK phosphorylation. This study provides evidence that the intracellular calcium overload and the enhancement of CaMKK/AMPK signaling are related to the accelerated muscle glycolysis of broiler chickens subjected to acute stress.

Effect of sodium bicarbonate on techno-functional and rheological properties of pale, soft, and exudative (PSE) meat batters

In the study, changes in salt-soluble protein (SSP) content, gel properties, rheological characteristic, and microstructure attributes of pale, soft, and exudative (PSE) pork batters with different concentrations of added sodium bicarbonate (0-0.6%) were investigated. The pH, b⁎ value, SSP content, cooking yield, texture properties, emulsion stability, and G' values at 72 °C significantly increased with the increase in sodium bicarbonate, but the texture properties and G' values of the samples with 0.4% and 0.6% did not significantly different, while the a⁎ value significantly decreased. Moreover, a greater G' value at 72 °C was in agreement with a higher hardness value of meat batter. The microstructure of cooked PSE meat batters with 0% and 0.2% sodium bicarbonate had a dense structure, and samples with 0.4% and 0.6% had some large cavities. In conclusion, the use of sodium bicarbonate can enhance the water holding capacity, texture and rheological properties of PSE meat batters by increasing their pH, SSP content, and emulsifying stability.

Physical properties during a 28-day ageing period of blesbok (Damaliscus pygargus phillipsi) Longissimus thoracis et lumborum and Biceps femoris muscles

The study aimed to determine the effect of sex, muscle-type, and ageing on the physical properties of blesbok (Damaliscus pygargus phillipsi) Longissimus thoracis et lumborum (LTL) and Biceps femoris (BF) muscles. Randomly assigned steak samples from twenty mature blesbok (10 of each sex) antelope were vacuum-packed and stored at 4.4 ± 1 °C for 2, 4, 7, 10, 17 and 28 ageing days. Cumulative purge loss, pH, colour (L*, a*, b), cooking loss, and Warner Braztler shear force were determined. Males had meat with higher (P = 0.032) pH values than females, while all other attributes were similar (P > 0.05). The LTL had greater (P < 0.05) purge losses, L* and a* values than the BF muscle, while other quality attributes were greater (P < 0.05) for the BF muscle. Despite fluctuations, there was an overall decrease in shear force with ageing time. According to all quality parameters measured, the optimum ageing period for blesbok would seem to be 10 days.

Effects of High Concentration Nitrogen Gas Stunning of Pigs on the Quality Traits of Meat and Small Intestine

The objective of present study was to investigate the feasibility of utilizing only high concentration of nitrogen gas in the stunning of pigs and its effects on the quality traits of the meat and small intestine.To conduct this experiment, three treatment groups were compared: (i) electric stunning (T1), (ii) CO2 (80%) gas stunning (T2), and (iii) N2 (98%) gas stunning (T3). A total of 21 standard pigs (Landrace × Yorkshire × Duroc; LYD) were collected from a commercial pig farm, randomly selecting seven pigs for each group (body weight of 104.5 to 120.6 kg). For stunning, each individual pig was separately kept in a gas chamber, after which each specific gas was used to fulfill the desired level in the pit. To obtain the desired level of concentration for each gas (N2 at 98% and CO2 at 80%), approximately 80 min and 35 min were required, respectively. It was observed that after reaching the desired level of concentration, pigs were stunned within a very short time (for CO2, 90 s and for N2, 120 s). For electric stunning, standard quality electric devices were used. After slaughtering, the meat and small intestine of each animal was collected separately and kept in a cool room where temperature was −2 °C. In the meat and small intestine, L* (Lightness) and b* (Yellowness) were high (p < 0.05) in the T1 and T3 groups. The T2 group showed high a* (Redness) (p < 0.05) values in both the meat and small intestine. A proximate composition of meat showed no significant differences except moisture. The water holding capacity (WHC), cooking loss (CL), and Warner-Bratzler shear force (WBSF) of meat were lowest in the T2 group, but not at a notable difference compared to T3. In the small intestine, L* (Lightness), a* (Redness), b* (Yellowness), and thickness significantly differed (p < 0.05) in each group, but WBSF showed no significance between the T2 and T3 groups. It is concluded that a high concentration of N2 gas (98%) may be considered in the stunning of pigs, and its effect on meat and small intestine is favorable.

