Effects of halothane genotype and pre-slaughter treatment on pig meat quality. Part 1. Post mortem metabolism, meat quality indicators and sensory traits of m. Longissimus lumborum

Ractopamine does not rescue Halothane and Rendement Napole metabolism postmortem

The objective of this study was to determine if ractopamine (RAC) impacts postmortem muscle metabolism and subsequent pork quality in Halothane (HAL) and Rendement Napole (RN) mutant pigs. All RAC fed pigs had increased (P < 0.04) L* values. HAL and RN mutants muscle had lower (P < 0.01) pH values but RAC feeding had no effect. RN mutants had higher and lower (P < 0.05) muscle pH and temperatures, respectfully at 15 min and RN mutant pigs had greater (P < 0.0001) glycogen initially but lactate levels similar to wild type (WT) pigs at 24 h. RAC lowered (P < 0.05) glycogen in RN mutants but not in HAL mutated or WT pig muscle. These data show RAC feeding changes postmortem energy metabolism but does not change pH and pork quality hallmark of two major pig gene mutations and supports our contention that ultimate meat quality traits and their biochemical drivers may be more complex than originally reasoned.

Transcriptome-based analysis of early post-mortem formation of pale, soft, and exudative (PSE) pork

Pale, soft, and exudative (PSE) meat can cause consumer dissatisfaction and economic losses. This study determined meat quality, glycolytic enzyme activity, and differential gene expression in the longissimus lumborum (LL) and semimembranosus (SM) of normal and PSE pork carcasses. The SM did not result in PSE meat. Hexokinase, lactate dehydrogenase, and pyruvate kinase activities were lower in the SM of PSE carcasses than in the normal carcasses. Functional enrichment analysis revealed that immune, inflammatory, and muscle fibre genes were significantly enriched in PSE pork. More specifically, PPP1R3G and MSS51 may be key genes regulating pork quality in the SM. Meanwhile, the differential expression of PLVAB, ADIPOQ, LEP, MYH4, MYH7, MYL3, MYL6B, FOS, ATF3, and HSPA6 may induce PSE formation in the LL. These results may provide insights into PSE pork formation mechanisms and reveal candidate genes for improving meat quality after validation.

Effect of terminal sire line and timing second vaccination on effectiveness of immunocastration, performance, and carcass and meat quality

Performance (from 10 weeks until slaughter), carcass and meat quality, and effectiveness of immunocastration was compared in crossbred offspring of stress positive (BP+) and negative (BP-) Belgian Piétrain and Canadian Duroc (CD) given the second vaccination of Improvac® at different times (4, 6, 8 weeks before slaughter). CD offspring had a significantly higher daily gain (DG) and feed intake (DFI), and lower predicted lean meat percentage (LMP) and dressing yield compared to BP+ and BP-, while feed conversion ratio (FCR) did not differ. CD offspring had significantly lower drip loss and higher pH_i, intramuscular fat content than BP+ and BP- (except for pH_i). No significant effect of vaccination time on DG nor FCR was observed. Predicted LMP tended to increase as time-post injection decreased, while meat quality was minor affected. Earlier vaccination had no effect on the effectiveness of immunocastration based on testosterone and GnRH-binding.

Performance and carcass, loin and ham quality in crossbreds from three terminal sire lines

This study was designed to compare performance, carcass and meat quality of crossbred of a hybrid sow x three sire lines, i.e. stress positive Belgian Piétrain (BP), stress negative French Piétrain (FP) and Canadian Duroc (CD). BP offspring had a significantly higher carcass yield (p < .001) and lean meat content (p < .001) in comparison with FP, which was higher than CD. BP offspring had significantly lower pH (p < .05), water-holding capacity (WHC) (p < .001) and intramuscular fat (IMF) (p < .001) content in the loin compared to FP and CD, but these meat quality parameters, with the exception of pH, were superior for CD as compared to FP. In accordance with loin quality, pH_i, pH_u, WHC and IMF of BP were significantly lower (p < .05) compared to CD in the fresh and cooked ham. Most often, FP offspring could not be differentiated from the other offspring, with the exception of cooking loss of the cooked ham. Trained and consumer taste panels resulted in no significant differences (p > .1) in sensory attributes, however, consumers preffered CD based on ranking.

