宰前运输、休息、禁食和致晕方式对鲜肉品质影响的研究进展

屠宰前畜禽在经历装卸、运输与休息、入栏、禁食以及宰前致晕等过程中,要面临许多应激原的刺激,如饥饿、颠簸、拥挤等客观因素,以及由此导致的惊恐、紧张等心理因素。宰前处理程序带来的应激大部分对肉质的形成是不利的,但是运输前的禁食、供水以及宰前休息等可能对肉质有一定的改善作用。电击晕、CO2致晕,二者都是机械化屠宰经常采用的工序,国内对于CO2致晕的应用与研究均较少。本文综述了近年来国内外有关宰前运输、休息、禁食及致晕方式对鲜肉品质影响的最新研究成果,旨在为优质肉的生产及相关科学研究提供参考。     

Effects of combined premortal and postmortal electrical treatment on the quality of meat

Just as postmortal electrical stimulation of rapidly cooled bovine carcass halves generally has positive effects on the quality of meat (pH, meat consistency, water-binding capacity), the same applies to premortal electrical treatment of animals (electrical stunning) or the combined pre- and postmortal electrical treatment. Exemplified for selected muscles of more than 100 heads of cattle of different slaughter class and slaughter category it was demonstrated, however, that combined electrical treatment of bulls is liable to entail a higher percentage of lower-quality DFD-meat. The results of the experimental studies of electrical treatment and quality analysis are presented together with a discussion of potential sources of quality reduction in the case of bull meat.     

电击晕处理对肉鸽屠宰应激及宰后鸽肉品质的影响

为探究电击晕处理对肉鸽屠宰应激和宰后鸽肉品质的影响，本实验选取相同饲养条件下日龄为28 d的肉鸽，以击晕电压0 V为对照组，通过测定血液生化指标和肌肉理化指标，分析不同击晕电压(50～90 V)对肉鸽应激反应和宰后胴体品质的变化。结果表明：电击晕处理组肉鸽屠宰后血液中肌酸激酶(creatine kinase,CK)、促肾上腺皮质激素(adrenocorticotropic hormone,ACTH)和乳酸脱氢酶(lactate dehydrogenase,LDH)水平与对照组相比整体上均有一定程度的下降，在击晕电压60 V时总体达到最低水平；血液中皮质酮激素质量浓度随着击晕电压(0～90 V)的增大先降低后增加，在电压超过70 V时高于对照组，说明70 V以上的电击晕处理会增加肉鸽的屠宰应激水平；电击晕处理对宰后鸽胸肉的pH值影响不显著，与对照组相比，宰后24 h鸽胸肉亮度(L^*值)略有降低而红度(a^*值)增大，60～70 V电压处理组鸽肉的滴水损失率、蒸煮损失率及剪切力均保持在较低水平，此时鸽肉的保水性和嫩度相对较好。综上，60～70 V的...     

Effects of the stunning procedure and the halothane genotype on meat quality and incidence of haemorrhages in pigs

A total of 313 pigs (127 halothane-free, NN, and 186 heterozygous halothane, Nn) were slaughtered in four batches at two commercial abattoirs with two different stunning systems, an automatically head-only followed by head-to-chest electrical stunner and a compact carbon dioxide (CO(2)) stunning unit. Meat quality on the loin muscle was assessed by measuring electrical conductivity (PQM) and colour (Minolta CR 200) at 7 h post mortem, and ultimate pH. Loins showing PQM >6.0 μs were classified as clearly pale, soft and exudative (PSE) meat. The incidence of petechiae, ecchymosis and haematomas in the shoulders, loins and hams was also evaluated. In the abattoir equipped with the electrical stunning system, a higher incidence of potentially PSE meat was found compared with the abattoir equipped with CO(2) stunning (35.6 vs. 4.5%). Likewise, electrical stunning increased significatively the incidence of petechiae in the loins, shoulders and hams, and ecchymosis in the loins and hams. Also, the incidence of PSE meat was higher in the Nn pigs compared with NN pigs (24.7 vs. 7.9%). It is suggested that for improving meat quality and reducing incidence of haemorrhages electrical stunning should be avoided. Further improvements in meat quality can be achieved by eliminating the halothane gene specially in CO(2)-stunned pigs.     