Metabolic, proteomic and microbial changes postmortem and during beef aging

The purpose of this review is to provide an overview of the current knowledge about proteomic and metabolic changes in beef, the microbiological alteration postmortem and during aging, and observe the influence on beef quality parameters, such as tenderness, taste and flavor. This review will also focus on the different aging types (wet- and dry-aging), the aging or postmortem time of beef and their effect on the proteome and metabolome of beef. The Ca2+ homeostasis and adenosine 5'-triphosphate breakdown are the main reactions in the pre-rigor phase. After rigor mortis, the enzymatic degradation of connective tissues and breakdown of energy metabolism dominate molecular changes in beef. Important metabolic processes leading to the formation of saccharides, nucleotides, organic acids (e.g. lactic acid), creatine and fatty acids are considered in this context as possible flavor precursors or formers of beef flavor and taste. Flavor precursors are substrates for lipid oxidation, Strecker degradation and Maillard reaction during cooking or roasting. The findings presented should serve as a basis for a better understanding of beef aging and its molecular effects and are intended to contribute to meeting the challenges of improving beef quality.

Does Finishing at Pasture Influence the Colour of Muscle from Suckler Bulls and Can Colour Be Used to Authenticate Their Pre-Slaughter Diet?

The primary objective of this study was to compare the colour of muscle from bulls finished at pasture or indoors on a high concentrate diet. The ancillary objectives were to identify possible explanations for any differences in the colour observed and the potential of muscle colour to discriminate between bull beef from different production systems. Growth, longissimus muscle colour, fibre type composition and metabolic profile were measured in late-maturing breed sired suckler bulls slaughtered at 19 months of age after 199 days at pasture (G0), 100 days indoors after 98 days at pasture (G0AL) and indoors for 199 days (AL). When compared to bulls finished indoors and offered a high concentrate ration, the carcass weight of G0 bulls was lower, their carcasses were leaner, and their longissimus muscle was similar in lightness but less red and had a lower glycolytic metabolism. The temperature at which the longissimus muscle reached pH 6.0 was lower (19.7 °C) for G0 than for G0AL (29.9 °C) and AL (31.6 °C), which did not differ. Co-variate adjustment for this variable removed the differences in redness. Adjusting the chill settings appears to be a practical strategy for abattoirs to minimise early post-mortem differences in muscle colour between lighter grass-fed and heavier concentrate-fed carcasses. The preliminary results demonstrate the potential of both L*, a*, b* values and the visible reflectance spectra of muscle to discriminate between grass- finished and concentrate-finished bull beef, but further refinement and validation of the models is required.

Overexpression of Heat Shock Protein 70 Ameliorates Meat Quality of Broilers Subjected to Pre-Slaughter Transport at High Ambient Temperatures by Improving Energy Status of Pectoralis Major Muscle and Antioxidant Capacity

The induction of heat shock protein 70 (HSP70) potentially mediates meat-quality development under stress conditions. To investigate the effects and mechanism of HSP70 on the meat quality of the pectoralis major (PM) muscles of broilers exposed to pre-slaughter transport, a total of 168 broilers were intraperitoneally injected with L-glutamine (Gln) or saline. Twenty-four hours later, broilers were subjected to transport or held under normal living conditions. The results indicated that acute Gln supplementation significantly increased HSP70 expression in the PM of transported broilers (p < 0.05). The overexpression of HSP70 significantly alleviated the decreases in muscle pH and water-holding capacity and improved the shrinking of muscle fibers induced by transport (p < 0.05). HSP70 induction increased ATP content, decreased the activities of glycolytic enzymes, and lowered the phosphorylation level of AMP-activated protein kinase in transported broilers (p < 0.05). In addition, the overexpression of HSP70 greatly increased total superoxide dismutase and the total antioxidant capability and decreased the levels of reactive oxygen species, malonaldehyde, and carbonyls in the PM of transported broilers (p < 0.05). Overall, this work indicated that HSP70 could effectively improve the meat quality of transported broilers by improving the energy status, inhibiting glycolytic influx, and restoring redox homeostasis.

