Autophagy during beef aging

Apoptosis and autophagy of muscle cell during pork postmortem aging

OBJECTIVE

Pork is an important source of animal protein in many countries. Subtle physiochemical changes occur during pork postmortem aging. The changes of apoptosis and autophagy in pork at 6 h to 72 h after slaughter were studied to provide evidence for pork quality.

METHODS

In this article, morphological changes of postmortem pork was observed through Hematoxylin-eosin staining, apoptotic nuclei were observed by TdT-mediated dUTP nick end labeling assay, protein related to apoptosis and autophagy expressions were tested by western blot and LC3 level were expressed according to immunofluorescence assay.

RESULTS

In this study, we found the occurrence of apoptosis in postmortem pork, and the process was characterized by nucleus condensation and fragmentation, formation of apoptotic bodies, increase in apoptosis-related Bax/Bcl-2 levels, and activation of caspases. Autophagy reached its peak between 24 and 48 h after slaughter, accompanied by the formation of autophagosomes on the cell membrane and expression of autophagy-related proteins beclin-1, P62, LC3-I, LC3-II, and ATG5.

CONCLUSION

Obvious apoptosis was observed at 12 h and autophagy reached its peak at 48 h. The present work provides the evidence for the occurrence of apoptosis and autophagy during postmortem aging of pork. In conclusion, the apoptosis and autophagy of muscle cells discovered in this study have important implications for pork in the meat industry.

Muscle Hypertrophy Is Linked to Changes in the Oxidative and Proteolytic Systems during Early Tenderization of the Spanish Breed "Asturiana de los Valles"

For fresh meat consumers, eating satisfaction is of utmost importance and tenderness is one of the most important characteristics in this regard. Our study examined beef of different animal biotypes of the autochthonous breed "Asturiana de los Valles" (AV) to determine if early postmortem oxidative and proteolytic processes may influence the final tenderness of the product. This meat-specialized breed shows different biotypes depending on the frequency of a myostatin mutation "mh" that induces double-muscling or muscular hypertrophy (mh/mh, mh/+, +/+). Samples from the longissimus dorsi muscles of yearling bulls were analyzed during the first 24 h postmortem. Changes in the redox balance of muscle cells were significant in the first hours after slaughter; total antioxidant activity was higher in the mh/mh biotype and it followed the shortening of the sarcomeres, a key parameter in understanding meat tenderness. The two proteolytic systems studied (proteasome and lysosome) followed distinct patterns. Proteasome activity was higher in the (mh/+) biotype, which correlated with higher protein damage. Lysosome proteolysis was increased in the more tender biotypes (mh genotypes). Autophagic activation showed significant differences between the biotypes, with (mh/mh) showing more intense basal autophagy at the beginning of the postmortem period that decreased gradually (p < 0.001), while in the normal biotype (+/+), it was slightly delayed and then increased progressively (p < 0.001). These results suggest that this type of catalytic process and antioxidant activity could contribute to the earlier disintegration of the myofibers, particularly in the mh/mh biotypes, and influence the conversion of muscle into meat.

Green tea catechin prevents oxidative stress-regulated autophagy and apoptosis signaling, and inhibits tenderness in postmortem bovine longissimus thoracis et lumborum muscle

Although green tea catechin has been reported to be an antioxidant and preservative in meat, the extent to which it affects the tenderization of bovine muscle remains largely unknown. This study seeks to evaluate the effect of catechin on the interplay between apoptosis and autophagy, and subsequently, the development of bovine muscle tenderness. The results indicate that catechin significantly alleviated oxidative stress. A concomitant reduction of autophagic markers LC3-II/LC3-I ratio, Beclin-1, and Atg7 levels were caused by catechin. Besides, aforementioned autophagy inhibition was further augmented by PI3K/Akt/mTOR activation. Additionally, catechin protected against mitochondrial dysfunction and inhibited mitochondria-dependent caspase apoptosis pathway. Furthermore, there was a reciprocal inhibition between autophagy and apoptosis. Ultimately, tenderness at 24 and 120 h, an increase in the gap between muscle fiber bundles, and disintegration of myofibrillar architectures were all inhibited by catechin. Therefore, despite alleviating oxidative stress, catechin may hamper tenderization pattern of postmortem bovine muscle.

