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False aneurysms in carotid arteries of cattle and water buffalo during shechita and halal slaughter
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MEAT SCIENCE Meat Science 79 (2008) 285–288 www.elsevier.com/locate/meatsci
False aneurysms in carotid arteries of cattle and water buffalo during shechita and halal slaughter Neville G. Gregory
a,*
, Martin von Wenzlawowicz b, Rashedul M. Alam c, Haluk M. Anil d, Tahsin Yesßildere e, Ayona Silva-Fletcher a a BBSRC & Royal Veterinary College, Hatfield AL9 7TA, UK Beratungs- und Schulungsinstitut, Pf 1469, D-21487 Schwarzenbek, Germany Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh d Bristol University, Langford BS40 5DU, UK e Veterinary Association, Hamson Apt. 26/3, Tunel/Beyoglu, Istanbul, Turkey
b c
Received 30 July 2007; received in revised form 25 September 2007; accepted 25 September 2007
Abstract 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. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Cattle; Water buffalo; Religious slaughter; Shechita; Halal; Aneurysms; Carotid artery; Exsanguination; Bleeding; Electrical stunning; Cardiac arrest
1. Introduction Cattle have an unusual anatomical feature in the cephalic blood vessels, which may be important during slaughter for meat consumption. They have basi-occipito plexuses that allow blood to pass to the brain through an alternative route to the branches of the carotid arteries (Baldwin, 1960). Blood supplied through the plexuses delays cerebral hypoxaemia during occlusion of the carotid arteries (Baldwin & Bell, 1963a, 1963b). Cattle are also prone to develop false aneurysms in the common carotid arteries when those *
Corresponding author. E-mail address: [email protected] (N.G. Gregory).
0309-1740/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.09.012
arteries are severed during slaughter following stunning (Gregory, Shaw, Whitford, & Patterson-Kane, 2006). The combination of false aneurysm formation in the carotids plus collateral blood flow through the plexuses presents a theoretical risk of recovery of consciousness during slaughter following reversible stunning methods such as electric currents applied to the head (Anil, McKinstry, Wotton, & Gregory, 1995). The combination also presents a theoretical risk of prolonged periods of consciousness following religious slaughter when there is no preslaughter stunning. The risk of prolonged consciousness would depend on whether carotid false aneurysms form during religious slaughter. The magnitude of this risk is not known in the case of shechita and halal, but it may be small in view of
286
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
the close attention paid to knife condition and the precise way the cut is performed (Levinger, 1976; Khan, 1982). The present study examined whether carotid false aneurysms can and do occur during shechita and halal slaughter performed in cattle and water buffalo. 2. Materials and methods Halal and shechita were observed at a total of six slaughter premises in Europe and Asia. The premises were chosen on the basis that they were known to perform shechita or halal slaughter and they were willing to take part in the study. The slaughter facilities included four abattoirs, one town slaughter slab and one village slaughter slab. At two of the facilities a rotary pen was used for presenting the animal in dorsal recumbency for the cut, at two premises the animals were cast manually using ropes fastened to the legs and then whilst in lateral recumbency the neck was twisted to present the ventral aspect uppermost, at one abattoir the head was restrained whilst the animal was upright and the ventral aspect of the neck was lowermost, and at one abattoir the animals were first hoisted from an upright restraining pen with a shackle secured to a leg and then were cut after they had been lowered and were in lateral recumbency on a shoulder and with the neck twisted. One facility used a rotary pen for shechita as well as halal. Slaughter was examined in a total of 231 cattle killed by shechita and 116 cattle plus 11 water buffalo killed by the halal method. None of the animals were stunned before the cuts were made in the neck by a total of seven and five men of the respective faiths. The animals included yearlings, cull dairy cows, cull draft Haryana cattle and water buffalo, and finished bulls, steers and heifers of European and Asian cattle breeds. The number of cuts made in the neck was recorded for each animal. One cut represented a movement in one direction whilst cutting the soft tissues before a change of direction or withdrawal of the knife. At one abattoir where halal slaughter was observed, cattle not destined for the halal meat trade were electrically stunned whilst they were in the