Study of the AMP-Activated Protein Kinase Role in Energy Metabolism Changes during the Postmortem Aging of Yak Longissimus dorsal

To explore the postmortem physiological mechanism of muscle, activity of adenosine monophosphate activated protein kinase (AMPK) as well as its role in energy metabolism of postmortem yaks were studied. In this experiment, we injected 5-amino-1-beta-d-furanonyl imidazole-4-formamide (AICAR), a specific activator of AMPK, and STO-609 to observe the changes in glycolysis, energy metabolism, AMPK activity, and AMPK gene expression (PRKA1 and PRKA2) in postmortem yaks during maturation. The results showed that AICAR could increase the expression of the PRKKA1 and PRKAA2 genes, activate AMPK and increase its activity. The effects of AICAR include a lower concentration of ATP, an increase in AMP production, an acceleration of glycolysis, an increase in the lactic acid concentration, and a decrease in the pH value. In contrast, STO-609 had the opposite effect. Under hypoxic adaptation, the activity of the meat AMPK increased, which accelerated glycolysis and metabolism and more effectively regulated energy metabolism. Therefore, this study lays the foundation for establishing a theoretical system of energy metabolism in postmortem yak meat.

Biochemical alterations in the Musculus triceps brachii and Musculus longissimus thoracis during early postmortem period in pigs

Muscle-to-meat-transition is influenced by alterations of the energy metabolism. Porcine Musculus triceps brachii (MT) consisted of more fast-twitch-glycolytic muscle fibers and samples, collected 0, 10 and 20 min after slaughter (p.m.), showed higher mitochondrial respiratory activities and ATP concentrations than Musculus longissimus thoracis (LT) samples. Enzyme activities in MT were higher at 0 min (glycogen phosphorylase (GP)), 10 min (GP, citrate synthase (CS)) and at 20 min p.m. (CS). However, LT results were higher at 0 min (lactate dehydrogenase (LDH)), 10 min (phosphofructokinase (PFK), LDH) and at 20 min p.m. (PFK, F₀F₁-ATPase (F₀F₁)). Between 0 min and 10 min p.m. CS activities decreased in LT and MT samples, PFK increased in LT and GP in MT samples. Between 10 min and 20 min p.m. PFK and LDH decreased in LT and GP in MT samples, whereas F₀F₁ increased in LT and CS in MT samples. The data indicate that muscles with different mitochondria contents show clearly different energy metabolism characteristics.

Polymorphism distribution of RYR1, PRKAG3, HFABP, MYF-5 and MC4R genes in crossbred pigs

This study was designed to screen the crossbred pigs for SNPs in five candidate genes, associated with pork quality traits and to differentiate their genotypes by PCR-RFLP. The results indicated that genotypes of crossbred pigs were NN (90%) and Nn (10%) for RYR1; RR (83%) and QR (17%) for PRKAG3; HH (98%), Hh (1%) and hh (1%) for HFABP; DD (99%) and CD (1%) for MYF-5; and AG (57%), GG (26%) and AA (17%) for MC4R SNPs, respectively. Allelic frequencies for five SNPs {RYR1 (1843C>T), PRKAG3 (c.599G>A), HFABP (c.1322C>T), MYF-5 (c.1205A>C) and MC4R (c.1426A>G)} were 0.95 and 0.05 (N/n), 0.08 and 0.92 (Q/R), 0.99 and 0.01 (H/h), 0.00 and 1.00 (C/D) and 0.45 and 0.55 (A/G), respectively. The effect of RYR1 (1843C>T) SNP was significant on pH₄₅ (P < 0.05), pH₂₄ (P < 0.05) and protein % (P < 0.05). The PRKAG3 (c.599G>A) and MC4R (c.1426A>G) SNP had significant association with dressing percentages. The results revealed that RYR1, PRKAG3 and MC4R SNPs may be used in marker associated selection for pork quality traits in crossbred pigs.