Acute stress deteriorates breast meat quality of Ross 308 broiler chickens by inducing redox imbalance and mitochondrial dysfunction

This study investigated the effects of acute stress on breast meat quality, redox status and mitochondrial function in pectoralis major (PM) muscle of broilers. A total of 168 broiler chickens (42-day-old, Ross 308) were randomly divided into control (CON) and pre-slaughter transport (T) treatments. A broiler was an experimental unit. Each treatment consisted of 84 broilers, and they were put in 12 crates with 7 broilers each. Broilers in the T group were transported according to a designed protocol, and the CON broilers were kept in crates under normal living conditions before slaughtering. Based on the meat quality traits assessed at postmortem 24 h, all PM muscles of the transported broilers were further classified into normal (T-NOR) and pale, soft and exudative (PSE)-like (T-PSE) groups for the determination of redox status in PM muscle and isolated mitochondria, energy metabolites, mitochondrial electron transport chain complexes activities, as well as mitochondrial function-modulating genes expression. Compared with CON, the extent of lipid peroxidation as well as protein oxidation were significantly increased in both PM muscles and mitochondria in T-PSE (P < 0.05), whereas not in T-NOR. Higher activities of glutathione peroxidase, total superoxide dismutase and Cu-Zn superoxide dismutase were observed in PM muscle of T-NOR broilers as compared with CON (P < 0.05). Pre-slaughter transport increased the generation of reactive oxygen species, as well as enhanced antioxidant capacity in PM mitochondria of broilers (P < 0.05). Compared with CON, the ATP content, activities of complex I and III, as well as relative mitochondrial membrane potential and swelling were significantly decreased in T-PSE (P < 0.05), whereas no significant changes in either ATP content or complex I activity were observed in T-NOR. Pre-slaughter transport enhanced the mRNA expression of regulators involved in the glutathione system, thioredoxin 2 system and mitochondrial biosynthesis in PM muscle of broilers (P < 0.05). Moreover, we noticed a more evident enhancement effect in T-NOR than in T-PSE (P < 0.05). Overall, this work indicates that acute stress-induced redox imbalance and mitochondrial dysfunction have significant implications for the development of PSE-like meat.

Comparison of chicken breast quality characteristics and metabolites due to different rearing environments and refrigerated storage

The objective of the present study was to compare the breast meat quality and metabolomic characteristics from broilers that were raised in conventional (conventional farm reared-broilers; CB, n = 20) and legally approved animal welfare farms (welfare farm reared-broilers; WB, n = 20) in aerobic cold storage (1, 3, 5, and 7 d). Compared to CB chickens, the WB chickens had a larger floor size as well as lower stocking density, atmospheric ammonia, and nipple-shared chicken counts. The results demonstrated significantly higher pH, L^⁎- and b^⁎-value, and lower shear force in CB compared to WB during cold storage. Using ¹H NMR analysis, 25 compounds were identified in the chicken breast meat. Partial least square-discriminant analysis (PLS-DA) was performed based on the identified metabolites. The content of 15 metabolites (1 di-peptide, 9 free amino acids, 2 glycolytic potential-related products, 2 nucleotide-related products, and 1 organic acid) was significantly different due to the rearing environment (CB vs. WB). Among them, all free amino acids were higher in CB than in WB. Six free amino acids (glycine, isoleucine, leucine, phenylalanine, valine, and β-alanine) had variable importance in projection (VIP) score >1, regardless of the number of cold storage days. Therefore, these compounds in the breast meat may be used as potential markers to determine the rearing environment of broilers. Also, this result might be an indication of stress-related meat quality changes in broilers.

Postmortem Muscle Protein Changes as a Tool for Monitoring Sahraoui Dromedary Meat Quality Characteristics

The effects of slaughter age (2 vs. 9 years) and postmortem time (6, 8, 10, 12, 24, 48 and 72 h) on the meat quality and protein changes of the longissimus lumborum muscles of the Algerian Sahraoui dromedary were investigated. Muscles of young dromedaries evidenced a slower acidification process and a significantly higher myofibrillar fragmentation index throughout the postmortem time. The SDS-PAGE of sarcoplasmic and myofibrillar proteins revealed that meat from young dromedaries was characterized by the lowest percentage of myoglobin (p < 0.001) and the highest percentage of desmin (p < 0.01). During postmortem time, a decrease was found for phosphoglucomutase (p < 0.01), α-actinin (p < 0.05) and desmin (p < 0.01) in meat from young dromedaries. Western blot revealed an intense degradation of troponin T in younger dromedaries, with an earlier appearance of the 28 kDa polypeptide highlighting differences in the proteolytic potential between dromedaries of different ages. Principal component analysis showed that meat from young dromedaries, starting from 24 h postmortem, was located in a zone of the plot characterized by higher levels of the myofibrillar fragmentation index, 30 kDa polypeptide and enolase, overall confirming greater proteolysis in younger animals. Data suggest that the investigation of the muscle proteome is necessary to set targeted interventions to improve the aging process of dromedary meat cuts.