rotary pen, using 2.1 A applied to the head followed by 1.4 A applied between the nose and brisket (Banss GmbH, Germany). In slaughter following captive bolt stunning, false aneurysms can develop when blood flows from the severed ends of the carotid arteries into the surrounding connective tissue sheath. The false aneurysms take the form of encapsulated haematomas and can be distinguished in situ from normal arteries by their swollen size (Gregory et al., 2006). The arteries were located by inserting a hand through the skin wound created by the cut, and following the flow of blood back to the severed end of an artery. The outer diameter of the artery or false aneurysm was assessed by gently palpating the artery with the tips of the fingers and thumb without squeezing the artery. The size of each artery was graded at about 30 s following the cut whilst the animal was bleeding out using the 0 to
6-point scale reported by Gregory et al. (2006), where increasing score corresponds to increasing diameter. When there was doubt about the assessment, the artery was inspected visually and the diameter measured by ruler. Previous experience showed that palpation was a reliable way of assessing the outer diameter of normal arteries and arteries with false aneurysms. The correlation coefficient between estimation of outer diameter by palpation (y) and measurement by ruler (x) was 0.96 (linear regression coefficient = 0.93; Gregory et al., 2006). In some cases, and in particular when there was reduced blood flow, the arteries were located by a combination of palpation and visual inspection. Any arteries that were not cut, or were incompletely cut, were noted. In order to ensure consistency in the comparisons, one person only made all the assessments on the arteries. At three premises the animals were suspended vertically by leg-shackle with the head hanging downwards at 30 s following the cut. Visual inspection was not easy in all those animals during full flow of blood, but it was possible during full flow of blood in animals that were horizontal during the bleeding period. Statistical analyses of the results were by Fisher’s exact test. 3. Results On average, during shechita and halal in cattle, large false aneurysms (outer diameter P3 cm) were formed in 10% of arteries (Table 1). The range in the prevalence between countries in the prevalence of large false aneurysms in cattle was 9–12%. The prevalence of animals with one or two false aneurysms larger than 3 cm outer diameter was 18% and 17% for shechita and halal, respectively. In three animals, in which it was noted that arterial blood flow stopped within 20 s after both carotid arteries had been severed, false aneurysm sizes were 2 cm for one artery and at least 3 cm for the other. Using this as an indicator of risk, 8% of cattle slaughtered by halal and 7% of cattle slaughtered by shechita were in this category. Three out of the 11 water buffalo had comparable bilateral false aneurysms. There were no differences in the prevalence of false aneurysms in arteries according to breed of cattle (Asian versus European), method of restraint (inverted versus lateral versus upright) or slaughter premises (slab versus abattoir) (P > 0.05). The range in prevalence of arteries with false aneurysms (outer diameter P3 cm) for these seven situations was 9–13%. The prevalence of false aneurysms with a diameter of three or more cm was greater in halal-slaughtered water buffalo than halal-slaughtered cattle (Table 1; P < 0.01). Water buffalo presented an additional complication during halal. The breadth of the horns in some water buffalo meant that the neck could not be twisted to present the ventral surface uppermost for the cut whilst in lateral recumbency on the floor. As a result the knife had to be inserted from the side and then worked, using small repetitive cutting actions, ventrally. In this way, up to 19 cuts
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
287
Table 1 Prevalence and size of carotid artery aneurysms following slaughter in stunned and non-stunned cattle and water buffalo Method
Shechita
Halal Halal Stunning without cardiac arresta Stunning with cardiac arrest a
Country
Number of slaughter facilities (slaughter-men)
Turkey, France and UK Bangladesh and France Bangladesh
1 (1)
UK
1 (4)
France
1 (1)
Number of animals
Number of cuts per animal ± se
% carotid arteries according to the size of the severed end, cm diameter 61
2
3
4
5+
% animals with a carotid artery P3 cm
% animals with a carotid artery incompletely cut
% animals with a carotid artery not cut
3 (3)
231 cattle
3.2 ± 0.1
73
12
8
1
<1
18
4
6
2 (7)
116 cattle 11 buffalo 387 cattle
5.2 ± 0.2
72
18
9
1
0
17
0
1
6.9 ± 1.5
54
14
27
5
0
36
0
0
–
62
21
10
4
2
25
<1
1
7.9 ± 1.0
98
0
0
0
0
0
0
5
20 cattle
Data reproduced from Gregory et al. (2006).