The effect of adenosine 5'-monophosphate (AMP) on tenderness, microstructure and chemical-physical index of duck breast meat

BACKGROUND

Adenosine 5'-monophosphate (AMP) is often used in meat and poultry soups as a flavor enhancer (flavor modifier), or as food additives for specific nutritional purposes. Our previous research as well as evidence from others showed that actomyosin could be dissociated into myosin and actin by AMP in extracted muscle solution. However, there is no report available on the application of AMP to dissociate actomyosin and to improve meat tenderness. The objectives of this study were to evaluate the effect of AMP on duck meat tenderness and other quality traits and to explore the mechanism of the action of AMP on meat tenderness.

RESULTS

Duck breast muscle was treated with 0, 10, 20, 30, 40 mmol L(-1) AMP at 5 °C for 10 h and examined for shear force, microstructure, actomyosin dissociation, myofibril fragmentation index (MFI), pH, water content, cooking loss, CIE* color (L*, a*, b*), inosine monophosphate (IMP) and free amino acid (FAA) contents. Results showed that shear force, cooking loss, L* and b* of the muscles significantly decreased after AMP treatment (P < 0.05); actomyosin dissociation, MFI, pH, water content, fiber diameter, sarcomere length, IMP and ammonia significantly increased (P < 0.05); no significant change in a* or other FAA content was observed (P > 0.05), and muscle shrinkage in transverse and longitudinal directions were restrained after AMP treatment.

CONCLUSION

The results suggest that AMP could notably improve meat tenderness, and this effect was probably mainly through increasing muscle pH, promoting actomyosin dissociation and disrupting the Z-line; meanwhile, the conversion of AMP to IMP may contribute to the flavor of meat.

Optimization of the Tenderization of Duck Breast Meat by Adenosine 5'-Monophosphate (AMP) using Response Surface Methodology

This study aimed to characterize and optimize the tenderization condition of duck breast meat by adenosine 5'-monophosphate (AMP), with the aid of response surface methodology (RSM). The results showed that the optimal conditions for the tenderization of duck breast meat were at the NaCl concentration of 3.99 g/100 g, AMP concentration of 13.83 mmol/L, temperature of 15.32°C, and marinating time of 8 h. Compared with control duck breast meat, AMP combined with NaCl treatment demonstrated significant effects on improvement of meat tenderness and decrease of cooking loss. Such effects might be ascribed to the combination of a series of biochemical reactions, e.g. increase of muscle pH, dissociation of actomyosin and inhibition of meat shrinkage. Therefore, the mixture of AMP and NaCl could be regarded as an effective tenderization agent for duck breast meat.

Application and optimization of the tenderization of pig Longissimus dorsi muscle by adenosine 5'-monophosphate (AMP) using the response surface methodology

Based on single factor experiments, NaCl concentration, adenosine 5'-monophosphate (AMP) concentration and temperature were selected as independent variables for a three-level Box-Behnken experimental design, and the shear force and cooking loss were response values for regression analysis. According to the statistical models, it showed that all independent variables had significant effects on shear force and cooking loss, and optimal values were at the NaCl concentration of 4.15%, AMP concentration of 22.27 mmol/L and temperature of 16.70°C, which was determined with three-dimensional response surface diagrams and contour plots. Under this condition, the observed shear force and cooking loss were 0.625 kg and 8.07%, respectively, exhibiting a good agreement with their predicted values, showing the good applicability and feasibility of response surface methodology (RSM) for improving pork tenderness. Compared with control pig muscles, AMP combined with NaCl treatment demonstrated significant effects on improvement of meat tenderness and reduction of cooking loss. Therefore, AMP could be regarded as an effective tenderization agent for pork.

Hyperspectral deep ultraviolet autofluorescence of muscle fibers is affected by postmortem changes

After slaughter, muscle cells undergo biochemical and physicochemical changes that may affect their autofluorescence characteristics. The autofluorescent response of different rat extensor digitorum longus (EDL) and soleus muscle fiber types was investigated by deep ultraviolet (UV) synchrotron microspectroscopy immediately after animal sacrifice and after 24 h of storage in a moist chamber at 20 °C. The glycogen content decreased from 23 to 18 μmol/g of fresh muscle in 24 h postmortem. Following a 275 nm excitation wavelength, the spectral muscle fiber autofluorescence response showed discrimination depending upon postmortem time (t0 versus t24 h) on both muscles at 346 and 302 nm and, to a lesser extent, at 408 and 325 nm. Taken individually, all fiber types were discriminated but with variable accuracy, with type IIA showing better separation of t0/t24 h than other fiber types. These results suggest the usefulness of the autofluorescent response of muscle cells for rapid meat-aging characterization.

