Effect of cardiac arrest on susceptibility to carcass bruising in sheep

The effect of inducing a cardiac arrest at electrical stunning on the susceptibility of the carcass to bruising was evaluated in thiopentone-anaesthetised sheep. Bruising was induced with a percussion pistol and measured in terms of meat appearance and extractable haem pigment. Cardiac arrest caused a prompt and marked reduction in susceptibility to bruising, and it is concluded that stunning techniques which cause simultaneous heart failure could help to reduce the incidence of carcass bruising. Exsanguination of sheep which had a normal cardiac rhythm prevented the induction of bruising once 50% of the total blood loss had occurred.     

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.     

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.     

Effect of slaughter method on bleeding efficiency in chickens

The effect of inducing a cardiac arrest, at stunning, on the weight of blood collected at slaughter was examined in broiler chickens when using seven different neck cutting methods. Cardiac arrest resulted in a slower initial rate of bleeding for each neck cutting method, but by 2.25 min after neck cutting there was no effect on the amount of blood collected. The cardiac arrest treatments were associated with a higher incidence of haemorrhaging in the wings.     

Electroencephalographic studies of stunning and slaughter of sheep and calves- Part 3: The duration of insensibility induced by electrical stunning in sheep and calves

The duration of insensibility produced by electrical and percussive stunning was studied in sheep and calves. Insensibility was determined from the study of electroencephalograms (EEG) and concurrent observations were made of the reflexes and reactions of the animals. The effect of stunning on the circulation was assessed from electrocardiograms (ECG) and femoral blood pressures (BP). Electrical stunning of sheep by electrodes to the head only produced a period of reversible insensibility of 18-42s. This technique also caused an immediate and prolonged increase in BP. Electrical stunning of both sheep and calves by a 'head to back' method, which causes concurrent cardiac dysfunction, produced immediate and permanent insensibility associated with cessation of circulation and an immediate drop in BP. The use of a non-penetrative method of percussion stunning caused immediate insensibility and an increase in BP which persisted after exsanguination had commenced. Calves stunned with a penetrating captive bolt showed immediate and permanent insensibility and the EEG became isoelectric within 15 s.     

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.     

Prevalence of Escherichia coli O157 and levels of aerobic bacteria and Enterobacteriaceae are reduced when hides are washed and treated with cetylpyridinium chloride at a commercial beef processing plant

The objective of this experiment was to test the potential of a combined water wash and cetylpyridinium chloride (CPC) treatment as a hide intervention applied to cattle in the holding pens of a processing plant immediately before stunning. Over 2 processing days, 149 control and 139 treated cattle were tested. Control cattle were processed in the normal manner. The treatment group was prewashed with water the day before harvest. Immediately before stunning, these cattle were sprayed twice with 1% CPC, first for 3 min, then for 1 min. Hides and preevisceration carcasses were sampled to determine aerobic plate counts, Enterobacteriaceae counts (EBC), and Escherichia coli O157 prevalence. The treatment reduced the prevalence of E. coli O157 on hides from 56% to 34% and the prevalence on preevisceration carcasses from 23% to 3%. The treatment decreased aerobic plate counts from 4.9 log CFU/100 cm2 to 3.4 log CFU/100 cm2 and EBC from 3.1 log CFU/100 cm2 to 2.0 log CFU/100 cm2 on preevisceration carcasses. The treatment of hides did not result in any detectable CPC contamination of the chilled carcasses. These data indicated that a 1% CPC treatment preceded by a water wash was capable of reducing hide prevalence of E. coli O157 from as high as 80% to less than 50%, resulting in preevisceration carcass prevalence of 5% or less. We conclude that water washing followed by an antimicrobial treatment, such as CPC, has great potential as an effective hide intervention step and should be further evaluated for implementation as a processing step after stunning and before hide removal.     

Spread of marker bacteria from the hides of cattle in a simulated livestock market and at an abattoir

The spread of microbial contamination on the hides of beef was investigated at two stages in the meat chain: (i) in a simulated livestock market ("the market") using 33 animals, and (ii) in the unloading-to-skinning area of a commercial abattoir using 18 animals. At both stages, harmless bacterial markers (nalidixic acid-resistant Escherichia coli K-12; rifampicin- and nalidixic acid-resistant Pseudomonas fluorescens; and a tetracycline-resistant E. coli) were inoculated on the hides of a small number of selected animals, and their transfer to other animals and the environment was examined. At the market, the initial prevalence of animals positive for the hide markers (9.1% in each phase) introduced in the presale pen, sale ring, and postsale pen changed to 39.4, 15.1, and 54.5%, respectively, by the end of the market process. In addition, widespread contamination of the market environment with the hide markers was observed. At the abattoir, the initial prevalence of animals positive for the hide marker (11.1%) inoculated at unloading increased to 100% (hide before skinning) and 88.8% (skinned carcass). In addition, another marker inoculated on environmental surfaces in lairage pens, races, and stunning box was detected on 83.3% (hide before skinning) and 88.8% (skinned carcass). These results, although obtained with a relatively small number of animals, demonstrate that both the livestock market process and the unloading-to-skinning process at abattoirs can facilitate the extensive spread of microbial contamination on hides not just within, but also between, batches of animals.     

