Adrenal ascorbic acid depletion as an index of preslaughter stress in pigs

The weight of the adrenal glands and the amount of ascorbic acid they contained were measured in Large White pigs subjected to various preslaughter treatments. Compared with transport for four hours preslaughter, one hour's transport resulted in adrenal glands which weighed less and which contained less ascorbic acid. Pigs mixed with strange pigs in lairage had heavier adrenals containing more ascorbic acid than those of unmixed pigs. Increasing lairage time up to twenty-four hours raised both the concentration and total amounts of ascorbic acid in the adrenal glands. The results suggest that the depletion of ascorbic acid from the adrenal glands can be used as a measure of the stress experienced by animals during the preslaughter period and the extent to which resting in lairage allows them to recover.     

Potential interactions between the effects of preslaughter stress and post-mortem electrical stimulation of the carcasses on meat quality in pigs

The experiment examined the influence on pork quality of the electrical stimulation of carcasses from pigs subjected to different ante-mortem handling treatments. The carcasses were subjected to a slow chilling regimen to reflect less than ideal commercial practice. A total of 288 pigs (mean live weight 89 kg) of both sexes and a range of genotypes were used. They came from the Meat and Livestock Commission 's Pig Development Unit at Stotfold and were processed in 12 equal batches. Prior to slaughter they were transported for 2 h (80 km) at a stocking density of 0.5 m(2)/100 kg live weight. Preslaughter handling included being mixed or not with unfamiliar animals and being given a 3 h rest in lairage or not. One group received handling to simulate that in stunning races immediately before slaughter. There were no material interactions between the effects of ante- and post-mortem handling. Pigs rested 3 h in lairage had lower plasma cortisol levels irrespective of whether mixed with unfamiliar animals. Plasma lactate concentrations increased with greater ante-mortem stress. Pigs subjected to the simulated stunning race treatment had elevated carcass temperature. Greater ante-mortem stress progressively elevated pHu in the muscles and tended to reduce eating quality. Electrical stimulation followed by slow chilling raised initial muscle temperature, reduced pH(45) and pHu, and produced meat that was paler, had higher hue and saturation values and lost more drip during storage. Neither instrumentally-determined texture nor taste panel texture was affected, but electrical stimulation decreased juiciness and increased pork flavour. Overall eating quality was not affected by stimulation.     

Meat quality traits of commercial hybrid pigs in Argentina

This report describes the meat quality of two INTA hybrids (hybrid females) sired by Duroc (D) or Yorkshire (Y) boars and a third one from PIC (S), a cross of females C22 to 412 boars. Starting at 30 kg live weight, 18 barrows and 18 gilts of each genotype were kept in identical conditions until slaughtered at 110 kg. Longissimus dorsi muscles were analyzed. Means differed significantly (P < 0.05) for drip loss (higher in S); tenderness (more tender in D), water holding capacity (higher in Y); cooking loss (higher in Y); colour parameter L^∗ (lower in D) and b^∗ (higher in S) and intramuscular fat content (higher in D). As a result of sensory analysis, it was found that D was the most tender and juicy. There were few sex effects and no genotype–sex interactions. Distinct differences in meat quality between hybrids do exist, with D superior, S the worst, and Y intermediate.     

Meat quality characteristics in different lines of Iberian pigs

Physico-chemical parameters involved in technological meat quality for dry cured processing of four different lines (Entrepelado, Lampi?o, Retinto and Torbiscal) of Iberian pigs were studied in the Masseter (MS) and Longissimus dorsi (LD) muscles. The line of Iberian pig significantly affected intramuscular fat content of MS muscle, animals from the Torbiscal line showing lower values. Proportions of several fatty acids of total lipids and polar lipids from the MS muscle were also affected. However, fatty acid composition and total lipids, neutral lipids and polar lipids of LD muscle and neutral lipids of MS muscle were scarcely affected. Lipid oxidation was also unaffected by Iberian pig line, but instrumental colour parameters of MS muscle showed significant variations.     