Effect of electrical stunning or sticking without stunning on the microstructure of zousoon, a Chinese semi-dry pork product

The microstructure of muscle fibers from pigs killed following electrical stunning was compared to that from pigs killed after tying-resting and sticking. Examination of the muscle fibers demonstrated that electrical stunning resulted in contracture bands that caused tearing and fragmentation of the myofibers/myofibrils. On the other hand, tying-resting and sticking was not accompanied by microstructural fragmentation of the muscle fibers. Results indicate that electrical stunning of hogs causes fragmentation and breakage of the muscle fibers so that the meat is not suitable for production of Zousoon-a semi-dry shredded Chinese pork product and other similar items prepared from prerigor pig muscle. Heating and drying intensify the deteachment of the myofibrils from the muscle fiber bundles, which is caused mainly by electrical stunning or stimulation and improper conditioning following slaughter. The combined effects of electrical stunning and heating-drying appear to be responsible for the fragmentation of the muscle fibers/myofibrils and contribute to the unsuitability of prerigor muscle from electrically stunned pigs for use in the production of Zousoon. Since sticking of pigs without stunning does not meet humane slaughter standards, alternative animal welfare slaughter procedures should be examined from the standpoint of their usefulness in producing Zousoon.     

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.     

Recent concerns about stunning and slaughter

This review summarises information that is relevant to concerns that have recently been expressed about stunning and slaughter. It is known that captive bolt stunning can result in brain material passing to the lungs via the jugular veins. If future studies show that BSE prions pass beyond the lungs to the edible carcass, there will be a move away from captive bolt stunning in large cattle towards electrical stunning. Greater use of electrical stunning in large cattle will increase the importance of blood splash in the beef industry. The theoretical causes of blood splash are reviewed to improve our understanding of this problem. In some situations it can be due to excessive venous pressure causing rupture of a capillary bed some distance from the source of the pressure rise, but it is not known whether this applies to electrical stunning. Gas stunning is replacing electrical stunning for poultry because it can reduce blood spots, which is a similar condition to blood splash. Several gas stunning methods are now being used, but it is not clear which of these is the most humane. Anoxic stunning leads to carcass convulsions and this causes more carcass damage. In fish, recent developments in electrical stunning are showing promise in overcoming problems with carcass damage. It is recommended that rock lobsters should be chilled or frozen before butchery, to ensure a humane death.     

False aneurysms in carotid arteries of cattle and water buffalo during shechita and halal slaughter

It has previously been shown that the cattle brain is supplied with blood via a basi-occipital plexus, in addition to branches from the carotid and basilar arteries. In addition it has been shown during conventional stunning and slaughter that the carotid arteries in cattle can develop false aneurysms at their severed ends and this can curtail exsanguination. This investigation examined whether false aneurysms can occur during religious slaughter, and during bleeding following electrical stunning that simultaneously induced a cardiac arrest. The prevalence of large (>3 cm outer diameter) false aneurysms in cattle carotid arteries was 10% for both shechita and halal slaughter. The prevalence of animals with bilateral false aneurysms (at least 2 cm in one artery and at least 3 cm diameter in the opposite artery) was 7% and 8% for shechita and halal slaughter, respectively. No false aneurysms occurred during bleeding in cattle that were electrically stunned and simultaneously developed a cardiac arrest. The combination of false aneurysms and collateral routes to the brain present a risk of sustained consciousness during religious slaughter in cattle.     

A perspective on the electrical stunning of animals: are there lessons to be learned from human electro-convulsive therapy (ECT)?