Lipid Characterization of Longissimus and Biceps Femoris Muscles from Beef Animals Exsanguinated at Various Times after Stunning

Lipid characteristics of bovine longissimus and biceps femoris muscle from 30 heifer carcasses which were exsanguinated 0 (control), 3 or 6 min after stunning were studied. Blood loss was greater when control animals were compared to animals stunned 3 or 6 min prior to exsanguination. However, total lipid, lipid phosphorus, cholesterol values and TBA numbers were similar among treatments. As time between stunning and exsanguination increased, monounsaturated and polyunsaturated fatty acids tended to increase. Delaying time between stunning and exsanguination had little influence on lipid characteristics of muscle even though large differences between lipid characteristics of muscle and blood exist.     

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.     

Effects of long- or short-haul transportation of slaughter heifers and cattle liner microclimate on hide contamination with Escherichia coli O157

Effects of cattle transportation on hide contamination with Escherichia coli O157 have been variable, and the present study was designed to clarify relationships among duration of transport, microclimate, and environment within the trailer and contamination of hides with E. coli O157. Crossbred Angus heifers from a feedlot in southern Alberta were sorted into 10 replicate loads containing 45 animals (short haul, 621.5 ± 2.1 kg of body weight) or 46 animals (long haul, 576.0 ± 1.7 kg of body weight). Long-haul trips (n = 5) were made in July and August to slaughter plant A, whereas short-haul trips (n = 5) were made in October to slaughter plant B. The same trailer unit and driver were used for all loads. Data loggers were located in the ceiling of each compartment of the trailers to record ambient temperature and relative humidity. Each heifer was swabbed on the perineum on-farm prior to loading and immediately after stunning at the slaughter plant (an average 12-h transport for long haul and 1-h transport for short haul). Swabs were transported on ice before immunomagnetic separation for detection of E. coli O157. Transportation did not affect prevalence of hide contamination with E. coli O157, although 80% of long-haul swabs were positive on-farm compared with 26% of short-haul swabs, due to seasonality of shedding E. coli O157. Cattle transported in the nose compartment had fewer positive hide swabs (P < 0.05) than cattle in the deck or belly compartments during long-haul trips, even though the nose had a higher (P < 0.05) temperature-humidity index than the other compartments. Prevalence of hide contamination varied widely among loads even when the organism was at seasonally low levels. This suggests that the feedlot pen has a greater effect on hide contamination at the slaughter plant than transportation factors including temperature-humidity index, loading density, and duration of transport.     

Influence of delayed bleeding on sensory characteristics of beef

Sensory characteristics of bovine longissimus dorsi and biceps femoris muscles from 30 heifers exsanguinated 0, 3 or 6 min after stunning and 36 steers exsanguinated 0, 3 or 30 min after stunning were evaluated to determine if delayed bleeding influenced palatability. More blood was retained in carcasses of animals where exsanguination was delayed after stunning than in control animals, but no consistent differences existed for total pigment or per cent hemoglobin in muscle. Tenderness, juiciness, flavor, shear values and cooking loss were not affected by treatment.     

Effect of electrical stunning methods on petechial haemorrhages and on the blood pressure of lambs

Electrical stunning of lambs to render them unconscious and insensible to pain can result in blood splash (spots of blood in muscles) or speckle (petechial haemorrhages in fat or connective tissue overlying the muscle). Stunning through electrodes applied to the head causes mainly blood splash with some speckle, while currents applied head-to-back or head-to-foreleg can produce speckle without blood splash. To identify the causes of speckle, animal movement and blood pressure changes that occur during stunning were measured. Three different stunning methods were employed: head-only, head-to-back and head-to-foreleg. Head-only stunning, which does not stop the heart and produces a moderate amount of speckling, was accompanied by elevated arterial blood pressures up to 300 mm Hg, and venous pressures up to 100 mm Hg. The carcass became rigid on stunning but reflex kicking occurred when the hind legs were shackled. Head-to-back stunning, which stops the heart, produced a momentary arterial and venous blood pressure rise during the stun, as a result of thoracic pressure changes, followed by a decline in pressure to 40-50 mm Hg. The muscles became markedly rigid due to direct stimulation of the loin and spontaneous kicking was absent following current switch off, although spontaneous coughing persisted. Stillness associated with head-to-back stunning was accompanied by the highest incidence and severity of speckling, whereas head-to-foreleg stunning, which also stops the heart, resulted in less muscle contraction and was accompanied by the least incidence and severity of speckling. Kicking was also eliminated if sufficiently high currents were used. Stopping the heart with KCl before a head-to-back stun lowered arterial blood pressure to 20-30 mm Hg and markedly reduced speckle. Abolition of nervously mediated muscle movement with curare before stunning resulted in no observable speckle in head-only stunned lambs but, in the head-to-back stunned lambs, there was a low incidence of speckle in the loin as a result of the muscle being directly stimulated to contract. The results from this study are consistent with the view that speckle is a result of vigorous movements between muscles during stunning, causing a shearing and rupture of blood vessels in the fat and connective tissues, thus allowing the muscles to squeeze out blood. The incidence of speckle does not appear to be related to blood pressure during stunning.     