Review: On-farm and processing factors affecting bovine carcass and meat quality

This paper reviews the current state of knowledge on beef carcass and meat quality, with particular emphasis on on-farm and processing factors associated with its high and inconsistent variability. The diversity of livestock systems comes from the diversity of breeds (dairy or beef), ages and gender (bulls, steers, heifers, cull cows) used to produce either mainly beef or beef and milk. In addition, there are factors linked to farming practices (including diet, especially grazing) which significantly influence the sensory, nutritional, technological and extrinsic (such as image) quality attributes of meat. These can become factors of positive differentiation when controlled by the application and certification of technical specifications. Finally, preslaughter (such as stress), slaughter (such as the chilling and hanging method of carcasses) and postslaughter (such as ageing, packaging and cooking) conditions have a strong influence on the microbiological, sensory, technological and image quality attributes of beef. In this review, potential synergisms or antagonisms between the different quality attributes are highlighted. For example, finishing cattle on grass, compared to indoor fattening on a high concentrate diet, has the advantage of producing leaner meat with a higher proportion of omega-3 fatty acids while exhibiting superior oxidative stability, but with the consequence of a darker meat colour and lower productivity, as well as higher seasonality and land surface requirements. Moreover, the control of on-farm factors is often guided by productivity (growth rate, feed conversion ratio) and carcass quality attributes (weight, conformation and fatness). Genetic selection has often been oriented in this direction, without taking other quality attributes into account. Finally, the interactions between all these factors (and especially between on-farm and slaughter or processing factors) are not considered in the quality grading schemes in European countries. This means that positive efforts at farm level may be mitigated or even eliminated by poor slaughtering or processing conditions. All these considerations explain why between-animal variability in quality can be high, even when animals come from the same farming system. The ability to predict the sensory and nutritional properties of meat according to production factors has become a major objective of the supply chain.

Denaturation manner of sarcoplasmic proteins in Pale, Soft and Exudative meat determines their positive impacts on myofibrillar water-holding capacity

The aim of the study was to investigate the denaturation manner of sarcoplasmic proteins (SP) under PSE condition to explain their positive impacts on water-holding compacity. We found that the SP precipitation under PSE-like condition (pH 5.5, 40 °C) and heating conditions (pH 5.5, 7.0, 8.0, 55 °C) were similar, but the myofibrillar water-holding capacity was improved only under PSE-like condition (pH 5.5, 40 °C). To understand the denaturation mechanism of SP, their physicochemical properties were examined. Results demonstrated that PSE-denaturation and heat-denaturation of SP were two different processes. At pH 7.0 and 8.0, the unfolding of SP due to temperature elevation did not alter the overall net surface negative charges but only increased hydrophobicity, whereas at pH 5.5, the net surface positive charges and hydrophobicity increased dramatically. We hypothesized that in PSE meat, denatured SP became highly positively charged and hydrophobic and easier to bind to the negatively charged MF, which is related to the improvement on water-holding capacity.

Acetylation inhibition alleviates energy metabolism in muscles of minipigs varying with the type of muscle fibers

In this study, we investigated whether preslaughter chemical-induced acetylation affected postmortem energy metabolism and pork quality. Thirty pigs were randomly assigned to control, acetyltransferase inhibitor (ATi) or deacetyltransferase inhibitor treatments. Serum, trapezius, longissimus lumborum, psoas major, semimembranosus and semitendinosus muscles were taken for analyses. The results indicated that ATi treatment significantly reduced the activities of lactate dehydrogenase and creatine kinase and heat shock protein 70 in serum (P < 0.05). ATi treatment increased ATP and glycogen content, but decreased lactic acid content in trapezius, psoas major and semitendinosus muscles (P < 0.05). A total of 13 acetylated proteins bands were identified and the deacetylation of creatine kinase may play a key role in slowing down the postmortem energy metabolism in ATi-treated group. In addition, ATi treatment reduced the rate of postmortem glycolysis in muscles with higher oxidative but lower glycolytic fibers. These findings provide a new insight into the underlying mechanism on muscle-specific postmortem changes of pork quality.