Contribution of mitochondria to postmortem muscle tenderization: a review

Postmortem meat tenderization is a process mediated by a series of biochemical reactions related to muscle cell death. Cell death is considered a sign that muscle has started to transform into meat. Mitochondria play a significant role in regulating and executing cell death, as they are an aggregation point for many cell death signals and are also the primary target organelle damaged by tissue anoxia. Mitochondrial damage is likely to have an expanded role in postmortem meat tenderization. This review presents current findings on mitochondrial damage induced by the accumulation of reactive oxygen species during postmortem anaerobic metabolism and on the impact of mitochondrial damage on proteolysis and discusses how this leads to improved tenderness during aging. The underlying mechanisms of mitochondrial regulation of postmortem muscle tenderization likely focus on the mitochondria's role in postmortem cell death and energy metabolism. The death process of postmortem skeletal muscle cells may exhibit multiple types, possibly involving transformation from autophagy to apoptosis and, ultimately, necroptosis or necrosis. Mitochondrial characteristics, especially membrane integrity and ATP-related compound levels, are closely related to the transformation of multiple types of dead postmortem muscle cells. Finally, a possible biochemical regulatory network in postmortem muscle tenderization is proposed.

Role of the endoplasmic reticulum in the search for early biomarkers of meat quality

Defects in meat quality such as dark, firm and dry (DFD) beef have been related to high levels of oxidative stress that produce cellular alterations that may affect to the process of meat quality acquisition. Despite the important role of endoplasmic reticulum (ER) in the cellular response to oxidative stress, its function in the muscle-to-meat conversion process has not yet been studied. In this study, differences in muscular antioxidant defense and the unfolded protein response (UPR) of the ER in CONTROL (normal pH₂₄) and dark, firm, and dry (DFD, pH₂₄ ≥ 6.2) beef at 24 h post-mortem were analyzed to understand the changes in the muscle-to-meat conversion process related to meat quality defects. DFD meat showed poor quality, lower antioxidant activity (P < 0.05) and higher UPR activation (P < 0.05), which indicates higher oxidative stress what could partly explain the occurrence of meat quality defects. Therefore, the biomarkers of these cellular processes (IRE1α, ATF6α, and p-eIF2α) are putative biomarkers of meat quality.

Apoptosis Inducing Factors Involved in the Changes of Flesh Quality in Postmortem Grass Carp (Ctenopharyngodon idella) Muscle

Alterations of apoptosis have notable influences on flesh quality, but the mechanism is still unclear. Thus, apoptotic behaviors and related triggering mechanisms need to be explored. Fish muscle was prepared and stored at 4 °C for 0, 24, 48, 72, 96, and 120 h for apoptosis analysis. Results showed that positive apoptotic nuclei were positively correlated with drop loss and negatively correlated with shear force and water holding capacity (p < 0.05). Results showed that the triggering apoptotic mechanisms were involved with enhanced transcriptional levels of caspase-2, 3, 7, 8, and 9 through mitochondria and death receptor pathways in the muscle of grass carp. The decreased ATP content, changed cytochrome c redox state, increased protein levels of HSP27 and HSP 90, and enhanced activity of cathepsin (B, L, and D), calpain, and serine proteinase were involved in apoptosis activations. Results indicated that caspases, energy metabolism, cytochrome c redox state, heat shock protein expressions, and protease activities played critical roles in apoptosis alterations in carp muscle during refrigerated storage.

Inflammaging: Implications in Sarcopenia

In a world in which life expectancy is increasing, understanding and promoting healthy aging becomes a contemporary demand. In the elderly, a sterile, chronic and low-grade systemic inflammation known as "inflammaging" is linked with many age-associated diseases. Considering sarcopenia as a loss of strength and mass of skeletal muscle related to aging, correlations between these two terms have been proposed. Better knowledge of the immune system players in skeletal muscle would help to elucidate their implications in sarcopenia. Characterizing the activators of damage sensors and the downstream effectors explains the inference with skeletal muscle performance. Sarcopenia has also been linked to chronic diseases such as diabetes, metabolic syndrome and obesity. Implications of inflammatory signals from these diseases negatively affect skeletal muscle. Autophagic mechanisms are closely related with the inflammasome, as autophagy eliminates stress signaling sent by damage organelles, but also acts with an immunomodulatory function affecting immune cells and cytokine release. The use of melatonin, an antioxidant, ROS scavenger and immune and autophagy modulator, or senotherapeutic compounds targeting senescent cells could represent strategies to counteract inflammation. This review aims to present the many factors regulating skeletal muscle inflammaging and their major implications in order to understand the molecular mechanisms involved in sarcopenia.

