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The effect of current frequency during waterbath stunning on the physical recovery and rate and extent of bleed out in turkeys
The Effect of Current Frequency During Waterbath Stunning on the Physical Recovery and Rate and Extent of Bleed Out in Turkeys1 M. MOUCHONIE`RE,* G. LE POTTIER,† and X. FERNANDEZ*,2 *INRA—Meat Research Centre, Theix, F-63122 Saint-Gene`s Champanelle, France, and †CIDEF, 11, rue Plaisance, 35310 Mordelles, France
(Key words: turkey, electrical stunning, current frequency, physical recovery, bleeding) 1999 Poultry Science 77:485–489
carcass blemishes (Veerkamp, 1988; Gregory and Wilkins, 1989b). The incidence of cardiac arrest can be reduced at stunning by increasing the frequency of the applied current, with the objective of improved carcass quality. However, the effect of the frequency at 150 mA alternating current on stunning efficiency in turkeys has not been demonstrated. Therefore, the present experiment was designed to investigate the influence of stunning current frequency on the time to physical recovery. In addition, because the incidence of cardiac arrest during stunning may influence the effectiveness of bleeding, a second experiment was undertaken to assess the influence of current frequency on the kinetics of bleeding.
INTRODUCTION In France, all turkey processing plants use electrical waterbath stunners. A recent survey of five French turkey processors showed that electrical stunning conditions vary in terms of waveform and frequency of the current, as well as amperage (Mouchonie`re et al., 1997). Previous studies have shown that the minimum current required to induce a satisfactory stun is 150 mA per turkey and when a sinusoidal 50 Hz alternating current is used to deliver this amount of current, it results in a high incidence of ventricular fibrillation at stunning (Gregory and Wilkins, 1989a). Studies on the effect of stunning current on carcass downgrading in broilers showed that induction of a ventricular fibrillation at stunning is associated with a higher incidence of
MATERIALS AND METHODS
Animal and Stunning Procedure
Received for publication May 16, 1998. Accepted for publication October 30, 1998. 1This study is part of a project financed by Comite ´ Interprofessionnel de la Dinde Franc¸aise (CIDEF), Office Interprofessionnel de la Viande et de l’Aviculture (OFIVAL) and Institut National de la Recherche Agronomique (INRA). 2To whom correspondence should be addressed: fernandz@ clermont.inra.fr
Overall, 122 hens (12 wk old, 5 to 7 kg live weight) and 131 toms (14 wk old, 8 to 9 kg live weight) from the BUT 9 line were subjected to waterbath stunning with an alternating current of various frequencies. These weights correspond to the commercial slaughter weights in France 485
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
Hz was significantly longer than recovery at the four other frequencies. In the second experiment, 50 hens and 53 toms were bled out by a unilateral neck cut 10 s after stunning with one of four different frequencies (50, 300, 480, and 600 Hz). The rate and extent of blood loss within 3 min, relative to live weight, increased as stunning frequency increased. Large differences in the rate and extent of blood loss were observed between turkeys stunned at 50 or 300 Hz, according to the occurrence of cardiac arrest: cardiac activity was associated with significantly higher rate and extent of blood loss in both sexes. Overall, the results suggest that the duration of unconsciousness decreases as stunning frequency increases.
ABSTRACT Two experiments were carried out to evaluate the influence of the frequency of a sinusoidal stunning current (150 mA, 4 s) on the physical recovery of turkey hens and toms and on the rate and extent of blood loss. In the first experiment, physical recovery of 72 hens and 78 toms was estimated after stunning with one of five different frequencies. The incidence of cardiac arrest after stunning at 50, 300, 480, 550, and 600 Hz was, respectively, 100, 60, 30, 30, and 0% in hens and 53, 38, 0, 0, and 0% in toms. In hens, time to return of corneal reflex and neck tension and the onset of wing flapping decreased as frequency increased. In contrast to hens, about half of the toms stunned at 50 Hz did not show cardiac arrest. In these animals, recovery after 50
486
MOUCHONIE`RE ET AL.