were used to sever the soft tissues on the underside of the neck, but on average the water buffalo received seven cuts. All the cattle that had been electrically stunned before the neck was cut had very little blood flowing from the severed arteries, confirming that they had developed a cardiac arrest. None of the carotid arteries in these animals had false aneurysms, which demonstrated that strong arterial pressure was essential for false aneurysm formation. The prevalence of arteries that were two or more cm in diameter following halal slaughter at the same abattoir was 24%, compared with 0% for the cattle that were electrically stunned and developed a cardiac arrest (P < 0.001). There were 21 animals slaughtered by shechita where a carotid artery was incompletely cut or not cut at all. Four of these animals had inadequate cutting in both arteries. The prevalence of failure to cut a carotid artery was higher during shechita than halal slaughter (6% and 1%, respectively, P < 0.05). 4. Discussion It has been noted previously that some cattle take a relatively long time to lose brain activity during shechita. For example, in one study the time to loss of somatosensory evoked cortical responses varied between 32 and 126 s (Daly, Kallweit, & Ellendorf, 1988). At the time that study was conducted, the reason for this variation was unclear. Similarly, slaughter without stunning in cattle held in an upright position has resulted in long delays (up to 135 s) in some animals before physical collapse (Blackmore, 1984). In addition, some cattle have shown a period of recovery, including escape behaviour, following collapse after the shechita cuts (Levinger, 1976). The reason for the variation between individuals has not been explained, but the findings in the present study introduce false aneu-
rysm formation, in combination with the collateral supply of blood to the brain through the basi-occipital plexus, as a potential explanation. False aneurysms form when blood infiltrates into subadventitial layers around the severed arteries. The resulting encapsulated haematoma can range from a uniform concentric layer around the artery to an irregular bulge, which creates tortuosity in the artery. It was clear during this study that continued enlargement of the false aneurysm during the early stages of bleeding can lead to obliteration of the vessel. The reasons why some arteries develop false aneurysms and cease to flow whilst others do not are not clear, but they could relate to the way blood is directed from the severed end of the artery or from ruptured side branches of the artery. The predisposing factors are not understood. This study showed that false aneurysms did not occur following electrical stunning with cardiac arrest. This indicates that the aneurysms do not form when blood pressure is suppressed, and this implies that false aneurysms are more likely to form during the early part of the bleeding period in animals that have a beating heart. There is no reason to suppose that stunning influences false aneurysm development other than through its effect on blood pressure. For example, cattle shot by captive bolt before cutting the vessels in the neck, can develop false aneurysms at the severed ends of the carotids (reproduced from Gregory, Shaw, Whitford, & Patterson-Kane, 2006 in Table 1). The prevalence of false aneurysm formation was 10% of the arteries and 18% of the cattle. The prevalence of failure to cut the carotid arteries during shechita was 6%, which was higher than that given in a previous report (less than 1%; Levinger, 1976). The primary conclusion from this study is that false aneurysms do develop during shechita and halal slaughter.