Effects of Short-term Feeding Magnesium before Slaughter on Blood Metabolites and Postmortem Muscle Traits of Halothane-carrier Pigs

Fifty-four, mixed-sex, halothane-carrier crossbred (Yorkshire×Landrace) pigs with an average initial BW of 108.2±0.8 kg were randomly allotted to one of three dietary treatments for 5 d before slaughter: i) a control corn-soybean meal finisher diet devoid of supplemental magnesium; ii) a diet supplemented with 1.5 g/kg of elemental Mg from magnesium acetate; and iii) a diet supplemented with 1.5 g/kg of elemental Mg from magnesium sulfate heptahydrate. Serum creatine kinase (CK), lactate and glucose were analyzed at slaughter. Muscles from longissimus (LM) were packaged and stored to simulate display storage for muscle lactate and glycogen determinations at 0, 1, 2, 3, and 4 d. Mg supplementation reduced (p<0.05) serum CK and lactate concentration, but had no effect (p>0.05) on serum glucose. Daily change of muscle lactate concentration linearly increased (p<0.01), while glucose concentration linearly decreased (p<0.05) as storage time increased in all treatments. However, dietary Mg acetate and Mg sulfate supplementation in pigs elevated (p<0.05) muscle glycogen and reduced (p<0.05) muscle lactate concentrations, especially during the first 2 d of display, compared with pigs fed the control diet. This study suggests that short-term feeding of magnesium acetate and magnesium sulfate to heterozygous carriers of the halothane gene has beneficial effects on stress response and pork quality by improving blood and muscle biochemical indexes.

Minimising pain in farm animals: the 3S approach - 'Suppress, Substitute, Soothe'

Recently, the French National Institute for Agricultural Research appointed an expert committee to review the issue of pain in food-producing farm animals. To minimise pain, the authors developed a '3S' approach accounting for 'Suppress, Substitute and Soothe' by analogy with the '3Rs' approach of 'Reduction, Refinement and Replacement' applied in the context of animal experimentation. Thus, when addressing the matter of pain, the following steps and solutions could be assessed, in the light of their feasibility (technical constraints, logistics and regulations), acceptability (societal and financial aspects) and availability. The first solution is to suppress any source of pain that brings no obvious advantage to the animals or the producers, as well as sources of pain for which potential benefits are largely exceeded by the negative effects. For instance, tail docking of cattle has recently been eliminated. Genetic selection on the basis of resistance criteria (as e.g. for lameness in cattle and poultry) or reduction of undesirable traits (e.g. boar taint in pigs) may also reduce painful conditions or procedures. The second solution is to substitute a technique causing pain by another less-painful method. For example, if dehorning cattle is unavoidable, it is preferable to perform it at a very young age, cauterising the horn bud. Animal management and constraint systems should be designed to reduce the risk for injury and bruising. Lastly, in situations where pain is known to be present, because of animal management procedures such as dehorning or castration, or because of pathology, for example lameness, systemic or local pharmacological treatments should be used to soothe pain. These treatments should take into account the duration of pain, which, in the case of some management procedures or diseases, may persist for longer periods. The administration of pain medication may require the intervention of veterinarians, but exemptions exist where breeders are allowed to use local anaesthesia (e.g. castration and dehorning in Switzerland). Extension of such exemptions, national or European legislation on pain management, or the introduction of animal welfare codes by retailers into their meat products may help further developments. In addition, veterinarians and farmers should be given the necessary tools and information to take into account animal pain in their management decisions.