Meat quality and fatty acid profile of Brazilian goats subjected to different nutritional treatments

This study evaluated the effect of feed restriction and goat genotype on meat quality. Three genotypes (Brazilian native breed Canindé; Brazilian native breed Moxotó; and F1 Boer crossbred animals obtained by crossing Boer bucks with local breed does) and three different feeding regimens (ad libitum fed, AL; restricted fed at 75% of the ad libitum, R.75; or restricted fed at 50% of the average ad libitum intake, R.50) were used. There was no difference (P > 0.05) in chemical composition, total and soluble collagen, and shear force of the Longissimus lumborum muscle among genotypes. However, AL had greater amounts of soluble collagen and crude protein in the muscle (P < 0.05) than R.75. No difference (P > 0.05) was observed for the myofibrillar fragmentation index. The goat genotype presented few differences in their fatty acid profiles. However, goats fed ad libitum had a more favorable fatty acid profile for human health with greater concentrations of oleic acid, unsaturated fatty acids, and conjugated linoleic acid.     

Meat quality: Influence of fatness of pigs on the eating quality of pork

The eating qualities of pork from the longissimus dorsi muscles of pigs showing a wide variation in fatness (10-40 mm, back fat thickness) were assessed by taste panel after either the excised muscle had been grilled or a complete loin joint had been roasted. The average panel scores for texture and juiciness covered a wide range but were not consistently related to fatness. Although meat from fatter pigs tended to be judged more tender in direct comparisons, overall the results did not support the contention that fatness in the carcass is associated with tenderness in the lean meat.     

牲畜的宰前运输对肉品品质的影响

大量研究结果表明,不合理的运输方式和运输时间会引起牲畜体内水分流失,从而引起体重下降;宰前运输产生的强烈应激会导致牲畜糖原损失,产生高的极限pH,进而极大地影响肉品品质.本文综述了运输过程中牲畜体重下降、糖原损失的研究情况,对可能出现的影响肉品品质的问题做了具体的阐述,对其机理进行了简单的介绍,并提出了一定的解决措施.以期为国内的相关研究及生产实际提供一些参考.     

Muscle metabolic traits, post mortem-pH-decline and meat quality in pigs subjected to regular physical training and spontaneous activity

Ninety-six female and male pigs were assigned to one of three treatments, 'confined' (C),'trained'(T) or 'free' (F) allowing for different levels of physical activity during the growth interval from 30 to 100kg. Treatment C consisted of individual housing in pens of 2.5 m(2); treatment T of individual housing and regular treadmill training and treatment F of housing in pens of 36 m(2) (40 pigs/pen). In m. biceps femoris (BF), the activity of lactate dehydrogenase (LDH) was decreased between 9 and 12% by training (treatment T vs C). Likewise, in BF from female pigs, training increased the activity of citrate synthase (CS) and of 3-OH-acyl-CoA-dehydrogenase (HAD) by 18 and 21%, respectively. Spontaneous activity (treatment F) reduced the activity of LDH for five muscles between 10 and 16% when compared with treatment C. Around the time of slaughter, glycogenolysis of BF was less for treatment F (6-17%) than for C and T (33-38%). Moreover, in BF from female pigs in treatment F, the initial but not the ultimate pH was increased when compared with treatment C. In comparison to C and T, treatment F improved juiciness in BF from male pigs and increased the amount of salt soluble protein in m. longissimus dorsi.     

Meat quality of tenderloin from Iberian pigs as affected by breed strain and crossbreeding

In 2007, a new National Quality Standard was published in Spain to regulate the products derived from the Iberian pig carcass, including for the first time fresh meat. In the same way, four different Iberian strains were recognized as official (Lampiño, Entrepelado, Retinto and Torbiscal). A batch (n = 10) of each pig strain was selected using neutral DNA markers, and another batch of the most common crossbreeding pigs (Iberian × Duroc) was included into the study as a control. The main meat quality parameters of tenderloin, the most expensive meat cut for fresh consumption, from those five pig groups were analysed. Retinto and Lampiño strains showed the closest phenotypic distances, followed by Entrepelado strain. Meat from crossed and Torbiscal pigs had lower water holding capacity, L∗ and a∗, and higher SFA than meat from the other three strains. Crossbred pigs had the lowest protein, intramuscular fat and PUFA contents.     