Animals have been slaughtered by humans since time immemorial. Over the last few generations attention has been focused on minimizing the animal's pain and suffering during slaughter. Based on the assumption that loss of consciousness due to electrical stunning combined with exsanguination is a humane technique of slaughter, this procedure has become one of the most widely employed methods in commercial meat production, being used in almost all species. In recent years, some shortcomings with this method of minimizing the animal's suffering have been noted. Electrical stunning is probably more akin to human electro-convulsive therapy (ECT) than to epilepsy, and some of the negative aspects of unmodified ECT may be present during electrical stunning, further questioning the use of electrical stunning in the slaughter of animals.     

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.     

The effect of stunning method on the incidence of PSE meat and haemorrhages in pork carcasses

Two commercial pig abattoirs (A and B) equipped with a head-only and head-to-chest electrical stunning systems, and two (C and D) equipped with compact carbon dioxide (CO(2)) stunning systems, were visited during 3 days to evaluate the effects of the stunning system on meat quality and haemorrhages. Meat quality was evaluated by measuring muscle electrical conductivity (PQM) and colour (Minolta Chromameter) at 2 and 7 h post mortem (abattoirs A and C, and B and D, respectively). PQM and colour were measured in 2486 and 2321 loins respectively. Also ultimate pH (pHu) was measured in 2395 loins at 24 h post mortem. Haemorrhages were evaluated by recording the incidence of petechiae, ecchymosis and haematomas, bone fractures were also recorded. A total of 1980 shoulders, 3943 loins, and 5438 hams were inspected. In the abattoirs equipped with the electrical stunning systems, a higher (P<0.05) incidence of potentially PSE meat (PQM>6) was found compared with the abattoirs equipped with CO(2) stunning. Likewise, the loins from electrically stunned pigs were paler than those from CO(2) stunned pigs (P<0.05). Electrical stunning increased the incidence of petechiae in the loin and the ham (P<0.05). No shoulder, loin or ham with bone fractures was found in the abattoirs studied. Therefore, CO(2) stunning reduces the incidence of PSE meat and of petechiae on muscle fascia of loins and hams, compared with electrical stunning. However, petechiae are not of great importance because they can be removed from the affected commercial cuts.     

不同屠宰方式对蒙古羊应激及羊肉食用品质的影响

以内蒙古蒙古羊为研究对象,对比分析抹脖子屠宰、掏心式屠宰及电击晕屠宰对蒙古羊应激及羊肉食用品质的影响,利用生化分析仪等仪器对蒙古羊血液指标及食用品质进行测定。结果表明：经电击晕后屠宰,肉羊血液中乳酸含量、皮质醇含量、乳酸脱氢酶活性及肌酸激酶活性显著低于其他2 种方式,肉羊在屠宰过程中应激反应也最小;相比于抹脖子及掏心式屠宰2 组,电击晕组羊肉的蒸煮损失率较低,而嫩度高于抹脖子组,且与掏心组差异不显著,红度值（a*）高于上述2 组,且电击晕组羊肉的硫代巴比妥酸反应物值最低;营养方面,电击晕及掏心式屠宰可提高羊肉中不饱和脂肪酸的含量。因此,从肉羊屠宰食用品质及经济效益等方面比较,电击晕屠宰方式可以减小肉羊应激反应,提高肉羊屠宰企业的经济效益,符合动物福利屠宰要求。     

Effect of different carbon dioxide concentrations and exposure times in stunning of slaughter pigs: Impact on animal welfare and meat quality

The objective of this study was to determine the impact of different slaughter procedures on animal welfare and meat quality. Before slaughter in a dip-lift, one-gondola system, 460 pigs were exposed to an atmosphere containing either 80% or 90% CO(2) for 70 or 100s, and at the longer exposure time with stun-to-stick intervals of either 25-35 or 40-50s. Clinical parameters (reflexes, catecholamines and lactate) showed deficiencies in animal welfare after stunning with 80% CO(2) for 70 and 100s, with an interval of 40-50s, and with 90% CO(2) for 70s. Stunning with 80% CO(2) for 70 or 100s always induced stress, as indicated by higher lactate levels, and reduced meat quality as indicated by low pH(24) values (5.4 in Musculus longissimus and 5.5 in Musculus semimembranosus) and low impedance (Py(24)) values, especially in combination with the longer stun-to-stick interval (40-50s). Stunning with 80% or 90% CO(2) in a dip-lift system was found to be acceptable for animal welfare (percentage of clinical reflexes) only in combination with the longer exposure time of 100s and the shorter stun-to-stick times of 25-35s. When 90% CO(2) was used, the longer stun-to-stick interval of 40-50s also gave results acceptable with regard to animal welfare. Generally, in comparison to 80% CO(2) stunning meat quality was superior (higher pH(24) and Py(24) values) after stunning with 90% CO(2).     

