Brain tissue fragments in jugular vein blood of cattle stunned by use of penetrating or nonpenetrating captive bolt guns.

Although the incidence of bovine spongiform encephalopathy in cattle continues to decline in the United Kingdom, it remains important to maintain vigilance of all potential routes of transmission of infection to humans. Initial studies have demonstrated a potential risk of carcass contamination with brain tissue following the use of captive bolt gun stunning in cattle. The objective of this study was to further explore these initial findings particularly in regard to captive bolt guns currently in use in the United Kingdom. Brain tissue fragments or elevated levels of a marker protein for brain tissue were detected in venous blood samples from 4% (95% confidence interval, 1.6 to 9.8%) of cattle stunned by penetrating captive bolt gun and from 2% (95% confidence interval, 0.6 to 7%) of those stunned by nonpenetrating captive bolt gun.

Methods for detection of haematogenous dissemination of brain tissue after stunning of cattle with captive bolt guns.

Because of concern that the stunning of cattle with captive bolt guns (CBGs) could, if used on an animal with bovine spongiform encephalopathy (BSE), cause embolism of infective brain tissue and carcass contamination, the Ministry of Agriculture, Food and Fisheries commissioned research to assess the risk of haematogenous dissemination of CNS material after stunning. We have devised two methods to investigate this risk. The first involves the concentration of embolic tissue in buffy coat Cytoblocks that can be embedded for sectioning, microscopy and immunocytochemistry. The second method is an ELISA for the presynaptic protein, syntaxin 1B. The methods were validated by analysis of several bovine tissues, including blood samples deliberately contaminated with brain. We then studied jugular venous blood obtained before and after the stunning of 60 cattle with CBGs. Samples obtained, after stunning, from five of the cattle contained CNS tissue within the Cytoblocks and yielded positive syntaxin assays. Syntaxin was also detected in samples from one other animal that had been stunned with a pneumatically operated CBG. The described methods should allow an assessment of the risk of neuroembolism associated with different types of CBG and may also be useful in other contexts.

Dissemination of brain emboli following captive bolt stunning of sheep: capacity for entry into the systemic arterial circulation.

The epidemic of bovine spongiform encephalopathy in the United Kingdom and the recognition of a variant of Creutzfeldt-Jakob disease prompted revision of the guidelines for slaughter of cattle and sheep to prevent contamination of the edible parts of the carcass with central nervous system tissue. We previously showed that captive bolt gun stunning, which is routinely used for the slaughter of cattle and sheep, causes entry of fragments of central nervous system tissue into the jugular vein. To determine whether such tissue can traverse pulmonary capillaries to enter the systemic circulation, we introduced small volumes of brain tissue that had been disrupted by stunning with a captive bolt gun into the jugular vein of sheep sent for slaughter. We examined aortic blood samples by immunocytochemistry for neurofilament and S100 proteins and by enzyme-linked immunosorbent assay for glial fibrillary acidic protein and found fragments of neurofilament- and S100-immunopositive central nervous system tissue in samples from 2 of 11 sheep and elevated glial fibrillary acidic protein in 6 sheep. Our findings suggest that central nervous system tissue that is dislodged during routine captive bolt gun stunning and slaughter of sheep can enter the systemic arterial circulation and that, in some cases, this method of slaughter of an animal infected with bovine spongiform encephalopathy would be likely to contaminate edible parts of the carcass with infective material.

Variations in electrical stunning tong placements and relative consequences in slaughter pigs.

Variations in the manual application of electrical stunning tongs that are commonly observed in stunning pens in abattoirs were tested under laboratory conditions on 145 pigs. Five different placements, previously identified during a survey, using either 150 or 250 V were studied, and the welfare consequences and effects on the intensity of carcass convulsions were assessed. Quantitative relationships between tong applications, average current strength, prevalence of induction failure, indicators of insensibility and signs of recovery were evaluated. Those placements not spanning the brain were found to be inadequate on welfare grounds when used at 150 or 250 V. The variation in convulsion intensity, subjectively scored, was small and therefore it is unlikely that tong position using a 50 Hz alternating current (AC) is an important factor influencing carcass handling. The need to develop methods for reliably measuring currents going through the brain is emphasized.