Current research in meat color

This review surveyed recent literature focused on factors that affect myoglobin chemistry, meat color, pigment redox stability, and methodology used to evaluate these properties. The appearance of meat and meat products is a complex topic involving animal genetics, ante- and postmortem conditions, fundamental muscle chemistry, and many factors related to meat processing, packaging, distribution, storage, display, and final preparation for consumption. These factors vary globally, but the variables that affect basic pigment chemistry are reasonably consistent between countries. Essential for maximizing meat color life is an understanding of the combined effects of two fundamental muscle traits, oxygen consumption and metmyoglobin reduction. In the antemortem sector of research, meat color is being related to genomic quantitative loci, numerous pre-harvest nutritional regimens, and housing and harvest environment. Our knowledge of postmortem chilling and pH effects, atmospheres used for packaging, antimicrobial interventions, and quality and safety of cooked color are now more clearly defined. The etiology of bone discoloration is now available. New color measurement methodology, especially digital imaging techniques, and improved modifications to existing methodology are now available. Nevertheless, unanswered questions regarding meat color remain. Meat scientists should continue to develop novel ways of improving muscle color and color stability while also focusing on the basic principles of myoglobin chemistry.

Adenine nucleotide concentrations and glycolytic enzyme activities in longissimus muscle samples of different pig genotypes collected before and after slaughter

Longissimus muscle samples from the pig genotypes Duroc (Du), Pietrain (MHS homozygote negative (PiNN), positive (PiPP)) and a Duroc-Pietrain crossbreed (DuPi) were analyzed. The PiPP samples showed a faster pH drop and higher electrical conductivity, drip loss and lightness values. Before slaughter the concentrations of the adenine nucleotides were comparable between the genotypes, but 40 min after slaughter (p.m.) the ATP concentrations decreased and IMP increased, to a higher extent in the PiPP pigs. The nucleotide values of the 12 h p.m. samples were again comparable. Activities of glycogen phosporylase (GP), phosphofructokinase (PFK) and lactate dehydrogenase (LDH) were nearly similar before slaughter. Forty minutes after slaughter the LDH activities increased in all pigs and the PFK activities in all genotypes but not in the PiPP. GP results were rather inconsistent indicating an earlier activation of this enzyme. The study showed that the reduced meat quality in the PiPP pigs is accompanied with rapid ATP degradation and accelerated enzyme activation.

The effect of transportation on the expression of heat shock proteins and meat quality of M. longissimus dorsi in pigs

This study investigates the effect of different transport times on meat quality and the correlation between meat quality and Hsp expression in M. longissimus dorsi (LD) of pigs. After transportation for 1h, 2h or 4h, respectively, blood plasma creatine kinase (CK) and lactate dehydrogenase (LDH) increased. The LD meat from 1h and 2h transported pigs had lower initial and ultimate pH values (pHi and pHu, respectively), higher drip loss and L(∗) values compared to controls, indicating a higher likelihood of pale, soft and exudative (PSE) meat. Meat quality was lower after 2h compared to 1h or 4h of transport. All four Hsps tested (alpha-B-crystalline, Hsp27, Hsp70 and Hsp90) by ELISA in the LD tissue of pigs tended to decrease after transportation. One possible mechanism resulting in poor meat quality in the LD after transport seems to be a decline in Hsp expression.

Differences in pig muscle proteome according to HAL genotype: implications for meat quality defects

Bidimensional electrophoresis was used to compare sarcoplasmic protein profiles of early post-mortem pig semimembranosus muscles, sampled from pigs of different HAL genotypes (RYR1 mutation 1841T/C): 6 NN, 6 Nn, 6 nn. ANOVA showed that 55 (18%) of the total of 300 matched protein spots were influenced by genotype, and hierarchical clustering analysis identified 31 (10% of the matched proteins) additional proteins coregulated with these proteins. Fold-changes of differentially expressed proteins were between 1.3 and 21.8. Peptide mass fingerprinting identification of 78 of these 86 proteins indicates that faster pH decline of nn pigs was not explained by higher abundance of glycolytic enzymes. Results indicate further that nn muscles contained fewer proteins of the oxidative metabolic pathway, fewer antioxidants, and more protein fragments. Lower abundance of small heat shock proteins and myofibrillar proteins in nn muscles may at least partly be explained by the effect of pH on their extractability. Possible consequences of lower levels of antioxidants and repair capacities, increased protein fragmentation, and lower extractability of certain proteins in nn muscles on meat quality are discussed.