Meat quality assessed Ante- and Post mortem by different ryanodine receptor gene status of pigs

Different breeds and crossbreeds (total 63) of pigs with defined genotype (DNA based test on RYR 1 gene status) were divided in normal (non mutant), heterozygotes (carriers, monomutant) and homozygote positive (dimutant) animals. Muscle biopsy samples were taken at approximately 80 kg live weight using an efficient non-stress spring-loaded biopsy instrument. After incubation of muscle samples (39 °C, 1 hr) analyses pH, WHC (fluid), R value (ITP:ATP) were performed. After slaughter, meat quality values (pH₁, pH₂₄, R value, colour, drip loss) were also carried out. Heterozygotes were intermediate and between both homozygote pig groups in most meat quality values analysed. Using WHC (fluid volume) values (0.45 and 0.48 respectively) it was possible to divide heterozygotes into two groups, each closer to homozygotes. The values of pH, WHC (fluid), as measured at definite times on the biopsies, were correlated with the pH₁ post-mortem value (r approx 0.6–0.7). The results support previous findings on the possibility of differentiating pigs within DNA test-defined groups. Introducing the gene into a pig population could be useful, in improving leanness and muscling: but meat quality is certain to deteriorate. Further experiments are needed to support the possibility of identifying PSE-prone pigs from among normal non mutant pigs.     

Meat quality comparison of Berkshire, Duroc and crossbred pigs sired by Berkshire and Duroc

The object of this study is to specify features determining meat quality of Berkshire and Duroc and influence of these purebreds on meat quality of crossbred pigs. In total, 37 purebred pigs (Berkshire and Duroc: originating from line breeding in Kagoshima Prefecture and Miyagi Prefecture, respectively) and two crossbreeds (LDB and LDD: produced by crossing Berkshire and Duroc boars to Duroc-Landrace sows) were used. Berkshire accumulated more subcutaneous and abdominal fat and had small loin eye muscle area, but accumulated less intramuscular fat than Duroc. There were no differences in meat colour and tenderness between the two purebreds. But Berkshire was less than Duroc in drip loss. As for fatty acid of inner and outer subcutaneous fat, Berkshire contained significantly higher concentration of saturated fatty acids, but had lower concentration of unsaturated fatty acid than Duroc. As a result, the melting point of inner and outer subcutaneous fat and perirenal fat of Berkshire was significantly higher than that of Duroc. Furthermore, though there was no breed difference in concentration of saturated fatty acids of intramuscular fat, Duroc had more oleic acid (C18:1) than Berkshire. Fatty acid concentrations of inner and outer subcutaneous fat and intramuscular fat as well as melting points of both subcutaneous fat layers and perirenal fat were the same in Berkshire and LDB and in Duroc and LDD. These results suggest that there were remarkable differences between Berkshire and Duroc in fat quality traits; also, both breeds as terminal sires influenced crossbred pigs' fat accumulation and fat quality traits.     

Meat quality is associated with muscle metabolic status but not contractile myofiber type composition in premature pigs

Longissimus muscles were sampled from Erhualian (EHL) and Pietrain (PIE) pigs at 20kg of body weight. No breed differences were detected in either the proportions or the mRNA/protein expression of respective MyHC isoforms, or the mRNA expression of PGC-1α (all P>0.10). However, meat quality traits were already divergent between breeds, and were associated with distinct energy metabolic status, as reflected by dramatically lower AMPK activity yet higher CK and LDH activities (all P<0.01) in longissimus muscle of EHL pigs. Moreover, mRNA expression of glucocorticoid receptor (GR) was found to be higher (P<0.05) in longissimus muscle of EHL pigs. These results indicate that the differences in meat quality traits occur early in premature pigs, and these are attributed to skeletal muscle energy metabolism and not contractile myofiber type composition. Breed-specific GR expression in muscle may be related to the pattern of energy metabolism and meat quality, yet the mechanism awaits further investigation.     