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.

PSE condition is associated with increased apoptotic potential in broiler pectoralis major muscle

This study compared the meat quality and sensory quality characteristics of broiler pectoralis major (PM) muscle between meat quality classes, including reddish, firm, and non-exudative (RFN) and pale, soft, and exudative (PSE) conditions. Additionally, we also investigated the associations between the meat quality classes and expression levels of cytochrome c, initiator (caspase 9), and effector caspases (caspase 3 and 7) at the early postmortem period. A total of 135 PM muscles from broilers were used, and meat quality classes were determined according to the pH_{24 h} and lightness values and classified into the RFN (N = 81) and PSE (N = 54) conditions. The PSE breasts showed lower muscle pH_{15 min} and pH_{24 h} values compared to the RFN breasts (P < 0.05). A lower lightness value was observed in the RFN group compared to the PSE group (P < 0.001), whereas there were no significant differences in redness and yellowness between the groups (P > 0.05). The PSE group exhibited higher extent of water loss, including drip loss and cooking loss, compared to the RFN group (P < 0.05). For these reasons, samples from the RFN group required less force to breakdown the cooked meat with more moisture in the mouth after chewing compared to samples from the PSE group (P < 0.001); however, flavor intensity did not differ between the groups (P > 0.05). At 15 min postmortem, all apoptosis-related molecules, including cytochrome c, caspase 9, caspase 3, and caspase 7, were present at higher levels in the PSE group than in the RFN group (P < 0.05). These results indicated that higher apoptotic potentials were associated with the development of PSE chicken breasts. Therefore, the variation of meat quality in chicken breast can be explained as being affected by the expression levels of apoptosis-related factors at the early postmortem period.

Multi-responsive poly N-isopropylacrylamide/poly N-tert-butylacrylamide nanocomposite hydrogel with the ability to be adsorbed on the chitosan film as an active antibacterial material

Nanocomposite hydrogel composed of Poly N-isopropylacrylamide (PNIPAM), poly N-tert-Butylacrylamide (PBAM) and poly acrylic acid (PAA) was synthesized by free radical polymerization, and then thymol was embedded in it, to design an active antibacterial material that could control release. The characterization of products used SEM, AFM, FTIR, Zeta sizer to analyze the sensitivity of nanoparticles to pH, temperature and salt ions, and the agar diffusion method was used to determine the antibacterial effect of the polymers. The results showed that nanoparticles had pH, temperature and salt ion responsiveness, PNIPAM/PBAM (65:35) nanoparticles loaded thymol had longer release time (more than 24 h) at lower temperature than that (around 6 h) at high temperature. In addition, the nanoparticles could also be adsorbed on the chitosan film, which makes it have a wider range of applications. All thymol-loaded nanoparticles showed antibacterial activity against both B. subtilis and E. coli, while the chitosan film adsorbed nanoparticles showed weak effect, which was related to the controlled and slow release of bacteriostatic agents. Thus, these copolymers have potential value in the development and application of bacteriostatic packaging films for food.