Effects of chilling duration on USDA Quality Grade of beef carcasses

Two hundred and nine beef carcasses (BW of 361 ± 53 kg) from crossbred, grain-finished cattle were harvested in a commercial abattoir and subjected to a 96-h spray chilling treatment, conducted at 0 to 3°C in a commercial hot box with a wind speed of 3.1 m/s and 153-lux of fluorescent light. At the 24, 48, 72, and 96 h points of the treatment, the carcasses were analyzed for fatty acid composition, marbling score, core temperature (n = 1), pH, shrinkage, color, and aerobic plate count (n = 50). Carcasses reached 3ºC after 12 to 16 h of chilling. There were minimal changes in shrinkage among time point (-0.4 to 1.2%; P ≤ 0.002), pH (5.56 to 5.69; P ≤ 0.001), and aerobic plate count (APC) (0.1 to 0.7 log; P ˂ 0.001). Initial 24-h grading revealed a grade composition of 21.1% Slight (SL, n = 44), 34.0% Small (SM, n = 71), 17.2% Modest (MT, n = 37), 17.7% Moderate (MD, n = 36), and 10.1% Slightly Abundant (SA, n = 21). With marbling score in numeric values between 200 (Practically Devoid00) and 1100 (Abundant00), carcasses that had SM or greater marbling score at 24 h experienced a deduction of 34 to 60 points by the 96th hour of spray chilling (P ≤ 0.042). Comparatively, the marbling scores of the SL carcasses increased from 442 points at 24 h to 469 points at 96 h. Moreover, SL carcasses had a greater percentage of polyunsaturated fats (PUFA) (P &lt; 0.001). Results indicate that spray chilling for 96 h may slightly increase the marbling score of USDA Select, but has minimal impacts on marbling score of greater USDA quality grades.

Morphological signs of myopathy in pork that show no drastic decrease in pH after slaughter

High pH value 45 minutes after slaughter (рН45) has so far been the most frequently used indicator to select pig carcasses with normal course of autolysis. However, in practice, this does not provide meat quality homogeneity. Therefore, carcasses with рН45 > 6.0 were examined for signs of myopathy, which are characteristic for PSE meat, using the histological method. To perform the study, we randomly selected 320 individuals for slaughter out of 1,059 individuals of mixed swine grown in the same conditions. After slaughter, we selected 18 fresh carcasses that demonstrated low рН45. The results of the examination of the muscular tissue (L. dorsi) samples revealed that pork varied in microstructural characteristics. Only 44% of the samples had no signs of myopathy: no contracture nodes and destructive changes in the muscle fibers were present. A total of 39% of the samples were identified to the muscular tissue with mildly expressed myopathy, 17% of the samples – to the muscular tissue with acute myopathy. Thus, among the carcasses with рН45 > 6.0, 56% of the carcasses had signs of mild and acute myopathy, which explains quality homogeneity of meat selected using this criterion. Statistical analysis of the results suggested that the increase in the diameter of the muscle fibers of glycolytic type was related to appearance of signs of mild and acute myopathy – “giant fibers”. Increase in the weight of animals is not a risk factor. The obtained results allowed us to conclude the necessity of developing new approaches to assessing meat quality immediately after the slaughter with the purpose of increasing efficiency in predicting technological properties of meat. Promising directions of developing quick methods in histology allow us to hope that such approaches may be based on the data on microstructure of fresh muscular tissue.