288
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
This could pose a risk of extended consciousness for some of those animals. Since only a proportion of animals are likely to experience the risk, two approaches could be taken when deciding how this situation should be managed. Firstly, the magnitude of the risk of extended consciousness could be determined and then it could be decided whether the hazard warrants further action. Alternatively, the predisposing factors leading to false aneurysm formation could be identified and then ways of overcoming or preventing false aneurysm formation could be considered, to eliminate the risk altogether. References Anil, M. H., McKinstry, J. L., Wotton, S. B., & Gregory, N. G. (1995). Welfare of calves – 1. Investigations into some aspects of calf slaughter. Meat Science, 41, 101–112. Baldwin, B. A. (1960). The correlation between the vascular supply of the brain and cerebral function in ruminants. Ph.D. thesis, Royal Veterinary College, University of London.
Baldwin, B. A., & Bell, F. R. (1963a). The effect of temporary reduction in cephalic blood flow on the EEG of sheep and cattle. Electroencephalography and clinical Neurophysiology, 15, 465–473. Baldwin, B. A., & Bell, F. R. (1963b). The effect on blood pressure in the sheep and calf of clamping some of the arteries contributing to the cephalic circulation. Journal of Physiology, 167, 448–462. Blackmore, D. K. (1984). Differences in behaviour between sheep and cattle during slaughter. Research in Veterinary Science, 37, 223–226. Daly, C. C., Kallweit, E., & Ellendorf, F. (1988). Cortical function in cattle during slaughter: Conventional captive bolt stunning followed by exsanguinations compared with shechita slaughter. Veterinary Record, 122, 325–329. Gregory, N. G., Shaw, F. D., Whitford, J. C., & Patterson-Kane, J. C. (2006). Prevalence of ballooning of the severed carotid arteries at slaughter in cattle, calves and sheep. Meat Science, 74, 655–657. Khan, G. M. (1982). In Al-dhabh. Slaying animals for food the Islamic way (pp. 62). London: Islamic Medical Association. Levinger, I.M. (1976). Physiological and general medical aspects of shechita. Reprint from: In E. Munk, & M. L. Munk (Eds.). Shechita. Religious, historical and scientific aspects (p. 214). Jerusalem: Gur Aryeh Publications.
MEAT SCIENCE Meat Science 79 (2008) 285–288 www.elsevier.com/locate/meatsci
False aneurysms in carotid arteries of cattle and water buffalo during shechita and halal slaughter Neville G. Gregory
a,*
, Martin von Wenzlawowicz b, Rashedul M. Alam c, Haluk M. Anil d, Tahsin Yesßildere e, Ayona Silva-Fletcher a a BBSRC & Royal Veterinary College, Hatfield AL9 7TA, UK Beratungs- und Schulungsinstitut, Pf 1469, D-21487 Schwarzenbek, Germany Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh d Bristol University, Langford BS40 5DU, UK e Veterinary Association, Hamson Apt. 26/3, Tunel/Beyoglu, Istanbul, Turkey
b c
Received 30 July 2007; received in revised form 25 September 2007; accepted 25 September 2007
Abstract 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. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Cattle; Water buffalo; Religious slaughter; Shechita; Halal; Aneurysms; Carotid artery; Exsanguination; Bleeding; Electrical stunning; Cardiac arrest
1. Introduction Cattle have an unusual anatomical feature in the cephalic blood vessels, which may be important during slaughter for meat consumption. They have basi-occipito plexuses that allow blood to pass to the brain through an alternative route to the branches of the carotid arteries (Baldwin, 1960). Blood supplied through the plexuses delays cerebral hypoxaemia during occlusion of the carotid arteries (Baldwin & Bell, 1963a, 1963b). Cattle are also prone to develop false aneurysms in the common carotid arteries when those *
Corresponding author. E-mail address: [email protected] (N.G. Gregory).
