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.     

Evaluation of electrical stunning in commercial rabbits effect on brain function

Effect of electrical stunning on brain function in commercial rabbits was evaluated in electrophysiological studies. In addition to measuring duration of spontaneous physical activity and times to signs of recovery, electrocorticogram (ECOG) recordings and evoked responses were analysed following electrical stunning with 100 V for 1 s in eight rabbits. Epileptiform and other types of activity indicating insensibility were observed in the ECOG. Evoked responses were absent from 24 to 204 s following stunning. Application of a minimum current of 140 mA followed by prompt sticking should prevent welfare problems at stunning and slaughter in rabbits.     

The effectiveness of high frequency electrical stunning in pigs

Two commercially-available high frequency electrical stunners producing either AC sinewaves (146 V; 1592 Hz) or DC squarewaves (162V; 1642 Hz) having different waveforms were tested for their effectiveness in stunning pigs and compared with conventional 50 Hz sinusoidal waveforms. Seventy-nine pigs were stunned using the highest voltage settings, allowed to recover, and the duration of insensibility was assessed from behavioural signs. It was found that the pigs were adequately stunned by this method even though some physical responses differed from 50 Hz stunning. An additional experiment was conducted on three pigs to examine whether the epileptic brain activity (indicative of unconsciousness) occurred following high frequency stunning and to assess the effects on visually evoked responses. It was confirmed that high frequency stunning produced epilepsy and unconsciousness and appeared therefore to be acceptable from an animal welfare standpoint. However, the average stunning to sticking intervals were shorter with high frequency stunning compared with 50 Hz stunning.     

The effect of repeat application of electrical stunning on the welfare of pigs

Although legislation requires the production of immediate insensibility, implying that a stun can be applied only once, the practice of repeat application of electrical stunning is common. However, the relative consequences of such repeat applications are unknown. This study investigated the effects of repeat applications of electrical stunning (200 V, 50 Hz) following different delays of 15, 60 or 180 s between the initial stun and the repeat applications. The parameters examined, following stunning, were the durations of spontaneous physical activity, time to return of reflexes and the duration of the epileptiform activity in the electrocorticogram. The results showed that repeat application of electrical stunning can produce successive epileptic activity and therefore an effective stun. The duration of tonic and clonic phase activity following repeat application was significantly shorter than after a single stun only. There was a tendency for the reflexes to return more quickly following repeat application. The use of electrical stunning to re-stun pigs appears to raise no welfare concerns and although commonly used, should only be applied out of necessity rather than as routine practice.     

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...     

Animal welfare at markets and during transport and slaughter

This review highlights some recent developments in our understanding of stress and physical injuries that occur before and during transport to slaughter, during handling at livestock markets, and at the time animals are put-up for slaughter within abattoirs. Stress in pigs during transfer to the stunning point within the abattoir has important effects on meat quality, and there is growing evidence that strenuous exercise or CO(2) stunning can contribute to oxidative rancidity in pigs, poultry and fish. In the EU, putting cattle through a crush in order to check that their eartag numbers correspond to their passport numbers is imposing additional stress, and there are reports that it is leading to greater hide contamination with Escherichia coli O157. Recent developments in stunning and slaughter include a better understanding of the causes of variation in captive bolt gun performance, the effectiveness of poll instead of frontal shooting in water buffalo, the prevalence of false aneurysms in carotid arteries during shechita and halal slaughter, and the stress effects of CO(2) stunning in fish. Stunning pigs with 90% CO(2) leads to less PSE meat than 80% CO(2). There have been concerns about the physical activity that cattle show following electrical stunning with an electrically induced cardiac arrest, and with electrical stunning using DC waveforms in broiler chickens. There is also growing concern about the hygiene problems that exist in wet markets, where animals are slaughtered alongside meat that is on display to customers.     

Welfare of calves - 2. Increase in vertebral artery blood flow following exsanguination by neck sticking and evaluation of chest sticking as an alternative slaughter method

The role of the vertebral arteries in delaying loss of sensibility following neck sticking in slaughter calves was investigated. Vertebral artery blood flow was measured using probes before, during and after electrical stunning and slaughter. Systemic blood pressure, electrocorticogram, visually evoked responses and the occurrence of carotid occlusions were also recorded. When carotid occlusion occurred, the time to onset of brain failure was delayed based on the development of an isoelectric state. In addition, when carotid occlusion occurred the mean arterial blood pressure was sustained for longer following slaughter, and concurrently vertebral artery blood flow could be maintained at about 30% of its initial level for up to 3 min. In some animals vertebral artery flow increased substantially following sticking. When chest sticking was used no occlusion of vessels occurred, mean arterial blood pressure fell promptly (within 8 s) and the onset of an isoelectric state did not extend beyond one minute. In addition, visually evoked responses were not present after 5 s following chest sticking.     