The effect of aging on beef taste, aroma and texture, and the role of microorganisms: a review

The present review summarizes the advantages and disadvantages of three different aging methods (traditional dry aging, wet aging in vacuum shrink pack and dry aging in a highly moisture-permeable bag), discusses the effects of aging on beef which focus on the formation of taste-active compounds and aroma-active compounds and texture changes, and speculates the role of microbes. All these three aging methods can improve the aroma, flavor and texture of beef to varying degrees. It is concluded that the improvement in the taste during aging may be attributed to the following three aspects: First, the release of reducing sugars from the transition of glycogen and ATP; Second, the formation of free amino acids (FAAs) and peptides through proteolysis; Third, IMP, GMP, inosine and hypoxanthine which are produced by the degradation of nucleotides. The improvement of aroma is related to the volatile aroma-active components, which are produced by the thermal oxidation/degradation of fatty acids and the Maillard reaction between amino acids and reducing sugars during aging. And the change of texture is mainly owing to the degradation of cytoskeletal myofibrin and collagen with intramural connective tissue in meat by the endogenous proteolysis system. The role of microorganism in aging will be the main direction of further research.

Techniques for postmortem tenderisation in meat processing: effectiveness, application and possible mechanisms

Abstract

Developing efficient and promising tenderising techniques for postmortem meat is a heavily researched topic among meat scientists as consumers are willing to pay more for guaranteed tender meat. However, emerging tenderising techniques are not broadly used in the meat industry and, to some degree, are controversial due to lack of theoretical support. Thus, understanding the mechanisms involved in postmortem tenderisation is essential. This article first provides an overview of the relationship of ageing tenderisation and calpain system, as well as proteomics applied to identify protein biomarkers characterizing tenderness. In general, the ageing tenderisation is mediated by multiple biochemical activities, and it can exhibit better palatability and commercial benefit by combining other interventions. The calpain system plays a key role in ageing tenderisation functions by rupturing myofibrils and regulating proteolysis, glycolysis, apoptosis and metabolic modification. Additionally, tenderising techniques from different aspects including exogenous enzymes, chemistry, physics and the combined methods are discussed in depth. Particularly, innovation of home cooking could be recommended to prepare relatively tender meat due to its convenience and ease of operation by consumers. Furthermore, the combined interventions provide better performance in controlled tenderness. Finally, future trends in developing new tenderising techniques, and applied consideration in the meat processing industry are proposed in order to improve meat quality with higher economical value.

Graphical abstract

An overview of health challenges in alternative poultry production systems

Due to consumer demand and changing welfare standards on health, ecology, equity, and safety concepts, poultry production has changed markedly over the past 20 y. One of the greatest changes to poultry production standards is now offering poultry limited access to the outdoors in alternative and organic poultry production operations. Although operations allowing access to the outdoors are still only a small portion of commercial poultry production, it may impact the gastrointestinal (GIT) health of the bird in different ways than birds raised under conventional management systems. The present review describes current research results in alternative systems by identifying how different poultry production operations (diet, environmental disruptive factors, diseases) impact the ecology and health of the GIT. Various research efforts will be discussed that illustrate the nutritional value of free-range forages and how forages could be beneficial to animal health and production of both meat and eggs. The review also highlights the need for potential interventions to limit diseases without using antibiotics. These alternatives could enhance both economics and sustainability in organic and free-range poultry production.

Dietary isoleucine improved flesh quality, muscle antioxidant capacity, and muscle growth associated with AKT/TOR/S6K1 and AKT/FOXO3a signaling in hybrid bagrid catfish (Pelteobagrus vachelli♀ × Leiocassis longirostris♂)

Background

Muscle is the complex and heterogeneous tissue, which comprises the primary edible part of the trunk of fish and mammals. Previous studies have shown that dietary isoleucine (Ile) exerts beneficial effects on growth in aquatic animals. However, there were limited studies regarding the benefits of Ile on fish muscle and their effects on flesh quality and muscle growth. Thus, this study was conducted to explore whether dietary Ile had affected flesh quality and muscle growth in hybrid bagrid catfish (Pelteobagrus vachelli♀ × Leiocassis longirostris♂).

Methods

A total of 630 hybrid fish, with an initial average body weight of 33.11 ± 0.09 g, were randomly allotted into seven experimental groups with three replicates each, and respectively fed seven diets with 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile/kg diets for 8 weeks.