Plasma and muscle cortisol measurements as indicators of meat quality and stress in pigs

Post-slaughter blood samples and muscle samples were collected from pigs slaughtered at the completion of a live-animal performance trial. There were two lines of pigs in which the halothane allele (n) was segregating. The lines were a lean line selected for rapid lean growth and an unselected fat line. There were homozygous normal (NN), homozygous halothane positive (nn) and heterozygous (Nn) genotypes in both lnes. Cortisol was measured in the plasma of the blood samples and in muscle juice obtained by high-speed centrifugation. Meat quality was assessed using pH, colour, fibre-optic probe, drip loss and cure yield measurements. Plasma cortisol concentrations in the fat line were significantly (P < 0·05) greater than thosein the lean line but concentrations did not differ significantly for the three halothane genotypes. Carcasses classified as dark, firm and dry (DFD) had significantly (P < 0·05) greater muscle cortisol concentrations than those classified as normal. Plasma and muscle cortisol concentrations of carcases classified as pale, soft and exudative (PSE) did not differ significantly from those classified as normal. Correlations between muscle cortisol and meat quality attributes were generally highly significant (r = 0·31 to r = 0·51, P < 0·001) There was a highly significant correlation (r = 0·73, P < 0·0001) between plasma and muscle cortisol concentrations.     

Effect of preslaughter handling on muscle glycogen level and selected meat quality traits in beef

The ante-mortem and post-mortem glycogen levels in bull muscle were studied to determine their influence on the ultimate pH, cooking loss and shear force. Forty-three bulls (13 Holstein, 12 crosses Holstein × Belgium blue, 9 Slovak Pied and 9 crosses Slovak Pinzgauer × Piemontese) were tied, housed and divided in control (A, n = 30) and stressed (B, n = 13) groups before slaughter. At the institute abattoir, the group B animals were mixed and kept overnight. In group A, bulls were slaughtered immediately after arrival at the abattoir. The following values of muscle were determined: (1) glycogen ante mortem from m. semitendinosus (ST) (biopsy technique, Biotech Nitra), (2) glycogen post mortem (1 hr, 3 hr, 48 hr) from longissimus dorsi muscle (LD), (3) ultimate pH, cooking loss and shear force 48 h post mortem. The results show that the glycogen concentrations ante mortem (ST) and 1 hr post mortem (LD) from unstressed animals were similar (p > 0.05). The ante-mortem and post-mortem (1 hr, 3 hr) muscle glycogen concentration were depleted (p < 0.01) in all stressed bulls. Differences between stressed and unstressed animals (p < 0.01) were found in ultimate pH, cooking loss and in shear force (p < 0.05). Significant correlations (p < 0.01) between ante-mortem (ST) and postmortem (LD, 1 hr, 3 hr) muscle glycogen and ultimate pH and cooking loss supported the possibility of using an efficient biopsy technique in combination with a simple method of glycogen estimation (iodide method) to predict metabolic exhaustion (glycogen depletion) and/or dark cutting condition of bulls.     

Influence of food withdrawal at various times preslaughter on carcass yield and meat quality in sheep

Castrated male crossbred lambs were fed a complete pelleted diet ad libitum for 4 weeks prior to slaughter at a liveweight of about 32 kg. Forty lambs were killed directly off feed and forty each after 24, 48 and 72 h from food withdrawal. They had access to water at all times. Fasting had a significant effect on the weights of all body components examined except the combined fleece and feet. Liveweight was lost slightly more rapidly over the initial 24 h after food withdrawal, and this was attributable mainly to a 20% decrease in the weight of the gut contents. The overall rate of liveweight loss between 0 and 72 h was 0.14% h^?1. The corresponding loss of carcass weight was 0.085% h^?1, some reduction in yield being evident by 24 h of fast although a significant effect was seen only after 48 h. Liver weight was lost most rapidly (0.69% h^?1) over the initial 24 h but continued to be lost throughout fasting. Associated with the initial decrease in liver weight was a rapid loss of glycogen to very low levels by 24 h after food withdrawal. Fasting also reduced muscle glycogen concentrations but had no large or consistent effects on ultimate pH, reflectance or water-holding capacity.     