Studies on the return of physical reflexes in pigs following electrical stunning.

In order to obtain quantitative information on the duration of insensibility in pigs (60-80 kg) following electrical stunning, experiments were carried out using 50 Hz alternating current for 3 and 7 s current durations at different voltages. The following features were examined: the mean current received by each pig, the period of loss of reflexes and the time to return of spontaneous activity, and cranial nerve reflexes. In particular the return of breathing was used as a first sign of recovery, and the response to a nose prick and presence of the righting reflex were used as indicators of overt consciousness. A minimum current in excess of 406 mA was required to effectively stun these pigs with sufficient duration of loss of reflexes. At least 150 V for 3 s current duration should be used and a maximum stunning to exsanguination interval of 15 s is considered sufficient to ensure pigs of this size do not regain consciousness following the stun.

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.

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 effect of the sticking method on the welfare of slaughter pigs.

A project was undertaken to investigate the causes of inadequate sticking encountered during a survey of pig abattoirs. The results of the investigation identified the length of the sticking (exsanguination) wound as a major contributor to the problem. Experimental abattoir trials conducted on slaughter pigs comparing two sticking lengths indicated that the rate of bleed out was delayed with short sticking wounds. In addition, information about the identity of blood vessels severed following sticking was obtained. The results indicate that following head-only electrical stunning, a relatively long sticking wound should provide better welfare in slaughter pigs. The study has also highlighted the health and safety problems for the operatives as well as the welfare concerns associated with manual application of electrical stunning.

Electrical stunning in commercial rabbits: Effective currents, spontaneous physical activity and reflex behaviour.

Electrical stunning was evaluated in commercial slaughter rabbits. Different voltage applications with varying current duration were tested in recovery experiments in 71 animals. Stunning parameters and duration of insensibility were measured and analysed for assessing stunning effectiveness. A minimum stunning current of 140 mA which can be achieved with application of 100 V was recommended.

Pig slaughtering procedures: Head-to-back stunning.

High voltage head-to-back electrical stunning can induce vertebral compression fractures, blood splash and poor meat quality in pigs. This experiment was designed to determine the optimum position of the rear electrode which would not only stun and kill pork and bacon weight pigs with a 1·3 A 50 Hz sinewave but would also produce a good carcass with desirable meat quality. Although there was a trend for less breaks to occur the further forward the rear electrode was positioned, there was no position which gave 100% cardiac fibrillation and an absence of breaks. The incidence of blood splash, muscle haemorrhages and the variations in meat colour were not related to electrode position and fell in the 'normal' range quoted by other workers. The severity and incidence of kicking after stunning was reduced the more caudal the electrode position. This was in direct contrast to the effect on compression fractures where a reduction was seen with the more rostral applications.

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.

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.

Broiler stunning and meat quality.

The effects of electrical and concussion stunning on meat and carcass quality of broilers were compared. Broiler chickens (n = 165) were subjected to treatments: 1) electrical stunning with no fibrillation, 2) electrical stunning with fibrillation, 3) concussion stunning with restraint, or 4) concussion stunning with no restraint. Electrical stunning (100 V, 80 mA, 50 Hz sinusoidal waveform alternating current) was applied for 3 s. Concussion was applied using a nonpenetrative captive bolt gun with or without restraint. We assessed broken bones, hemorrhages, meat quality defects, blood loss, pH at 10 min and 24 h, and texture from breasts filleted 3 h and 24 h postmortem. Electrically stunned birds showed a significantly higher incidence of broken bones (P < 0.0001), coracoid and furculum bone hemorrhages (P < 0.0001), and nonbone hemorrhages (P < 0.0001) than birds stunned by concussion. However, the incidence of red wing tips (P < 0.005) and shoulder hemorrhages was significantly higher (P < 0.05) in concussion-stunned birds than electrically stunned birds. Electrically stunned and nonfibrillated birds had the fastest blood loss rate. The pH value at 10 min was the lowest in concussion-stunned and unrestrained birds. Breast muscles from concussion-stunned birds that were filleted at 3 h postmortem were more tender than those from birds stunned electrically (P < 0.05). We concluded that concussion stunning could be advantageous for early filleting.