according to sex. After an overnight period without feed, turkeys were suspended individually from shackles, the head and upper neck were plunged into a waterbath, and an isolated constant current (150 mA) was applied for 4 s between the water and the shackle. The constant current stunner used in the present study was designed and provided by the Silsoe Research Institute.3
Experimental Design
3Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, U.K.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
Physical Recovery Experiment. Seventy-two hens and 78 toms were assigned to one of five frequency groups and stunned at either 50, 300, 480, 550, or 600 Hz (Table 1). During the stun, voltage has been recorded and impedance was calculated (Table 1). During the 3 min following stunning, the incidence of cardiac arrest, which was recognized from the drooping wings and using stethoscope, or the onset and duration of wing flapping and the time to return of corneal reflex were noted. The term of cardiac arrest should be understood as an irreversible heart dysfunction (fibrillation), leading to undetectable activity with a stethoscope. In every case in which drooping wings and lack of detectable cardiac activity were observed, no recovery occurred and the birds died within a short period. As soon as corneal reflex occurred (return of the nictitating membrane reflex), the bird was removed from the shackles and put on its side on the floor. While in this position, the head was repeatedly raised by the manipulator, once every 5 s, and this was continued until the maintenance of neck posture returned and the bird could hold its head itself. This time was noted as time to return of neck tension. Bleeding Experiment. Fifty hens and 53 toms were weighed and assigned to one of four electrical current frequency groups at either 50, 300, 480, or 600 Hz and stunned (Table 2). Death after stunning was monitored as a cardiac arrest occurring during the first 20 s, i.e., within the first 10 s after neck cutting. Ten seconds after the end of the stun, the birds were bled out by unilateral neck cutting with a hand-held knife which severed one jugular and one carotid. The blood was collected in a graduated test tube and the volume was noted every 20 s during 3 min. Blood loss was expressed as percentage of live weight, based on a density of 1.04 (Kotula and Helbacka, 1966). Statistical Analysis. Analyses of variance were performed using the GLM procedure of SAS (SAS Institute, 1989), to test the influence of current frequency on the various items. When a significant effect was noted, means were compared using Duncan’s multiple range test.
487
TURKEY ELECTRICAL STUNNING TABLE 2. Live weight of turkeys stunned for the bleeding test (x ± SEM) 50 Hz
300 Hz
Hens n = 12
Toms n = 14
Hens n = 14
Toms n = 15
6.7 ± 0.3
9.1 ± 0.4
6.7 ± 0.3
8.6 ± 0.2
RESULTS AND DISCUSSION
Physical Recovery Experiment
FIGURE 1. Rate of cardiac arrest after electrical stunning at 150 mA with various frequencies. 1, 2, or 3 = 0% cardiac arrest after 480, 550, and 600 H2, respectively.
Hens n = 12 (kg) 6.7 ± 0.3
600 Hz
Toms n = 13
Hens n = 12
Toms n = 11
8.7 ± 0.2
6.9 ± 0.2
8.9 ± 0.2
heart. Therefore the greater the volume of skeletal muscle, the greater proportion of current that would go through the external muscles rather than through the internal part of the carcass, where the heart is situated. Regardless of sex, increasing stunning frequency results in a decrease in the time to onset of wing flapping, return of corneal reflex, and return of neck tension (Figure 2). However, in toms, when data obtained at 50 Hz are excluded from the analysis, a significant decrease in the time to return of neck tension is observed with increasing stunning frequency from 300 to 600 Hz (not shown). The duration of wing flapping was not influenced by the frequency of stunning current (mean duration of 10 and 5.5 s, respectively, in hens and toms; data not shown). As far as physical recovery criteria may be considered as indicators of the time to recovery of consciousness following electrical stunning, the present results suggest that increasing the frequency of stunning current decreases the time to recovery. To our knowledge, the present results are the first to report the influence of stunning at varying frequency but constant current on
FIGURE 2. Physical recovery after electrical stunning at 150 mA with various frequencies. Different letters indicate a significant difference between frequencies.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
As shown in Figure 1, 100% of the hens were killed by a 50 Hz stun, whereas 47% of toms showed sustained cardiac activity over the 3-min period. In hens, the incidence of cardiac arrest after a 300 Hz stun (60%) was higher than the corresponding one in toms (40%). Above 300 Hz, all the toms showed sustained cardiac activity, whereas in hens, the minimum frequency for which no cardiac arrest was observed is 600 Hz. Gregory and Wilkins (1989) found 97% of fibrillated heart in turkey hens stunned at 50 Hz with a sinusoidal AC of 150 mA. In broiler, stunning at 1,500 Hz, regardless of amperage, failed to induce any heart fibrillation (Gregory and Wotton, 1991). This latter result is in accordance with the results of the present study, showing that increased frequencies are associated with a lower incidence of cardiac arrest at stunning in turkeys. The difference in percentage of cardiac arrest between hens and toms at given frequencies could be explained by a difference in skeletal muscle mass per volume. Although muscle mass was not measured in this experiment, data exist on the carcass composition of this type of bird: muscle mass is approximately 4.9 kg in 14-wk-old toms and 2.9 kg in 12-wk-old hens, whereas no noticeable difference exists in fat content (British United Turkeys, 1996). Skeletal muscles have a low resistance and are situated around the
480 Hz
488
MOUCHONIE`RE ET AL.
physical recovery of turkeys. A more objective evaluation of the duration of unconsciousness induced by electronarcosis can be obtained with electroencephalogram and somatosensory evoked response recordings. The effect of frequency stunning on electroencephalogram and somatosensory evoked response is being investigated in our laboratory.