Welfare of calves - 1. Investigations into some aspects of calf slaughter

The relationship between carotid occlusion, systemic blood pressure and brain function following electrical stunning and exsanguination (sticking) in slaughter calves (< 10 weeks) was assessed. Electrocorticograms, systemic blood pressure and evoked responses were measured in the chloralose. anaesthetised and the unanaesthetised states. Electrical stunning produced relatively short periods of measurable epilepsy in slaughter calves (18 s average). The pattern of decline in blood pressure after sticking showed variations between animals. However, the results indicated that two groups of animals could be recognised: a carotid occlusion (ballooning group) and no carotid occlusion (non-ballooning) group. The animals with ballooning (six out of 15 = 40%) developed occlusions of the caudal severed ends of the carotid arteries. These swellings, the so-called 'ballooning' effect, were characterised by large clots forming plugs at the severed ends of the arteries. When this phenomenon occurred the haemorrhaging was clearly impeded. This was reflected in the blood pressure traces which showed recovery episodes coinciding with the occurrence of the carotid occlusions. Our study indicates that in the worst possible case the development of a restriction to the outflow of blood can delay the rate of haemorrhaging and the decline in blood pressure. This can lead in turn to sustained brain function as evidenced by the continued presence of evoked responses following stun recovery and a long time to onset of the isoelectrical state in the electrocorticogram.     

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.     

Chemical and physiological aspects of pig stunning in relation to meat quality-A review

A survey of research undertaken at the Research Institute for Animal Husbandry 'Schoonoord' is given in which different stunning methods have been evaluated with respect to metabolic, meat quality and economic aspects. These data have been supplemented from the literature. The overall conclusion is that electrical stunning (300V) with short stunning time and a minimal lapse of time between stunning and sticking, offers the best prospects in relation to pork quality. Electrical stunning is thus recommended for pigs in industrial scale slaughtering.     

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.     

The influence of the rate of pH decline on the rate of ageing for pork. I: interaction with method of suspension

The influence of the rate of pH decline post slaughter on the rate of ageing of pork was investigated. The rate of pH decline on 24 finisher pigs was manipulated by altering the method of stunning (carbon dioxide or electrical head to heart) and by the use of electrical stimulation (none or low voltage electrical stimulation (LVES) at 4 min post slaughter). To investigate the effect of pH decline rate on ageing rate independently of the effect on possible muscle shortening, sides were suspended by either the pelvis (to minimize shortening) or conventionally by the Achilles tendon. The data indicated that the rate of pH decline did not influence the rate of ageing but the use of LVES did improve tenderness at 1, 2 and 10 days post slaughter due to the prevention of muscle shortening. Electrical stunning improved tenderness at 1 and 2 days post-slaughter but had a detrimental effect on drip loss. Pelvic suspension improved tenderness at rigor, 1, 2 and 6 days post slaughter due to prevention of muscle shortening. The conditions employed however were not severe enough to induce protein denaturation.     

Stunning and animal welfare from Islamic and scientific perspectives

The transformation of an animal into pieces fit for human consumption is a very important operation. Rather than argue about halal slaughter without stunning being inhumane or stunning being controversial from the Islamic point of view, we discuss slaughter, stunning and animal welfare considering both Islamic and animal welfare legislation requirements. With the world Muslim population close to two billion, the provision of halal meat for the Muslim community is important both ethically and economically. However, from the animal welfare standard point of view, a number of issues have been raised about halal slaughter without stunning, particularly, about stressful methods of restraint and the latency of the onset of unconsciousness. This paper sets out to, discuss the methods of stunning that are acceptable by Islamic authorities, highlight the requirements for stunning to be acceptable in Islam and suggest practical ways to improve the humanness of slaughter.     