Associations of Apoptotic and Anti-Apoptotic Factors with Beef Quality, Histochemical Characteristics, and Palatability of Hanwoo Longissimus thoracis Muscle

This study compared the meat quality, histochemical traits, palatability, and expression levels of apoptotic (cytochrome c and caspases) and anti-apoptotic (small heat shock proteins) factors at 45 min and 24 h post-mortem of Hanwoo Longissimus thoracis muscles in groups categorized by Warner-Bratzler shear force (WBS) values to investigate the association between beef tenderness variation and apoptosis-related molecules. There were no differences in marbling scores, meat quality traits, or histochemical characteristics among the WBS groups (p > 0.05) indicating no significant effect on the tenderness variation in the current study. On the other hand, the low group exhibited higher levels of apoptotic and anti-apoptotic factors (except for αβ-crystallin) at 45 min post-mortem compared to the high WBS group, resulting in higher scores of tenderness attributes (p < 0.05). However, the level of αβ-crystallin at 45 min post-mortem was lower in the low and medium WBS groups compared to the high WBS group (p < 0.0106). At 24 h post-mortem, no significant differences were observed in the expression levels of apoptosis-related factors among the WBS groups (p > 0.05) except for heat shock protein 27 (p < 0.05).

Effects of quercetin on tenderness, apoptotic and autophagy signalling in chickens during post-mortem ageing

The effect of quercetin on chicken breast muscle tenderness and the associated mechanism were investigated. The results indicated that quercetin significantly decreased the shear force and increased the myofibril fragmentation index (MFI). Haematoxylin-eosin-stained images showed that the internal structure of myofibril bundles in the quercetin-treated group was obviously degraded. Transmission electron microscopy showed that the myofibril structure, especially the M-line and A-band, was seriously degraded after quercetin treatment. Furthermore, quercetin treatment increased caspase-3 activity and the Bax/Bcl-2 ratio. The intensity of BiP, XBP1 and p-IRE1/IRE1 ratio increased significantly, and caspase-12 was activated. In addition, quercetin induced the transition from LC3I to LC3II and increased the expression of ATG7 and Beclin-1. The PI3K/Akt/mTOR signalling pathway was involved in the induction of autophagy and apoptosis by quercetin. These results indicated quercetin can promote meat tenderization, and activate apoptosis and autophagy pathways during post-mortem ageing.

Myostatin gene inactivation increases post-mortem calpain-dependent muscle proteolysis in mice

Myostatin deficiency leads to extensive skeletal muscle hypertrophy, but its consequence on post-mortem muscle proteolysis is unknown. Here, we compared muscle myofibrillar protein degradation, and autophagy, ubiquitin-proteasome and Ca²⁺-dependent proteolysis relative to the energetic and redox status in wild-type (WT) and myostatin knock-out mice (KO) during early post-mortem storage. KO muscles showed higher degradation of myofibrillar proteins in the first 24 h after death, associated with preserved antioxidant status, compared with WT muscles. Analysis of key autophagy and ubiquitin-proteasome system markers indicated that these two pathways were not upregulated in post-mortem muscle (both genotypes), but basal autophagic flux and ATP content were lower in KO muscles. Proteasome and caspase activities were not different between WT and KO mice. Conversely, calpain activity was higher in KO muscles, concomitantly with higher troponin T and desmin degradation. Altogether, these results suggest that calpains but not the autophagy, proteasome and caspase systems, explain the difference in post-mortem muscle protein proteolysis between both genotypes.

Autophagy in farm animals: current knowledge and future challenges

Autophagy (a process of cellular self-eating) is a conserved cellular degradative process that plays important roles in maintaining homeostasis and preventing nutritional, metabolic, and infection-mediated stresses. Surprisingly, little attention has been paid to the role of this cellular function in species of agronomical interest, and the details of how autophagy functions in the development of phenotypes of agricultural interest remain largely unexplored. Here, we first provide a brief description of the main mechanisms involved in autophagy, then review our current knowledge regarding autophagy in species of agronomical interest, with particular attention to physiological functions supporting livestock animal production, and finally assess the potential of translating the acquired knowledge to improve animal development, growth and health in the context of growing social, economic and environmental challenges for agriculture.Abbreviations: AKT: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ASC: adipose-derived stem cells; ATG: autophagy-related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BVDV: bovine viral diarrhea virus; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CMA: chaperone-mediated autophagy; CTSB: cathepsin B; CTSD: cathepsin D; DAP: Death-Associated Protein; ER: endoplasmic reticulum; GFP: green fluorescent protein; Gln: Glutamine; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; IF: immunofluorescence; IVP: in vitro produced; LAMP2A: lysosomal associated membrane protein 2A; LMS: lysosomal membrane stability; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MDBK: Madin-Darby bovine kidney; MSC: mesenchymal stem cells; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NBR1: NBR1 autophagy cargo receptor; NDV: Newcastle disease virus; NECTIN4: nectin cell adhesion molecule 4; NOD1: nucleotide-binding oligomerization domain 1; OCD: osteochondritis dissecans; OEC: oviduct epithelial cells; OPTN: optineurin; PI3K: phosphoinositide-3-kinase; PPRV: peste des petits ruminants virus; RHDV: rabbit hemorrhagic disease virus; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy.