Reflexes and loss of sensibility following head-to-back electrical stunning in sheep.

The effects of head-to-back electrical stunning on the incidence of post-stunning reflex activity and cortical evoked responses were investigated in sheep. The stuns were effective in terms of inducing epileptiform activity and they resulted in cardiac fibrillation which ensured that there was no recovery of consciousness. Even though the corneal reflex and respiratory gasps were present, in 10 out of 12 sheep there were no concomitant visual and somatosensory evoked responses following a stun. In the remaining two, the responses were rudimentary and it would be unwise to conclude that the animals were conscious. It is suggested that brain stem reflexes following this stunning method should not be relied on as indices of recovery. The results support the view that an electrical stunning method which induces cardiac fibrillation results in improved animal welfare.

Time in lairage needed by pigs to recover from the stress of transport.

Two experiments were carried out in which a total of 602 pigs were slaughtered after being held in lairage for periods ranging from less than one hour to 21 hours. In the first experiment the pigs were handled under ideal conditions and slaughtered at the University of Bristol slaughterhouse; in the second the pigs were killed at a commercial plant. Blood samples collected at exsanguination were analysed for indices of stress. There were no consistent effects of time in lairage on the levels of lactate and creatine phosphokinase. Plasma cortisol and beta-endorphin levels were reduced by lairage for three hours or more in the first experiment and cortisol was reduced by lairage for two hours or more in the second; beta-endorphin was not measured in the second experiment. A period of rest in lairage allowed the pigs to recover from transport and the associated handling and the recovery appeared to be complete within two to three hours.

Long distance transport of lambs and the time needed for subsequent recovery.

The effects of nine and 14 hours of road transport and the subsequent recovery in lairage of 392 hill lambs were studied in August and November. The gathering and the handling of the lambs were stressful, both physically and psychologically, and the journey imposed further psychological and metabolic stress. The levels of noise in the trailer were high (90db[A]). There were no measurable differences between the responses of the lambs transported for nine or 14 hours and there appeared to be three stages in their recovery after transport. After the first 24 hours of lairage changes in the blood components usually associated with short term stress and dehydration had recovered; after 96 hours there had been a well defined recovery of liveweight and the levels of most of the metabolites measured appeared to have stabilised and after 144 hours the lambs had recovered almost completely, most of the creatine phosphokinase had been cleared from the plasma and their plasma protein levels had stabilised.

Jugular venous emboli of brain tissue induced in sheep by the use of captive bolt guns.

Emboli of central nervous tissue were detected in the jugular venous blood of two of 15 sheep stunned with a conventional cartridge-operated captive bolt gun and in two of 15 sheep stunned with a pneumatically activated gun. No emboli were detected in arterial blood from these sheep or in venous blood from sheep stunned electrically. Emboli from an animal with BSE could transmit the disease to people.

Religious slaughter: evaluation of current practices in selected countries.

As part of the project "Religious slaughter (DIALREL): improving knowledge and expertise through dialogue and debate on issues of welfare, legislation and socio-economic aspects", this paper discusses an evaluation of current practices during Halal and Shechita slaughter in cattle, sheep, goats and poultry. During religious slaughter, animals are killed with and without stunning by a transverse incision across the neck that is cutting the skin, muscles (brachiocephalic, sternocephalic, sternohyoid, and sternothyroid), trachea, esophagus, carotid arteries, jugular veins and the major, superficial and deep nerves of the cervical plexus. In this report, the restraint methods, stunning, neck cutting, exsanguination, slaughter techniques and postcut handling in the abattoir were assessed for religious slaughter. Information about the procedures used during religious slaughter in Belgium, Germany, Italy, the Netherlands, Spain, the UK, Turkey and Australia was collected by means of spot visits to abattoirs. To standardize the information gathered during the spot visits three guidelines were designed, one for each species, and translated into the national languages of the countries involved. The document included questions on the handling and restraint methods (stunning, neck cutting/exsanguination/slaughter techniques and postcut handling performed under religious practices) and for pain and distress of the animal during the restraint, neck cutting and induction to death in each abattoir. Results showed differences in the time from restraining to stun and to cut in the neck cutting procedures and in the time from cut to death.