Electrical stunning by direct brain stimulation in pigs

The effects of electrical stunning of slaughter pigs by electrodes shot into the brain, on sensibility and on the incidence of haemorrhages in the shoulder postmortem, were studied.

To determine the efficiency of this method 37 slaughter pigs were equipped with EEG (electroencephalograph) and ECG (electrocardiograph) electrodes and stunned twice via the EEG electrodes. In the first experiment the pigs were stunned with 25 V and in the second with 25 V followed by a relaxation current. The day after slaughter the shoulders were scored for haemorrhages. Under more practical conditions three groups of 10 pigs each were electrically stunned via electrodes shot into the brain using 25, 50 or 75 V, followed by a relaxation current. The day after stunning the shoulders were scored for haemorrhages.

The pigs did not react to shooting electrodes frontally into the head. After stunning all animals showed a general epileptiform seizure. However, after the second stun the tonic and clonic muscle cramps were impaired. The heart rate increased significantly (P < 0·01) after stunning, and extra systolae and irregular heart rates were observed. In the shoulders of 27% of the carcasses no haemorrhages were found and in the remainder only minor haemorrhages were seen. Under practical conditions a voltage of 87(± 2) V and a current of 511(±20) mA seemed to be necessary for an effective stun. When lower voltages were applied fewer carcasses with shoulder haemorrhages were found.

It may be concluded from these experiments that 25 V (134 mA; 150 Hz) is sufficient for effective stunning of slaughter pigs when electrodes are in direct contact with the brain. But as the optimum position of the electrodes may not be reached under practical conditions a voltage of approximately 90 V (550 mA; 150 Hz) is recommended. After this stunning method only a few haemorrhages were observed in the shoulders.     

Effect of stunning conditions on occurence of PSE defects in hams of rn+/RN(-) pigs

Pigs of the same genetic type at the RN and HAL loci, i.e. rn⁺RN⁻/NN were reared in similar conditions of feeding and housing. They were slaughtered in two abattoirs (referred to as A1 and A2) using a mixture of air (30%) and CO₂ (70%), at a rate of 300 pigs per hour per slaughterline. One hundred and thirty-two pigs from 11 farms were slaughtered in A1 using a corusinga restrainer and 127 pigs from 5 farms were slaughtered in A2 with the backloading technique. pH at 40 min, 2.5 h and 24 h after slaughter and colour (L*, a*, b*) at 24 h after slaughter were measured in the semimembranosus muscle. Meat quality of the ham was scored as follows: 1, no PSE-zone; 2, doubtful; 3, PSE-zones in the semimembranosus and sometimes on the internal flexor muscles; 4, PSE-zones in all the flexor muscles. The muscle pH value was higher in A2 than in A1 at 40 min post mortem (P<0.01), but not at 2.5 and 24 h. L* (P<0.001) and b* (P<0.05) were higher in A1 than in A2. There was a remarkable difference in meat quality scores, with 50% of the hams scoring 3 or 4 in A1, vs 13% in A2. Lairage time before slaughter affected (P<0.01) the pH value at 2.5 h (5.69 vs 5.93). The values of pH1 and pH2.5 decreased with increasing the meat quality score. The values of L* and b* increased markedly with the score. The results of the present study indicate that the method of bringing the slaughter pigs to the stunning device affects the frequency and importance of PSE meat in the ham. The automated driving of groups of animals to the stunning machine combined with the backloading of a nacelle, compared to a traditional system driving pigs in single file using electrical goads and a restrainer was beneficial with respect to both meat quality and animal welfare.     

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).     

Blood in the respiratory tract during slaughter with and without stunning in cattle

Bovine respiratory tracts were examined for blood following shechita without stunning, halal slaughter without stunning, and captive bolt stunning with sticking. In all three methods the cattle were in the upright (standing) position at the start of bleeding. Those that had not been stunned continued to breathe during the early part of bleeding whilst those that were stunned were not breathing. Nineteen percent of the shechita, 58% of the halal and 21% of the stunned plus stuck cattle had blood lining the inner aspect of the trachea. Thirty six percent, 69% and 31% had blood in the upper bronchi, respectively. Ten percent, 19% and 0% had fine bright red blood-tinged foam in the trachea, respectively. It was concluded that concerns about suffering from airway irritation by blood could apply in animals that are either not stunned before slaughter or do not lose consciousness rapidly whilst blood is present in the respiratory tract.     

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.     

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.