Antemortem inhibition of phosphoinositide 3-kinase causes changes in meat quality traits in broiler chickens

Phosphoinositide 3-kinase (PI3K) is an enzyme that mediates endocrinological responses, such as intracellular signaling of insulin and growth factors, and plays important roles in muscle homeostasis and growth. In this study, the effect of antemortem PI3K activity on meat quality traits was investigated using broiler chickens whose PI3K was inhibited pharmacologically. Breast and thigh muscles were harvested from broilers treated with the PI3K inhibitor wortmannin, and meat quality traits were evaluated by determination of color, water-holding capacity, and breaking strength. The pH and concentrations of glycogen and free amino acids were also investigated as determinants of the chemical properties of meat. The results indicated that antemortem PI3K inhibition by wortmannin modified breast muscle color with lower L∗ values (P < 0.05) and b∗ values (P < 0.05) and higher a∗ values (P < 0.05). Antemortem PI3K inhibition also increased the water-holding capacity of breast muscles (P < 0.05), although breaking strength was not much affected. In addition, antemortem PI3K inhibition increased the concentrations of free amino acids in breast muscles, especially arginine (P < 0.05) and glutamic acid (P < 0.05). Similar effects were observed in thigh muscles. Lower glycogen levels at sacrifice (P < 0.05) and the resultant higher pH during the postmortem period (P < 0.05) were associated with PI3K inhibition-induced changes in meat quality traits. The wortmannin-treated muscles shared certain features with dark, firm, and dry meat which is a common abnormal meat. These findings suggest that antemortem PI3K activity contributes to meat quality traits and is involved in the molecular mechanism of the production of meat quality abnormalities.

Effect of the muscle nanostructure changes during post-mortem aging on tenderness of different beef breeds

Objective

Tenderness is a very complex feature, and the process of its formation is very complicated and not fully understood. Its diversification is one of the most important problems of beef production, as a result beef aging is widely used to improve tenderness as it is believed to provide a homogeneous product to consumers. While few studies have evaluated the muscle structure properties in relation to tenderness from early post-mortem, there little to no information available on how the muscle nanostructure of beef carcasses changes during post-mortem ageing to determine the appropriate aging time for acceptable tenderness.

Methods

Muscle nanostructure (myofibril diameter [MYD], myofibril spacing [MYS], muscle fibre diameter [MFD], muscle fibre spacing [MFS], and sarcomere length [SL]), meat tenderness and cooking loss [CL]) were measured on 20 A2 longissimus muscles of Bonsmara, Beefmaster, Hereford, and Simbra at 45_mins, 1, 3, and 7 days post-slaughter. Muscle nanostructure was measured using a scanning electron microscope, while tenderness was measured using Warner Bratzler shear force.

Results

At 45 minutes post-slaughter, breed affected MYD and MYS only, while at 24_hrs it also affected MFD and MFS. On day 3 breed effected MFS and SL, while on day 7 breed effected tenderness only. As the muscles matured, both MYD and MYS decreased while CL increased, and the muscles became tender. There was no uniformity on muscle texture features (surface structure, fibre separation, muscle contraction, and relaxation) throughout the ageing period.

Conclusion

Meat tenderness can be directly linked to breed related myofibril structure changes during aging in particular the MYD, spacing between myofibrils and their interaction; while the MFD, spacing between muscle fibres, SL, and CL explain the non-uniformity in beef tenderness.