The halothane gene, energy metabolism, adenosine monophosphate-activated protein kinase, and glycolysis in postmortem pig longissimus dorsi muscle1

The presence of the halothane gene results in PSE meat. However, the exact mechanisms linking the halothane gene and the incidence of PSE meat remain unclear. We hypothesize that the presence of the halothane gene accelerates energy consumption in postmortem muscle, which activates adenosine monophosphate-activated protein kinase (AMPK), leading to enhanced glycolysis and PSE meat. To test our hypothesis, energy status, AMPK activity, and glycolysis in the postmortem LM of the halothane gene carrier and halothane-negative pigs were compared. The results showed that the presence of the halothane gene accelerated energy depletion in postmortem muscle immediately after exsanguination, leading to rapid and early depletion of ATP, as shown by an increase in the (adenosine monophosphate + inosine monophosphate):ATP ratio in postmortem LM. In addition, an early AMPK activation was observed in LM from halothane carriers. The fructose-2,6-diphosphate concentration in postmortem LM was well correlated with AMPK activation. To be a potent stimulator of phosphofructose kinase, the increase in fructose-2,6-diphosphate is expected to activate phosphofructose kinase, a key enzyme controlling glycolysis, leading to enhanced glycolysis and early accumulation of lactic acid. In summary, this study showed that the presence of the halothane gene induced early energy depletion, which could be a primary reason causing AMPK activation, leading to accelerated glycolysis and an increased incidence of PSE meat. However, AMPK might also be activated by other mechanisms besides energy depletion, which warrants further studies.

Effects of available dietary carbohydrate and preslaughter treatment on glycolytic potential, protein degradation, and quality traits of pig muscles

The current study was conducted to determine the interactive effects of a glycogen-reducing diet fed to finishing pigs and length of preslaughter transportion on muscle metabolic traits, proteolysis of intermediate filament and costameric proteins, and meat quality traits. Large White gilts and barrows (n = 48) were selected at 88 kg of BW and individually fed for 21 d a diet (2.6 kg/d) either high (HC) or low (LC) in available carbohydrates. Six gilts and 6 barrows fed the HC and LC diets were subjected to 0 or 3 h of transportation on the day of slaughter. Muscle temperature and pH were measured at 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, and 24 h postmortem in the LM and 24 h postmortem in the dark (STD) and light (STL) portion of the semitendinosus. At 24 h postmortem, glycolytic potential (GP) was determined in the LM, STD, and STL, as well as proteolysis of titin, nebulin, desmin, vinculin, and talin in the LM and STD. The GP was lower (P < 0.05) in muscles from LC-pigs than in muscles from HC-pigs. The LC diet also resulted in lower (P < 0.05) pH, and a darker (P = 0.03), less (P < 0.01) yellow color in the STL. The LC diet decreased (P = 0.04) cooking losses in the STL and STD. The 3-h journey further decreased (P = 0.05) the GP in the STD, regardless of the diet, but transport had no effect (P > or = 0.67) on the GP of the LM and STL. Ultimate pH of the LM was lower (P = 0.02), and both portions of the semitendinosus were darker (P = 0.01) and less yellow (P < 0.01), in pigs transported 3 vs. 0 h. In pigs transported for 3 h, intact vinculin tended to be more (P = 0.08) degraded in the LM, which coincided with lower (P = 0.04) drip losses in the LM of pigs transported for 3 compared with 0 h. Increased (P < 0.01) proteolysis of titin paralleled lower (P = 0.02) shear force values in the STD of pigs transported 3 vs. 0 h. Although the present results demonstrated the potential of a glycogen-reducing diet to alter the GP of different porcine muscles, the effect of these changes on meat quality traits was limited to higher ultimate pH and darker color in the STL. The positive effects of length of transportation on water-holding capacity (LM and STD) and meat color (STD and STL) were only partially related to the resting muscle glycogen concentration because the 3-h transport lowered the GP only in the muscle with the lowest basal glycogen concentration.

