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.     

Effectiveness of poll stunning water buffalo with captive bolt guns

Practical experience has indicated that shooting water buffalo with a captive bolt gun in the front of the head does not always produce an effective stun. Slaughtermen have been claiming that the poll position is more reliable, but under present EU regulations this shooting position is not allowed for domesticated bovines. This study examined the effectiveness of shooting water buffalo with captive bolt guns in the poll region. The depth of concussion was assessed in 30 water buffalo from physical collapse, presence or absence of corneal and palpebral reflexes, normal rhythmic breathing, eyeball rotation, nystagmus and whether the animal was re-shot. All except one animal collapsed immediately. The one animal that failed to collapse was not breathing. The prevalence of a shallow depth of concussion in the poll shot animals was 53%. Two had been shot through the spinal cord, and with the exception of those plus one other in which the bolt did not penetrate the brain, the other animals were considered to be adequately stunned. Post mortem examination of the brain showed that 79% of the under thirty month old animals were shot in the midbrain or brain stem, but these regions had to be avoided in over thirty month old animals because of the risk of damaging the brain stem sample needed for BSE testing. In addition, three water buffalo were shot in the crown position and one in the front of the head. The frontal position was ineffective as the animal did not collapse, and all animals shot in the crown position resumed breathing shortly after shooting, indicating a shallow depth of concussion. It is concluded that poll shooting can be effective in water buffalo, but it produces a shallow depth of concussion compared with frontal shooting in cattle. It requires accurate placement of the gun to ensure that buffalo are not shot through the spinal cord instead of the brain. Vigilance is needed in ensuring that the animals are stuck promptly so that none recover consciousness.     

The effects of electrical stunning and percussive captive bolt stunning on meat quality of cattle processed by Turkish slaughter procedures

The effects of electrical and percussive captive bolt stunning both on initial and up to 14 days post mortem meat quality of Friesian young bulls were studied. The first group (NS; n=10) were slaughtered without stunning under Turkish slaughter procedure (these animals were slaughtered under conditions acceptable to the appropriate ethics committee) in a modern abattoir. In the second group (ES; n=10) animals were electrically stunned. In the third group (PS; n=10) animals were stunned with percussive captive bolt. Meat quality was assessed by examining muscle glycogen concentration, pH and WHC. Also cooking loss, texture parameters and consumer sensory properties were assessed at 24 h, 4, 7 and 14 days post mortem. Meat colour as L^*, a^*, b^*, C^*, h^* values were evaluated at 0, 48 h, 3, 5, 7, 9 and 14 days post mortem. Pre-slaughter handling affected muscle glycogen concentration (P<0.05). Animals in electrical and percussive captive bolt stunned groups had higher muscle glycogen concentrations compared to animals in the non-stunned group (P<0.05). Although pre-slaughter handling did not affect significantly pH_{24 h} and WHC, differences were significant for cooking loss, colour coordinates and texture parameters at some storage times. For all sensory attributes (odour, flavour, tenderness and overall acceptability) at all ageing periods (24 h, 4, 7 and 14 days) the percussive stunned (PS) group was significantly superior to the non-stunned (NS) group. The electrically-stunned (ES) group also tended to be superior to the NS group although not all differences were statistically significant. These results indicate that percussive captive bolt stunning of cattle improved meat quality compared with cattle electrically stunned using head only tongs and those non stunned under approved Turkish slaughter procedure.     

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.     

A comparison of the effects of electrical, captive bolt or percussion stunning on the incidence of blood splash in lambs

Three-hundred-and-three lambs were divided into three equal groups. Half the lambs in each group were not weaned before slaughter and the weaned half were slaughtered a week later. Lambs in one group were head stunned electrically before slaughter; in the second group lambs were stunned with a captive bolt pistol and in the third group they were percussion stunned before slaughter. Carcasses, gall-bladders, hearts and duodenums were inspected for blood splash after slaughter. A few small haemorrhages were detected in 57% of the electrically stunned lambs, in 30% of the captive bolt stunned lambs and in only 16% of the percussion stunned animals. Although no splash of commercial significance was found in any carcass, 25% of the electrically stunned lambs had detectably splashed carcasses, whilst only 1% of percussion-stunned lambs had splashed carcasses with captive bolt stunned lambs being intermediate in carcass splash incidence. These results show that stunning method affects the incidence of blood splash.     