The effect of stress, applied immediately before stunning, on pork quality

The effect on meat quality characteristics of stress, applied during a short period just before stunning, was studied on slaughterpigs (113 boars, 85 gilts). Sexes were kept separately and only pigs that had been stunned correctly were included. Aggressive behaviour during lairage occurred more frequently in boars (about twice) than in gilts. Just before stunning, two animals of the same sex, that were lairaged for an equal period at the slaughter facility, were moved as quietly as possible to the stunning pen, after which one pig was stunned immediately and the other subsequently forced to move through the stunning pen over a period of 1 min. Stress resulted in lower pH values and higher temperatures in the semimembranosus (SM) and the longissimus lumborum (LL) muscles and a higher rigor mortis value of the SM, at 45 min post mortem. Stress affected water holding capacity of the LL negatively at 24 h p.m. Statistically significant interactions were present for sex×stress for several meat quality traits. In general, gilts reacted more strongly to short periods of stress than did boars.     

Comparison of CO(2) stunning with manual electrical stunning (50 Hz) of pigs on carcass and meat quality

The effects of carbon dioxide stunning on carcass and pork quality attributes were compared with the effects of manual electrical stunning using either head-only or head-to-brisket electrodes. A total of 30 Large White×Landrace boars (homozygous dominant for the halothane gene) were randomly allocated immediately prior to slaughter to one of three stunning treatments: carbon dioxide (90% CO(2)), head only (HO; 1.3 A for 4 s at a frequency of 50 Hz) or head to brisket (HBR; 1.3 A for 4 s at a frequency of 50 Hz) electrical stunning. The pH of the M. longissimus thoracis (LT) muscle measured at two sites [between the fifth and sixth thoracic vertebrae (Site 1) and the last thoracic rib (Site 2)] at 40 min post-slaughter was lower (P<0.001) in HBR stunned pigs compared with both CO(2) and HO stunned pigs. No differences in ultimate pH of the LT at either measurement site were found due to stunning method. However, a faster (P<0.05) relative rate of pH decline was found in the LT at Site 1 from HBR stunned pigs compared with CO(2) stunned pigs. No difference in the relative rate of muscle pH decline (P>0.05) between stunning methods was found in the LT muscle at Site 2. Pork from HBR stunned pigs was paler (P<0.05) and had a higher (P<0.001) percentage drip loss compared with pork from HO and CO(2) stunned pigs. LT muscles from HBR stunned pigs had lower (P<0.001) WB shear force values compared with pork from HO stunned pigs (6.57 vs. 8.12 kg, S.E.D. 0.49). Carcass quality was improved by CO(2) stunning, with less (P<0.05) ecchymosis-affected pork trimmed from shoulder primals compared with electrically stunned pigs. These results indicate that manual electrical stunning of pigs using HO tongs and CO(2) stunning reduced percentage drip loss, reduced muscle lightness and reduced the rate of muscle pH decline compared with pigs manually electrically stunned using HBR tongs.     