Quantitative changes in peptides derived from proteins in beef tenderloin (psoas major muscle) and striploin (longissimus lumborum muscle) during cold storage

Peptides derived from whole proteins in beef tenderloin (M. psoas major, PM) and striploin (M. longissimus lumborum, LL) associated with meat quality and muscle fiber composition were identified and quantified during 21 days of aging. Peptide quantification revealed 40-43 proteins to be significantly degraded during all aging time, and these were mostly sarcoplasmic proteins. Cooking loss of both muscles was not changed by aging (P > 0.05), whereas Warner-Bratzler shear force and meat color were affected by aging. Sensory tenderness increased in PM after 14 days of aging (P < 0.05). PM had a higher type I fiber content, whereas LL had a higher type IIX fiber content (P < 0.05), resulting in differences in proteolysis during all aging periods tested. These findings improve our understanding of different biochemical and physicochemical changes in aged meat according to the muscle type.

Metabolomic Profiling of Bos taurus Beef, Dairy, and Crossbred Cattle: A Between-Breeds Meta-Analysis

Cattle breeds may differ substantially in their metabolism. However, the metabolomes of dairy and beef cattle are not well-known. Knowledge of breed-specific metabolic features is essential for biomarker identification and to adopt specific nutritional strategies. The muscle hypertrophy (mh), a beef cattle phenotype present in Asturiana de los Valles (AV) but absent in Asturiana de la Montaña (AM) and Holsteins, may underlie such differences. We compared the plasma metabolomes of Holstein, AV, AM, and crossbred cattle recipients selected for meta-analysis within an embryo transfer (ET) program. Blood samples were collected on day 0 (oestrus) and day 7 (prior to ET) (N = 234 samples × 2 days). Nuclear magnetic resonance quantified N = 36 metabolites in plasma, and more metabolic differences between breeds were found on day 0 (N = 19 regulated metabolites) than on day 7 (N = 5). AV and AM largely differed from Holstein cattle (N = 55 and 35 enriched metabolic pathways, respectively); however, AV and AM differed in N = 6 enriched pathways. Metabolic activity was higher in AV than in Holstein cattle, as explained in part by the mh phenotype. The metabolomic characterization of breeds facilitates biomarker research and helps to define the healthy ranges of metabolite concentrations.

Effect of animal mixing as a stressor on biomarkers of autophagy and oxidative stress during pig muscle maturation

The objective of this work was to study the postmortem evolution of potential biomarkers of autophagy (Beclin 1, LC3-II/LC3-I ratio) and oxidative stress (total antioxidant activity, TAA; superoxide dismutase activity, SOD and catalase activity, CAT) in the Longissimus dorsi muscle of entire male ((Large White×Landrace)×Duroc) pigs subjected to different management treatments that may promote stress, such as mixing unfamiliar animals at the farm and/or during transport and lairage before slaughter. During the rearing period at the farm, five animals were never mixed after the initial formation of the experimental groups (unmixed group at the farm, UF), whereas 10 animals were subjected to a common routine of being mixed with unfamiliar animals (mixed group at the farm, MF). Furthermore, two different treatments were used during the transport and lairage before slaughter: 10 pigs were not mixed (unmixed group during transport and lairage, UTL), whereas five pigs were mixed with unfamiliar animals on the lorry and during lairage (mixed group during transport and lairage, MTL). These mixing treatments were then combined into three pre-slaughter treatments - namely, UF-UTL, MF-UTL and MF-MTL. The results show that MF-UTL and MF-MTL increased significantly the muscle antioxidant defense (TAA, SOD and CAT) at short postmortem times (4 and 8 h; P<0.001), followed by an earlier depletion of the antioxidant activity at 24 h postmortem (P<0.05). We also found that mixing unfamiliar animals, both at the farm and during transport and lairage, triggers postmortem muscle autophagy, which showed an earlier activation (higher expression of Beclin 1 and LC3-II/LC3-I ratio at 4 h postmortem followed by a decreasing pattern of this ratio along first 24 h postmortem) in the muscle tissues of animals from the MF-UTL and MF-MTL groups, as an adaptive strategy of the muscle cells for counteracting induced stress. From these results, we propose that monitoring the evolution of the main biomarkers of autophagy (Beclin 1, LC3-II/LC3-I ratio) and muscle antioxidant defense (TAA, SOD, CAT) in the muscle tissue within the first 24 h postmortem may help the detection of animal stress and its potential effect on the postmortem muscle metabolism.