Effect of dietary α-lipoic acid on growth, body composition, muscle pH, and AMP-activated protein kinase phosphorylation in mice1

The effects of alpha-lipoic acid (ALA) on the growth, body composition, postmortem AMP-activated protein kinase (AMPK) activation, and 24-h muscle pH were investigated. Thirty male C57BL/6J mice were fed diets containing 0, 0.5, or 1.0% ALA (DM basis). At the end of the 3-wk feeding trial, carcass weights decreased (P < 0.05) 14 and 30% for mice fed 0.5 and 1.0% ALA, respectively, compared with the 0% group, with decreases in BW as the levels of dietary ALA increased. This change in carcass weight occurred because carcass fat content for mice receiving 0.5 and 1.0% ALA was 7.32 and 8.09% lower (P < 0.05), respectively, than for the 0% ALA treatment, and because gonadal fat decreased (P < 0.05) 85% in mice fed 1.0% ALA compared with those fed 0% ALA. Dietary ALA caused a slight increase (P < 0.05) in carcass moisture content, with no (P = 0.07) effect on protein and ash content. Furthermore, ALA supplement decreased (P < 0.05) ADFI (DM basis) from 4.3 g/d for 0% ALA-fed mice to 3.4 g/d for 1.0% ALA-fed mice. At 20 min postmortem, pH was greater (P < 0.05) in muscle of mice fed 1.0% ALA than in muscle of mice fed 0% ALA. Ultimate (24-h) pH values differed (P < 0.05) among treatments, and mean values were 5.83, 6.08, and 6.29 for 0, 0.5, and 1.0% ALA, respectively. Phosphorylation of AMPK alpha subunit at Thr172, an indicator of AMPK activation, was decreased (P < 0.05) in muscle of ALA-treated mice at 20 min postmortem. Because AMPK has a crucial role in the control of glycolysis, the reduction in AMPK activation decreases glycolysis, and thereby increases the ultimate pH of postmortem muscle. In summary, dietary ALA supplement can decrease fat accumulation in mice, and because ALA increased muscle pH at 20 min and 24 h postmortem, these results suggest that dietary ALA supplementation might decrease carcass fatness and prevent the development of PSE pork and poultry. However, further research is required to test the effects of ALA in swine and poultry.

Effect of feed withdrawal and handling intensity on longissimus muscle glycolytic potential and blood measurements in slaughter weight pigs1

This study was carried out to evaluate the effect of feed withdrawal and handling intensity on blood acid-base responses and muscle glycolytic potential in slaughter-weight pigs. Sixty crossbred pigs (BW = 107.7 +/- 0.56 kg; 44 barrows and 16 gilts) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments: 1) feed withdrawal (0 vs. 24 h), and 2) handling intensity (low vs. high). The high-intensity handling treatment consisted of moving the pigs through a passage (12.2 m long x 0.91 m wide) for eight laps using an electric goad two times per lap. Pigs in the low-intensity handling treatment were moved at their own pace through the passage for eight laps using a livestock panel and paddle. Biopsy samples were collected from the LM at the beginning of feed withdrawal, at the end of the handling procedure, and 4 h after handling. Blood samples were collected 2 h before and immediately after the handling procedure. There were no interactions between feed withdrawal and handling intensity for any of the variables measured. Feed withdrawal decreased (P < 0.05) baseline and posthandling body temperature (38.85 vs. 38.65 degrees C; SEM = 0.060 and 39.70 vs. 39.37 degrees C; SEM = 0.04, respectively) and blood glucose, lowered (P < 0.05) baseline partial pressure of oxygen and partial pressure of carbon dioxide, and increased (P < 0.01) baseline and posthandling plasma free fatty acid concentrations. High-intensity handling produced higher (P < 0.01) posthandling lactate and glucose, and lower (P < 0.01) posthandling blood pH (7.33 vs. 7.18 +/- 0.02, respectively), bicarbonate, base excess, and total carbon dioxide than low-intensity handling. Longissimus muscle glycolytic potential of fasted pigs was lower (P < 0.01) than in fed pigs at the end of the handling procedure (177.2 vs. 137.0 micromol/g of wet tissue; SEM = 10.08, respectively). There was no effect of handling intensity on longissimus muscle glycolytic potential. Feed withdrawal did not attenuate the blood acid-base changes caused by handling; however, the combination of feed withdrawal and handling decreased muscle glycolytic potential.