0309-1740/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.09.012
arteries are severed during slaughter following stunning (Gregory, Shaw, Whitford, & Patterson-Kane, 2006). The combination of false aneurysm formation in the carotids plus collateral blood flow through the plexuses presents a theoretical risk of recovery of consciousness during slaughter following reversible stunning methods such as electric currents applied to the head (Anil, McKinstry, Wotton, & Gregory, 1995). The combination also presents a theoretical risk of prolonged periods of consciousness following religious slaughter when there is no preslaughter stunning. The risk of prolonged consciousness would depend on whether carotid false aneurysms form during religious slaughter. The magnitude of this risk is not known in the case of shechita and halal, but it may be small in view of
286
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
the close attention paid to knife condition and the precise way the cut is performed (Levinger, 1976; Khan, 1982). The present study examined whether carotid false aneurysms can and do occur during shechita and halal slaughter performed in cattle and water buffalo. 2. Materials and methods Halal and shechita were observed at a total of six slaughter premises in Europe and Asia. The premises were chosen on the basis that they were known to perform shechita or halal slaughter and they were willing to take part in the study. The slaughter facilities included four abattoirs, one town slaughter slab and one village slaughter slab. At two of the facilities a rotary pen was used for presenting the animal in dorsal recumbency for the cut, at two premises the animals were cast manually using ropes fastened to the legs and then whilst in lateral recumbency the neck was twisted to present the ventral aspect uppermost, at one abattoir the head was restrained whilst the animal was upright and the ventral aspect of the neck was lowermost, and at one abattoir the animals were first hoisted from an upright restraining pen with a shackle secured to a leg and then were cut after they had been lowered and were in lateral recumbency on a shoulder and with the neck twisted. One facility used a rotary pen for shechita as well as halal. Slaughter was examined in a total of 231 cattle killed by shechita and 116 cattle plus 11 water buffalo killed by the halal method. None of the animals were stunned before the cuts were made in the neck by a total of seven and five men of the respective faiths. The animals included yearlings, cull dairy cows, cull draft Haryana cattle and water buffalo, and finished bulls, steers and heifers of European and Asian cattle breeds. The number of cuts made in the neck was recorded for each animal. One cut represented a movement in one direction whilst cutting the soft tissues before a change of direction or withdrawal of the knife. At one abattoir where halal slaughter was observed, cattle not destined for the halal meat trade were electrically stunned whilst they were in the rotary pen, using 2.1 A applied to the head followed by 1.4 A applied between the nose and brisket (Banss GmbH, Germany). In slaughter following captive bolt stunning, false aneurysms can develop when blood flows from the severed ends of the carotid arteries into the surrounding connective tissue sheath. The false aneurysms take the form of encapsulated haematomas and can be distinguished in situ from normal arteries by their swollen size (Gregory et al., 2006). The arteries were located by inserting a hand through the skin wound created by the cut, and following the flow of blood back to the severed end of an artery. The outer diameter of the artery or false aneurysm was assessed by gently palpating the artery with the tips of the fingers and thumb without squeezing the artery. The size of each artery was graded at about 30 s following the cut whilst the animal was bleeding out using the 0 to