Depth of concussion in cattle shot by penetrating captive bolt

The prevalence of shallow depth of concussion following captive bolt shooting was assessed in 1608 cattle at an abattoir. Depth of concussion was determined in each animal from physical collapse, presence or absence of corneal reflex, normal rhythmic breathing, eyeball rotation, and whether the animal was re-shot. The presence of nystagmus and the absence of tongue protrusion were also monitored as potential indicators of a shallow depth of concussion, and simultaneous noise measurements assessed whether loudness of gun discharge was linked to concussion depth. The prevalence of a shallow depth of concussion was 8% for all cattle and 15% for young bulls. Nystagmus was associated with other indicators of a shallow depth of concussion. Absence of tongue protrusion was not associated with depth of concussion, but could serve as a useful indicator of jaw relaxation and insensibility following exsanguination. Soft-sounding shots (111 dB) when using 4.5 gr cartridges were associated with shallow depth of concussion.     

Arrested blood flow during false aneurysm formation in the carotid arteries of cattle slaughtered with and without stunning

The time to onset of arrested blood flow and the size of false aneurysms in the severed carotid arteries were assessed in 126 cattle during halal slaughter without stunning. Thirty six cattle (29%) showed early arrest of blood flow. In 6%, both the left and right carotid arteries in the same animal stopped bleeding before 60 s had elapsed following the neck cut. The time to early arrested blood flow was on average 21 s, and this was accompanied by enlargement with false aneurysms which occluded the arteries. In the arteries which were still bleeding at 60 s after the neck was cut the artery size was normal. Based on comparative data from different slaughter premises it appeared that making the cut in the neck at the first cervical vertebra instead of the second to fourth cervical vertebrae reduced the frequency of false aneurysm formation and early arrested blood flow. This was confirmed in a separate controlled trial where 100 cattle were stunned with a captive bolt and the arteries were examined following neck cutting at either the C1 or C3 positions.     

Depth of concussion in cattle shot by penetrating captive bolt

The prevalence of shallow depth of concussion following captive bolt shooting was assessed in 1608 cattle at an abattoir. Depth of concussion was determined in each animal from physical collapse, presence or absence of corneal reflex, normal rhythmic breathing, eyeball rotation, and whether the animal was re-shot. The presence of nystagmus and the absence of tongue protrusion were also monitored as potential indicators of a shallow depth of concussion, and simultaneous noise measurements assessed whether loudness of gun discharge was linked to concussion depth. The prevalence of a shallow depth of concussion was 8% for all cattle and 15% for young bulls. Nystagmus was associated with other indicators of a shallow depth of concussion. Absence of tongue protrusion was not associated with depth of concussion, but could serve as a useful indicator of jaw relaxation and insensibility following exsanguination. Soft-sounding shots (⩽111 dB) when using 4.5 gr cartridges were associated with shallow depth of concussion.     

Some aspects of the effectiveness of stunning in sheep by the captive bolt

The effects of penetration depth and the velocity of the bolt on the onset of unconsciousness was investigated in twenty-four sheep of about 45 kg liveweight. The sheeps' state of consciousness was judged from the electrocorticograms recorded via electrodes surgically pre-implanted frontally on the right side of the head. Sixteen sheep were trephined. A commercial captive bolt pistol and an experimental manual bolt, both with variable penetration depths, were used to represent high and low velocity stunning. Stunning by destroying only the cortex or by only penetrating the skull when the experimental bolt or captive bolt pistol, respectively, were used, did not produce unconsciousness. Unconsciousness was obtained after destroying the cortex and deeper parts of the brain with the experimental bolt (low velocity) or after destroying the cortex (and deeper parts of the brain by shockwaves) when using a captive bolt pistol (high velocity). To produce unconsciousness the captive bolt should have sufficient energy and length after penetration of the skull to crush the cortex and deeper parts of the brain, either directly or by shockwaves.     

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.     

The histology of blood splash in lamb

Ecchymosis (blood splash), can occur in the carcasses of animals that have been stunned electrically or shot with a captive bolt. While blood splash presents no health hazard, it is likely to detract from the acceptable appearance of the meat. Based on light and electron microscopic studies, ecchymosis has been shown to be due to the localised discharge of blood from ruptured blood vessels into the surrounding muscle tissue. A small proportion of muscle fibres in a splashed region were distorted ( 5 %) with irregular zones of high shortening interspersed with zones of lesser shortening. Such ‘supercontracture’ and its associated blood splash was markedly reduced by neuromuscular blocking agents. It is proposed that through supercontracture of some fibres, a severe strain is placed on adjacent blood vessels, occasionally leading to their rupture and hence to haemorrhaging.     