Relationships between time of stunning and time of throat cutting and their effect on blood pressure and blood splash in lambs

A study based on 84 electrically stunned lambs showed that those gash stuck (transverse incision of the extended neck which almost simultaneously severs the trachea, oesophagus, common carotid arteries and jugular veins and the spinal cord at the occipito-atlantal junction; Blackmore & Newhook, 1976) immediately after removal of the electrical applicator had a lower incidence of blood splash than lambs gash stuck 5-8 sec r stunning. Lambs whose throats were cut immediately before the application of the electrical current had the lowest incidence of blood splash. None of the splash observed was of commercial significance. Systolic blood pressure recordings were made on a further 12 lambs of a similar age, 10 of which were electrically stunned and two shot with a captive bolt pistol. Blood pressure changes observed were related to the blood splash results obtained in the first trial. Electrical stunning raised blood pressures to an average of 3·5 times normal in lambs allowed to recover from stunning. A further seven young unweaned lambs which were electrically or percussion stunned showed a similar pattern of blood pressure change to that reported for older lambs following stunning, except that lower maximum pressures were reached. The authors interpret the results of the present trials as indicating that the application of electrical current to the heads of lambs results in damage to small vessels prior to the elevation of blood pressure. This damage may become apparent in the dressed carcass and organs as small haemorrhages. The subsequent rise in blood pressure following stunning then exacerbates the leakage of blood into tissues and it becomes more apparent in the form of discrete haemorrhages or blood splash.     

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.     

Jugular blood flow in calves after head-only electrical stunning and throat-cutting

Jugular flow was measured after head-only electrical stunning and gash cutting in 12 calves less than a week old. Jugular flow was assumed to provide a crude measure of cerebral perfusion during exsanguination. In 10 animals the average amount of jugular blood collected within 1-2 min of throat-cutting was the equivalent of a total cerebral blood flow of 3·6 ml/min/100 g ± 1·4 SD or 4·8% of normal. In two animals the jugular flow was increased to 39% and 22% of normal cerebral flow. All animals had strong retrograde flow from the head ends of the cut carotid arteries. The dynamics of cerebral blood perfusion are discussed with reference to systemic arterial blood pressure and spontaneous cortical electrical activity, and some potentially fruitful areas of research on the humaneness of halal slaughter of cattle are proposed.     

The Jarvis Beef Stunner: Effects of a prototype chest electrode

The Jarvis Beef Stunner electrically induces a stun, cardiac arrest and spinal discharge in adult cattle by three consecutive cycles. Concerns over varying incidences of cardiac arrest and some meat quality problems prompted this study to investigate the effect of replacing the conventional brisket electrode (T1) with a prototype chest electrode, with (T2), and without (T3) spinal discharge in 287 animals in a commercial abattoir. Repositioning the electrode did not significantly affect electrical parameters in any of the cycles. All animals received a cardiac arrest as assessed by electrocardiogram. Most post-stun/kill responses were unaffected. No difference was found in the incidence of a broken femur between treatments, but haemorrhages in the sirloin were significantly reduced by the prototype electrode (left: 51.1% (T1) vs. 30.3% (T3); right: 57.6% (T1) vs. 36.4% (T3)). The chest electrode was therefore efficient at causing cardiac arrest, did not significantly affect post-stun/kill responses and reduced haemorrhaging in the high-value sirloin.     

Effect of electrical stunning method and cardiac arrest on bleeding efficiency, residual blood and blood splash in lambs

Five hundred and fifty-nine Southdown-Romney cross lambs were used in a comparison of the efficiency of bleeding animals slaughtered by one of three different methods. The main comparison was between spear stuck lambs that had been electrically stunned by either head application or a head-back method. In addition, some unstunned lambs were slaughtered by the traditional New Zealand gash cutting method, no longer used by industry but known to produce well bled carcasses. There was no difference in blood obtained during a 120-s bleeding time between the unstunned and head stunned lambs. For the head-back stunned lambs little, if any, of the blood not collected at bleeding remained in the carcass after dressing despite the fact that these animals released only 46% of the weight of blood recorded from the head stunned lambs during the bleeding time. The head-back stunning method markedly decreased the incidence of carcass blood splash in comparison with the splash observed in lambs stunned by the head application method.     

The influence of slaughter method on the residual blood content of meat

The effect of slaughter method on the residual haemoglobin content of the M. longissimus dorsi and the amount of blood lost at exsanguination of sheep was investigated. The influence of stunning method (electrical, 90 V, or captive bolt pistol), pithing and bleeding-out position were examined. Sheep bled lying lost more blood than those bled hanging and electrically-stunned animals lost more blood than those stunned with a captive bolt pistol; pithing had no effect. The residual haemoglobin content of the muscle did not vary significantly between methods and there was no relationship between it and the amount of blood lost at slaughter.     

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.