Head current during and blood splashes after electrical stunning in relation to characteristics of the pig's body

In order to evaluate electrical stunning in relation to the incidence of blood splashes, meat quality and carcass quality parameters, 2035 pigs, heterozygous for the halothane gene, were observed during slaughter at a commercial slaughterhouse. The head current during electrical stunning is significantly higher (P<0.01) in gilts with a lower live weight (P<0.0001) or cold carcass weight (P<0.0001) and a higher lean meat percentage (P<0.0001). Also the incidence of blood splashes in the ham is significantly higher in gilts (P<0.0001) with a higher lean meat percentage (P=0.0028; odds ratio=1.11), a lower live weight (P=0.003; odds ratio=0.98) and a lower type number (P=0.0074; odds ratio=0.64). For barrows, no significant parameters were revealed. These results suggest that the variability in incidence of blood splashes can be explained by the variability of current density depending both on sex and body characteristics. Thus, electrical stunning can be improved by providing an energy level, based on the body characteristics of the pig.     

不同屠宰方式对新疆多浪羊肉品质的影响

以新疆多浪羊为研究对象,对比分析传统屠宰（对照）和3 个不同电压（90、127 V和220 V）击晕屠宰 （分别计作EST 90、EST 127、EST 220）对多浪羊肉品质的影响。结果表明：EST 90处理组成熟过程中pH值下降 速率最快,血液中的皮质醇浓度、肌酸激酶和乳酸脱氢酶活力最高,羊应激反应最剧烈,宰后1、7 d的蒸煮损失率 最高（P＜0.05）;EST 127处理组的持水力最好;电击晕对多浪羊肉嫩度有一定影响,宰后7 d各处理组嫩度显著 改善,而EST 127处理组表现最佳;EST 220处理组放血不充分,且胴体表皮有多处血斑形成;电击晕屠宰对多浪羊 肉色泽无显著影响（P＞0.05）。综合分析实验结果,EST 127处理组持水力与嫩度较优,羊应激反应较小,肉品质 相对较好,因此EST 127处理适合应用于多浪羊的屠宰加工。     

Influence of gas stunning and halal slaughter (no stunning) on rabbits welfare indicators and meat quality

This study assessed the effect of gas stunning which has not been conducted until now in comparison with slaughter without stunning on the welfare and meat quality of rabbits. Eighty male New Zealand White rabbits were divided into two groups of 40 animals and subjected to either halal slaughter without stunning (HS) or gas stunning using 61.4% CO₂, 20.3% oxygen and 18.3 % nitrogen (GS). Analysis of the sticking blood revealed that both slaughter procedures caused a substantial increase in the levels of catecholamines, hypercalcemia, hyperglycemia, lactic acidemia and an increase in enzyme activities. The ultimate pH of the Longissimus lumborum muscle did not differ between treatments. GS exhibited higher lightness and cooking loss, and lower glycogen and MFI than HS. This indicates that both GS and HS can be significant stressors although the amount of stress may be below the threshold to negatively affect rabbit meat quality.     

Post mortem energy metabolism and meat quality of porcine M. longissimus dorsi as influenced by stunning method - A (31)P NMR spectroscopic study

Post mortem changes in phosphorus metabolites and pH were studied in M. longissimus dorsi from pigs (n=10) stunned either by CO(2) (n=3), electrical (n=2), captive bolt pistol (n=2) or by anesthesia (ketamine) (n=3). (31)P-NMR spectroscopy revealed significant effects of stunning method on changes of the various phosphorus metabolites in the muscle post mortem, with the effect being most pronounced on the degradation of phosphocreatine (PCr). Moreover, the four stunning methods gave rise to large differences in the progress of pH as determined by (31)P-NMR spectroscopy. Using anesthesia as the reference showed that the captive bolt pistol caused the highest rates of post mortem degradation of phosphorus metabolites, electrical stunning intermediate, and CO(2)-stunning causing the lowest post mortem degradation rates, even though CO(2)-stunning also was associated with higher post mortem degradation rates compared with anesthesia. Finally, it was demonstrated that the water-holding capacity (WHC) of the meat was affected by the applied stunning method, as CO(2)-stunning, electrical stunning and captive bolt pistol resulted in mean drip losses of 6.4, 8.3 and 8.6%, respectively (P=0.02). The result displays the significance of induction and progress in post mortem changes on WHC in meat.     

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively?- means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.