Bleeding Experiment Significant effects of current frequency on the rate and extent of bleed out within 3 min following neck cutting were observed in both sexes (Figure 3). In hens, a significantly higher rate and extent of blood loss were recorded after stunning at 480 and 600 Hz than at 50 and 300 Hz. In toms, significantly lower rate and extent of blood loss were observed after stunning at 50 Hz than at other frequencies. The slower rate and extent of blood loss observed at low frequencies (50 or 300 Hz) are most likely due to the corresponding high incidence of cardiac arrest. An illustration of this effect is shown in Figure 4, in which the rate of blood loss is plotted for toms stunned at 50 Hz according to the occurrence of cardiac arrest within the 10 s following stunning. Similar trends were obtained at 300 Hz and for both sexes. Overall, the results show that where stunning does not induce cardiac arrest, the maximum blood is obtained after 2 min, whereas for dead animals, 90% of blood loss is obtained within this period. The maximum difference in rate of blood loss as a result of inducing a cardiac arrest was most evident during the first 40 s of bleeding. The present results are not in accordance with those from Raj et al. (1994), who found no clear relationship between cardiac function and rate of blood loss in turkeys; however, in that study, the comparison was made
between turkeys that showed fibullation or not, after gas stunning. The cardiac activity recorded in unfibrillated birds was, according to the authors, a dysrhythmic activity that may result in cardiac arrest after several minutes. In our experiment, however, the birds that were still alive after electrical stunning were able to fully recover, suggesting that effective cardiac activity was not drastically impaired during the stun. In broilers, however, Raj and Johnson (1997) observed a higher bleeding efficiency after ventral neck cutting following stunning at 1,500 Hz, which does not induce cardiac arrest, compared to stunning at 50 Hz. Overall, the present work shows that increasing the frequency of a 150 mA (sinusoidal alternating current) waterbath stunning decreases the incidence of cardiac arrest and subsequently increases the rate and extent of blood loss after unilateral neck cutting. Physical recovery
FIGURE 4. Influence of cardiac function on the bleeding of toms after a stun at 50 Hz (150 mA). An asterisk indicates a significant difference between dead and live turkeys.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
FIGURE 3. Effect of the current frequency on blood loss rate. For hens, an asterisk indicates significant differences between 50 and 300 Hz vs 480 and 600 Hz. For toms, an asterisk indicates a significant difference between 50 Hz vs 300, 480, and 600 Hz.
TURKEY ELECTRICAL STUNNING
data, however, suggest that the duration of loss of consciousness decreases as stunning frequency increases.
REFERENCES British United Turkey, 1996. BUT9—Performance Goals, Edition 1996/2, British United Turkeys Ltd., Chester, U.K. Gregory, N. G., and L. J. Wilkins, 1989a. Effect of stunning current on downgrading in Turkeys. Br. Poult. Sci. 30: 761–764. Gregory, N. G., and L. J. Wilkins, 1989b. Effect of ventricular fibrillation at stunning and ineffective bleeding on carcass quality defects in broiler chickens. Br. Poult. Sci. 30:825–829. Gregory, N. G., and S. B. Wotton, 1991. Effect of electrical stunning on somatosensory evoked responses in the turkey’s brain. Br. Vet. J. 147:270–273.
489
Kotula, A. W., and N. V. Helbacka, 1966. Blood retained by chicken carcasses and cut up parts as influenced by slaughter method. Poultry Sci. 45:404–410. Mouchonie`re, M., V. Sante´, P. Sale´, P. and G. Le Pottier, 1997. Survey of electrical stunning in some French turkey plants. Turkey 45:19–20. Raj, M., N. G. Gregory, and S. B. Wotton, 1994. Effect of the method of stunning and the interval between stunning and neck cutting on blood loss in turkeys. Vet. Rec. 135:256–258. Raj, M., and S. P. Johnson, 1997. Effect of the method of killing, interval between killing and neck cutting and blood vessels cut on blood loss in broilers. Br. Poult. Sci. 30:190–194. SAS Institute, 1989. SAS/STAT User’s Guide. Release 6.03. SAS Institute Inc., Cary, NC. Veerkamp, C. H., 1988. What is the right current to stun and kill broilers. Poultry 4(4):30–31. Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
(Key words: turkey, electrical stunning, current frequency, physical recovery, bleeding) 1999 Poultry Science 77:485–489
carcass blemishes (Veerkamp, 1988; Gregory and Wilkins, 1989b). The incidence of cardiac arrest can be reduced at stunning by increasing the frequency of the applied current, with the objective of improved carcass quality. However, the effect of the frequency at 150 mA alternating current on stunning efficiency in turkeys has not been demonstrated. Therefore, the present experiment was designed to investigate the influence of stunning current frequency on the time to physical recovery. In addition, because the incidence of cardiac arrest during stunning may influence the effectiveness of bleeding, a second experiment was undertaken to assess the influence of current frequency on the kinetics of bleeding.