Bos indicus-cross feedlot cattle with excitable temperaments have tougher meat and a higher incidence of borderline dark cutters

Temperament ratings based on a numerical scale (chute score) were assessed during weighing and handling of cattle at a feedlot. Breeds studied included Braford, Red Brangus and Simbrah. Cattle were fed to a constant fat thickness of 9 to 13 mm (target = 11 mm) over the 12th rib as determined by periodic ultrasound measurements. Cattle were slaughtered in a commercial slaughter plant and stunned by captive bolt. Temperament rating had a significant effect on the incidence of borderline dark cutters which were downgraded by a USDA grader (P = 0.01). Temperament score also had a significant effect on tenderness (P < 0.001) as evaluated by Warner-Bratzler Shear (WBS) force at day 14 post mortem. The calmest animals which stood still when restrained in a hydraulic squeeze chute had a mean WBS force of 2.86 ± 11 kg and cattle which became highly agitated and struggled violently during restraint averaged 3.63 ± 19 kg. Forty percent of these cattle had WBS force values which were over 3.9 kg which is a threshold value for acceptability in food service establishments. These data show that cattle with the most excitable temperament ratings produce carcasses with tougher meat and a higher incidence of borderline dark cutters than cattle with calm temperament ratings.     

Effect of pre-slaughter handling on the quality and microbiology of venison from farmed young red deer

Young stags, castrates and hinds, raised on heathery hill pasture were subjected to three levels of stress prior to slaughter. They were either individually penned overnight and shot, confined in threes in a pen overnight and stunned by captive bolt or confined in threes in a wire fenced pen overnight and then agitated by an older deer for 2 h and finally stunned by captive bolt. Some 30% of the stag and castrate carcasses had high ultimate pH (pH_u≥6.0) and the venison from these exhibited typical dark cutting appearance. The pH_u of the hind carcasses was <5.5. Overall there was no significant difference in pH_u between stressed and unstressed groups, but the incidence of high pH_u was greatest in the severely stressed stags and castrates. Texture of roasted M. semimembranosus pH_u of <6.0 was slightly to moderately tender and the high pH_u venison was very tender. Stress level did not affect the microbiological condition of the freshly skinned carcasses or the total viable counts on joints during storage at 1°C.     

Prevalence, enumeration, and antimicrobial agent resistance of Clostridium difficile in cattle at harvest in the United States

To assess the potential for food contamination with Clostridium difficile from food animals, we conducted a cross-sectional fecal prevalence study in 944 randomly selected cattle harvested at seven commercial meat processing plants, representing four distant regions (median distance of 1,500 km) of the United States. In all, 944 animals were sampled in the summer of 2008. C. difficile was isolated from 1.8% (17 of 944) of cattle, with median fecal shedding concentration of 2.2 log CFU/g (range = 1.6 to 4.8, 95% confidence interval = 1.6, 4.3). Toxigenic C. difficile isolates were recovered from only four (0.4%) cattle. One of these isolates was emerging PCR ribotype 078/toxinotype V. The remaining toxigenic isolates were toxinotype 0, one of which was an isolate with resistance to linezolid, clindamycin, and moxifloxacin (by the E-test). All isolates were susceptible to vancomycin, metronidazole, and tigecycline, but the MICs against linezolid were as high as the highest reported values for human-derived isolates. The source of the linezolid-clindamycin-moxifloxacin resistance in a toxigenic C. difficile isolate from cattle is uncertain. However, since the use of these three antimicrobial agents in cattle is not allowed in North America, it is possible that resistance originated from an environmental source, from other species where those antimicrobial agents are used, or transferred from other intestinal bacteria. This study confirms that commercial cattle can carry epidemiologically relevant C. difficile strains at the time of harvest, but the prevalence at the time they enter the food chain is low.     

Control of the bacteriological condition of calf brain. I. Impact of improving hygiene

Sixty calves of the Dutch Friesian (FH) breed were stunned mechanically. Without previously having been stunned, another 30 calves were stuck according to the Jewish rite. Upon opening of the skulls (1–2 h post mortem) brains of mechanically stunned calves were collected either conventionally (n = 30) or ‘hygienically’ (n = 30), i.e. using a fresh pair of surgical gloves during each removal to avoid cross contamination. For ritually slaughtered animals only the hygienic procedure was followed. Samples of 10 g were excised from undamaged hemispheres and in the mechanically stunned treatment group also from the site of impact of the captive bolt. After storage in polystyrene trays at 3 ± 1°C for 7 days sampling was repeated. Bacteriological examination included the assessment of aerobic colony counts at 30°C for 3 days (ACC-30) and 4°C for 14 days (ACC-4) and Enterobacteriaceae colony counts at 37°C for 20 h (ECC). In conventionally collected samples the ACC-30 and ACC-4 were 3.8 and 3.0 log₁₀ cfu g^?1 at day 1 and 6.2 and 6.4 log₁₀ cfu g^?1 at day 8. With hygienic collection these counts were reduced by approximately 1 log unit. Whilst by conventional practice the ECCs, at day 1 and 8 were 2.6 and 4.8 log₁₀ cfu g^?1 these counts were 1.8 and 2.6 log₁₀ cfu g^?1 for hygienic practice. In samples excised from the site of impact of the captive bolt the hygienic procedure had similar, though less marked effects. On day 1 brains from ritually slaughtered animals had a bacteriological contamination similar to that found in the hemispheres of mechanically stunned calves. However, whilst at day 8 their mean ECCs were 3.4 and 3.5 log₁₀ cfu g^?1 the percentages of plates ‘positive’ for Enterobacteriaceae were only 10% in the ritually vs. 53% in the mechanically stunned group. The Enterobacteriaceae in this case were composed of psychrotrophic non-pathogenic genera of environmental origin. Salmonella was not isolated from any sample.     