Results

In the present study, we demonstrated that Ile significantly: (1) increased muscle protein and lipid contents and the frequency distribution of myofibers with ≤ 20 μm and ≥ 50 μm of diameter; (2) improved pH value, shear force, cathepsin B and L activities, hydroxyproline content, resilience, cohesiveness, and decreased cooking loss, lactate content, hardness, springiness, gumminess, and chewiness; (3) decreased reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl (PC) contents, GCLC and Keap1 mRNA levels, and up-regulated CuZnSOD, CAT, GPX1a, GST, and Nrf2 mRNA levels; (4) up-regulated the insulin-like growth factor 1, 2 (IGF-1, IGF-2), insulin-like growth factor 1 receptor (IGF-1R), proliferating cell nuclear antigen (PCNA), Myf5, Myod, Myog, Mrf4, and MyHC mRNA levels, and decreased MSTN mRNA level; (5) increased muscle protein deposition by activating AKT-TOR-S6K1 and AKT-FOXO3a signaling pathways.

Conclusion

These results revealed that dietary Ile improved flesh quality, which might be due to increasing nutritional content, physicochemical, texture parameters, and antioxidant ability; promoting muscle growth by affecting myocytes hyperplasia and hypertrophy, and muscle protein deposition associated with protein synthesis and degradation signaling pathways. Finally, the quadratic regression analysis of chewiness, ROS, and protein contents against dietary Ile levels suggested that the optimal dietary Ile levels for hybrid bagrid catfish was estimated to be 14.19, 12.36, and 12.78 g/kg diet, corresponding to 36.59, 31.87, and 32.96 g/kg dietary protein, respectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00572-4.

Effects of Algae Meal Supplementation in Feedlot Lambs with Competent Reticular Groove Reflex on Growth Performance, Carcass Traits and Meat Characteristics

There is growing interest in increasing omega-3 fatty acid (FA) contents in ruminant meat by means of dietary manipulation, but the effects of such manipulation on productive results and meat quality need to be ascertained. The aim of the present study was to assess the effects of supplementing lambs with competent reticular groove reflex (RGR) with marine algae as a source of omega-3 fatty acids on growth performance, carcass traits, and meat quality characteristics. Forty-eight feedlot lambs were distributed into three equal groups: the control group neither consumed marine algae nor had competent RGR, the second group received daily 2.5% of algae meal mixed in the concentrate, and the last group consumed the same amount of algae meal, but emulsified in a milk replacer and bottle-fed. Lambs in the second and third groups had competent RGR. There were not any negative effects on performance, carcass or meat quality parameters with algae supplementation. However, the results of the oxidative stability parameters were not conclusive. Ageing for 6 days improved meat tenderness and color, and increased lipid oxidation. In conclusion, algae meal inclusion in the diet of fattening lambs with competent RGR has no detrimental effects on animal performance, carcass traits or meat quality characteristics.

Indigenous Slaughter Techniques: Effects on Meat Physico-Chemical Characteristics of Nguni Goats

Simple Summary

In smallholder communal farming systems, Nguni people slaughter goats using indigenous methods which have cultural and spiritual significance to them. Nguni wethers were slaughtered using the transverse neck incision (TNI), suprasternal notch (SNP) and under the shoulder blade at the chest floor point of elbow piercing (CFP) to the direction of the heart to assess meat physico-chemical characteristics parameters. Nguni wethers slaughtered with the TNI and CFP methods produced meat with an acceptable appearance similar to goats slaughtered with the conventional standard procedures.

Abstract

To improve goat meat quality in rural communities, it is important to evaluate the effects of indigenous slaughter methods used by resource-limited farmers when performing traditional ceremonies on the meat physico-chemical characteristics. The current study assessed the effects of the meat physico-chemical characteristics of Nguni goats slaughtered with the transverse neck incision (TNI), suprasternal notch piercing (SNP) and the under shoulder blade piercing at the chest floor point of elbow (CFP) to the direction of the heart methods. Thirty Nguni weathers were randomly assigned to three slaughter treatments (10 goats/treatment). Musculus longissimus thoracis et lumborum (LTL) was sampled at post-mortem for physico-chemical characteristic measurements. Meat from wethers slaughtered with the SNP method had greater ultimate pH values than meat from wethers slaughtered with TNI and CFP slaughter methods. Wethers slaughtered with the SNP method had lower meat redness (a*), yellowness (b*), and chroma (C*) values than those slaughtered with TNI and CFP slaughter methods. Goat slaughter method did not affect meat drip loss, water holding capacity, cooking loss and shear force. Overall, Nguni wethers slaughtered with the TNI and CFP methods produced chevon with fresher meat appearance than those slaughtered using the SNP method.