Microbial stress response in minimal processing.

"Bacteria have evolved adaptive networks to face the challenges of changing environments and to survive under conditions of stress. Therefore, the efficiencies of inactivation and preservation methods need to be assessed, especially with regard to the enormous potential of food pathogens to adapt to a wide variety of stress conditions. All adaptive responses, whether to changing nutrients or to various stresses encountered in minimal processing, involve a series of genetic switches that control the metabolic changes taking place. A common regulatory mechanism involves the modification of sigma (sigma) factors whose primary role is to bind to core RNA polymerase conferring promoter specificity directing expression of specialty regulons involved in heat-shock response, the chemotactic response, sporulation, and general stress response. Examples of the latter regulon in Gram-positive bacteria (the sigmaB regulon) and in Gram-negative bacteria (the RpoS regulon) will be discussed in more detail. Cellular adaptive mechanisms to starvation, cold shock, heat shock, (weak) acids, high osmolarity and high hydrostatic pressure will be described and their significance in food preservation and safety will be discussed."     

Relationships between subjective and objective assessments of stress at slaughter and meat quality in pigs

A study was carried out to relate subjective and objective measures of stress at slaughter and meat quality in pigs. Thirteen slaughter plants were visited. The systems used for handling the pigs pre-slaughter and the levels of stress experienced by the animals were subjectively assessed. The sound level immediately before stunning was also measured. Generally, systems that were rated as being most stressful also produced higher levels of sound, probably because of the vocalisations of the pigs. As the size of plant increased, there was a tendency for the level of stress, and the recorded sound level, to increase. This appeared to be because larger plants operated faster and were more likely to use restraining conveyors supplied by races to handle the animals before stunning. The restraint associated with these seems stressful to pigs. Five plants were selected for further study. Two had been assessed as having handling systems that produced a low level of stress in the pigs, one as having a system producing a medium level, and two as having poor systems producing high levels of stress. Blood samples were collected at exsanguination, and meat quality was assessed. As the level of subjectively assessed stress experienced by the pigs increased, so did the average blood levels of lactate and creatine phosphokinase (CPK). There was also a progressive increase in the potential incidence of pale, soft, exudative (PSE) and dark, firm, dry (DFD) meat in the plants using more stressful handling systems. Additionally, there were positive relationships between sound level and lactate and CPK, and sound level and indices of poorer meat quality. Cortisol concentrations were not different in pigs killed in the different systems and probably reflect events earlier in the handling process, such as in transport and lairage, rather than the stress experienced immediately before stunning. The overall conclusion was that subjective assessments of the stress suffered by pigs correlate well with objective measures and that higher stress levels are associated with poorer meat quality.     

Meat quality assessment using biophysical methods related to meat structure

This paper overviews the biophysical methods developed to gain access to meat structure information. The meat industry needs reliable meat quality information throughout the production process in order to guarantee high-quality meat products for consumers. Fast and non-invasive sensors will shortly be deployed, based on the development of biophysical methods for assessing meat structure. Reliable meat quality information (tenderness, flavour, juiciness, colour) can be provided by a number of different meat structure assessment either by means of mechanical (i.e., Warner-Bratzler shear force), optical (colour measurements, fluorescence) electrical probing or using ultrasonic measurements, electromagnetic waves, NMR, NIR, and so on. These measurements are often used to construct meat structure images that are fusioned and then processed via multi-image analysis, which needs appropriate processing methods. Quality traits related to mechanical properties are often better assessed by methods that take into account the natural anisotropy of meat due to its relatively linear myofibrillar structure. Biophysical methods of assessment can either measure meat component properties directly, or calculate them indirectly by using obvious correlations between one or several biophysical measurements and meat component properties. Taking these calculations and modelling the main relevant biophysical properties involved can help to improve our understanding of meat properties and thus of eating quality.