6-point scale reported by Gregory et al. (2006), where increasing score corresponds to increasing diameter. When there was doubt about the assessment, the artery was inspected visually and the diameter measured by ruler. Previous experience showed that palpation was a reliable way of assessing the outer diameter of normal arteries and arteries with false aneurysms. The correlation coefficient between estimation of outer diameter by palpation (y) and measurement by ruler (x) was 0.96 (linear regression coefficient = 0.93; Gregory et al., 2006). In some cases, and in particular when there was reduced blood flow, the arteries were located by a combination of palpation and visual inspection. Any arteries that were not cut, or were incompletely cut, were noted. In order to ensure consistency in the comparisons, one person only made all the assessments on the arteries. At three premises the animals were suspended vertically by leg-shackle with the head hanging downwards at 30 s following the cut. Visual inspection was not easy in all those animals during full flow of blood, but it was possible during full flow of blood in animals that were horizontal during the bleeding period. Statistical analyses of the results were by Fisher’s exact test. 3. Results On average, during shechita and halal in cattle, large false aneurysms (outer diameter P3 cm) were formed in 10% of arteries (Table 1). The range in the prevalence between countries in the prevalence of large false aneurysms in cattle was 9–12%. The prevalence of animals with one or two false aneurysms larger than 3 cm outer diameter was 18% and 17% for shechita and halal, respectively. In three animals, in which it was noted that arterial blood flow stopped within 20 s after both carotid arteries had been severed, false aneurysm sizes were 2 cm for one artery and at least 3 cm for the other. Using this as an indicator of risk, 8% of cattle slaughtered by halal and 7% of cattle slaughtered by shechita were in this category. Three out of the 11 water buffalo had comparable bilateral false aneurysms. There were no differences in the prevalence of false aneurysms in arteries according to breed of cattle (Asian versus European), method of restraint (inverted versus lateral versus upright) or slaughter premises (slab versus abattoir) (P > 0.05). The range in prevalence of arteries with false aneurysms (outer diameter P3 cm) for these seven situations was 9–13%. The prevalence of false aneurysms with a diameter of three or more cm was greater in halal-slaughtered water buffalo than halal-slaughtered cattle (Table 1; P < 0.01). Water buffalo presented an additional complication during halal. The breadth of the horns in some water buffalo meant that the neck could not be twisted to present the ventral surface uppermost for the cut whilst in lateral recumbency on the floor. As a result the knife had to be inserted from the side and then worked, using small repetitive cutting actions, ventrally. In this way, up to 19 cuts
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
287
Table 1 Prevalence and size of carotid artery aneurysms following slaughter in stunned and non-stunned cattle and water buffalo Method
Shechita
Halal Halal Stunning without cardiac arresta Stunning with cardiac arrest a
Country
Number of slaughter facilities (slaughter-men)
Turkey, France and UK Bangladesh and France Bangladesh
1 (1)
UK
1 (4)
France
1 (1)
Number of animals
Number of cuts per animal ± se
% carotid arteries according to the size of the severed end, cm diameter 61
2
3
4
5+
% animals with a carotid artery P3 cm
% animals with a carotid artery incompletely cut
% animals with a carotid artery not cut
3 (3)
231 cattle
3.2 ± 0.1
73
12
8
1
<1
18
4
6
2 (7)
116 cattle 11 buffalo 387 cattle
5.2 ± 0.2
72
18
9
1
0
17
0
1
6.9 ± 1.5
54
14
27
5
0
36
0
0
–
62
21
10
4
2
25
<1
1
7.9 ± 1.0
98
0
0
0
0
0
0
5
20 cattle
Data reproduced from Gregory et al. (2006).
were used to sever the soft tissues on the underside of the neck, but on average the water buffalo received seven cuts. All the cattle that had been electrically stunned before the neck was cut had very little blood flowing from the severed arteries, confirming that they had developed a cardiac arrest. None of the carotid arteries in these animals had false aneurysms, which demonstrated that strong arterial pressure was essential for false aneurysm formation. The prevalence of arteries that were two or more cm in diameter following halal slaughter at the same abattoir was 24%, compared with 0% for the cattle that were electrically stunned and developed a cardiac arrest (P < 0.001). There were 21 animals slaughtered by shechita where a carotid artery was incompletely cut or not cut at all. Four of these animals had inadequate cutting in both arteries. The prevalence of failure to cut a carotid artery was higher during shechita than halal slaughter (6% and 1%, respectively, P < 0.05). 4. Discussion It has been noted previously that some cattle take a relatively long time to lose brain activity during shechita. For example, in one study the time to loss of somatosensory evoked cortical responses varied between 32 and 126 s (Daly, Kallweit, & Ellendorf, 1988). At the time that study was conducted, the reason for this variation was unclear. Similarly, slaughter without stunning in cattle held in an upright position has resulted in long delays (up to 135 s) in some animals before physical collapse (Blackmore, 1984). In addition, some cattle have shown a period of recovery, including escape behaviour, following collapse after the shechita cuts (Levinger, 1976). The reason for the variation between individuals has not been explained, but the findings in the present study introduce false aneu-