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.     

The efficacy of pulsed ultrahigh current for the stunning of cattle prior to slaughter

We present results from the development of a new system of reversible electrical stunning of cattle. A single-pulse ultra-high current (SPUC) was generated from a capacitance discharge current spike of at least 5000 V at 70 A, for approximately 50 ms. Ninety-seven cattle were stunned in three experimental protocols. With improvements made to the design of the stun box and charge delivered, 38 cattle were either stunned and immediately jugulated or monitored for signs of reappearance of brain stem reflexes at which point a concussion stun was administered. This use of the SPUC charge, provided as a biphasic-pulse waveform, resulted in a high level of stunning efficacy, with unconsciousness lasting for up to 4 min. These results were supported by EEG data taken from a subsequent cohort of stunned cattle. The SPUC stun also apparently eliminated post-stun grand mal seizures that can occur following short-acting conventional electrical stun, with its associated negative consequences on operator safety and meat quality.     

Impact of transportation and lairage on hide contamination with Escherichia coli O157 in finished beef cattle

Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157. A study was initiated to investigate the influence of transportation and lairage on shedding and hide contamination of E. coli O157. Fecal and hide samples were obtained from 40 pens of harvest-ready beef cattle at the feedlot prior to transport and again at the slaughter plant immediately after slaughter. Potential risk factors for hide contamination at the feedlot, during transport, and at slaughter were evaluated. A multilevel Poisson regression model was used to evaluate if transportation and lairage were associated with hide contamination by E. coli O157 in finished beef cattle. Lots of cattle held in E. coli O157-positive lairage pens had eight times greater risk of having positive slaughter hide samples compared with cattle held in culture-negative pens (relative risk, 8.0; 95% confidence interval, 1.6 to 38.8). Lots of cattle that were held in lairage pens contaminated with feces had three times greater risk for positive slaughter hide samples compared with cattle held in clean pens (relative risk, 3.1; 95% confidence interval, 1.2 to 7.9). Lots of cattle that were transported for long distances (> 160.9 km) had twice the risk of having positive hide samples at slaughter compared with cattle transported a shorter distance (relative risk, 2.4; 95% confidence interval, 1.1 to 5.1). These findings suggest that transportation and lairage should be considered in E. coli O157 control strategies.     

Prevalence of ballooning of the severed carotid arteries at slaughter in cattle, calves and sheep

Previous work in calves indicated that ballooning of the severed arteries is a potential concern in animals receiving a reversible stun before slaughter, and in animals not stunned before slaughter, as it could extend the duration of brain function before the animals die. This study determined the prevalence of ballooning of the carotid arteries in a total of 987 cattle, calves and lambs at slaughter. The severed ends of the carotid arteries were examined by palpation. The prevalence of ballooning that was 3 cm or more in diameter, was 16%, 25% and 0% for cattle, calves and lambs, respectively. Artery sections were taken from a sample of large cattle and examined histologically. In ballooned arteries there was coagulated blood between the outer surface of the artery and the inner aspect of the connective tissue sheath surrounding the artery, suggesting the formation of a false aneurysm in the ballooning phenomenon.     

Prevalence of ballooning of the severed carotid arteries at slaughter in cattle,calves and sheep

Previous work in calves indicated that ballooning of the severed arteries is a potential concern in animals receiving a reversible stun before slaughter, and in animals not stunned before slaughter, as it could extend the duration of brain function before the animals die. This study determined the prevalence of ballooning of the carotid arteries in a total of 987 cattle, calves and lambs at slaughter. The severed ends of the carotid arteries were examined by palpation. The prevalence of ballooning that was 3 cm or more in diameter, was 16%, 25% and 0% for cattle, calves and lambs, respectively. Artery sections were taken from a sample of large cattle and examined histologically. In ballooned arteries there was coagulated blood between the outer surface of the artery and the inner aspect of the connective tissue sheath surrounding the artery, suggesting the formation of a false aneurysm in the ballooning phenomenon.