rysm formation, in combination with the collateral supply of blood to the brain through the basi-occipital plexus, as a potential explanation. False aneurysms form when blood infiltrates into subadventitial layers around the severed arteries. The resulting encapsulated haematoma can range from a uniform concentric layer around the artery to an irregular bulge, which creates tortuosity in the artery. It was clear during this study that continued enlargement of the false aneurysm during the early stages of bleeding can lead to obliteration of the vessel. The reasons why some arteries develop false aneurysms and cease to flow whilst others do not are not clear, but they could relate to the way blood is directed from the severed end of the artery or from ruptured side branches of the artery. The predisposing factors are not understood. This study showed that false aneurysms did not occur following electrical stunning with cardiac arrest. This indicates that the aneurysms do not form when blood pressure is suppressed, and this implies that false aneurysms are more likely to form during the early part of the bleeding period in animals that have a beating heart. There is no reason to suppose that stunning influences false aneurysm development other than through its effect on blood pressure. For example, cattle shot by captive bolt before cutting the vessels in the neck, can develop false aneurysms at the severed ends of the carotids (reproduced from Gregory, Shaw, Whitford, & Patterson-Kane, 2006 in Table 1). The prevalence of false aneurysm formation was 10% of the arteries and 18% of the cattle. The prevalence of failure to cut the carotid arteries during shechita was 6%, which was higher than that given in a previous report (less than 1%; Levinger, 1976). The primary conclusion from this study is that false aneurysms do develop during shechita and halal slaughter.
288
N.G. Gregory et al. / Meat Science 79 (2008) 285–288
This could pose a risk of extended consciousness for some of those animals. Since only a proportion of animals are likely to experience the risk, two approaches could be taken when deciding how this situation should be managed. Firstly, the magnitude of the risk of extended consciousness could be determined and then it could be decided whether the hazard warrants further action. Alternatively, the predisposing factors leading to false aneurysm formation could be identified and then ways of overcoming or preventing false aneurysm formation could be considered, to eliminate the risk altogether. References Anil, M. H., McKinstry, J. L., Wotton, S. B., & Gregory, N. G. (1995). Welfare of calves – 1. Investigations into some aspects of calf slaughter. Meat Science, 41, 101–112. Baldwin, B. A. (1960). The correlation between the vascular supply of the brain and cerebral function in ruminants. Ph.D. thesis, Royal Veterinary College, University of London.
Baldwin, B. A., & Bell, F. R. (1963a). The effect of temporary reduction in cephalic blood flow on the EEG of sheep and cattle. Electroencephalography and clinical Neurophysiology, 15, 465–473. Baldwin, B. A., & Bell, F. R. (1963b). The effect on blood pressure in the sheep and calf of clamping some of the arteries contributing to the cephalic circulation. Journal of Physiology, 167, 448–462. Blackmore, D. K. (1984). Differences in behaviour between sheep and cattle during slaughter. Research in Veterinary Science, 37, 223–226. Daly, C. C., Kallweit, E., & Ellendorf, F. (1988). Cortical function in cattle during slaughter: Conventional captive bolt stunning followed by exsanguinations compared with shechita slaughter. Veterinary Record, 122, 325–329. Gregory, N. G., Shaw, F. D., Whitford, J. C., & Patterson-Kane, J. C. (2006). Prevalence of ballooning of the severed carotid arteries at slaughter in cattle, calves and sheep. Meat Science, 74, 655–657. Khan, G. M. (1982). In Al-dhabh. Slaying animals for food the Islamic way (pp. 62). London: Islamic Medical Association. Levinger, I.M. (1976). Physiological and general medical aspects of shechita. Reprint from: In E. Munk, & M. L. Munk (Eds.). Shechita. Religious, historical and scientific aspects (p. 214). Jerusalem: Gur Aryeh Publications.