INTRODUCTION In France, all turkey processing plants use electrical waterbath stunners. A recent survey of five French turkey processors showed that electrical stunning conditions vary in terms of waveform and frequency of the current, as well as amperage (Mouchonie`re et al., 1997). Previous studies have shown that the minimum current required to induce a satisfactory stun is 150 mA per turkey and when a sinusoidal 50 Hz alternating current is used to deliver this amount of current, it results in a high incidence of ventricular fibrillation at stunning (Gregory and Wilkins, 1989a). Studies on the effect of stunning current on carcass downgrading in broilers showed that induction of a ventricular fibrillation at stunning is associated with a higher incidence of
MATERIALS AND METHODS
Animal and Stunning Procedure
Received for publication May 16, 1998. Accepted for publication October 30, 1998. 1This study is part of a project financed by Comite ´ Interprofessionnel de la Dinde Franc¸aise (CIDEF), Office Interprofessionnel de la Viande et de l’Aviculture (OFIVAL) and Institut National de la Recherche Agronomique (INRA). 2To whom correspondence should be addressed: fernandz@ clermont.inra.fr
Overall, 122 hens (12 wk old, 5 to 7 kg live weight) and 131 toms (14 wk old, 8 to 9 kg live weight) from the BUT 9 line were subjected to waterbath stunning with an alternating current of various frequencies. These weights correspond to the commercial slaughter weights in France 485
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
Hz was significantly longer than recovery at the four other frequencies. In the second experiment, 50 hens and 53 toms were bled out by a unilateral neck cut 10 s after stunning with one of four different frequencies (50, 300, 480, and 600 Hz). The rate and extent of blood loss within 3 min, relative to live weight, increased as stunning frequency increased. Large differences in the rate and extent of blood loss were observed between turkeys stunned at 50 or 300 Hz, according to the occurrence of cardiac arrest: cardiac activity was associated with significantly higher rate and extent of blood loss in both sexes. Overall, the results suggest that the duration of unconsciousness decreases as stunning frequency increases.
ABSTRACT Two experiments were carried out to evaluate the influence of the frequency of a sinusoidal stunning current (150 mA, 4 s) on the physical recovery of turkey hens and toms and on the rate and extent of blood loss. In the first experiment, physical recovery of 72 hens and 78 toms was estimated after stunning with one of five different frequencies. The incidence of cardiac arrest after stunning at 50, 300, 480, 550, and 600 Hz was, respectively, 100, 60, 30, 30, and 0% in hens and 53, 38, 0, 0, and 0% in toms. In hens, time to return of corneal reflex and neck tension and the onset of wing flapping decreased as frequency increased. In contrast to hens, about half of the toms stunned at 50 Hz did not show cardiac arrest. In these animals, recovery after 50
486
MOUCHONIE`RE ET AL.
according to sex. After an overnight period without feed, turkeys were suspended individually from shackles, the head and upper neck were plunged into a waterbath, and an isolated constant current (150 mA) was applied for 4 s between the water and the shackle. The constant current stunner used in the present study was designed and provided by the Silsoe Research Institute.3
Experimental Design
3Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, U.K.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
Physical Recovery Experiment. Seventy-two hens and 78 toms were assigned to one of five frequency groups and stunned at either 50, 300, 480, 550, or 600 Hz (Table 1). During the stun, voltage has been recorded and impedance was calculated (Table 1). During the 3 min following stunning, the incidence of cardiac arrest, which was recognized from the drooping wings and using stethoscope, or the onset and duration of wing flapping and the time to return of corneal reflex were noted. The term of cardiac arrest should be understood as an irreversible heart dysfunction (fibrillation), leading to undetectable activity with a stethoscope. In every case in which drooping wings and lack of detectable cardiac activity were observed, no recovery occurred and the birds died within a short period. As soon as corneal reflex occurred (return of the nictitating membrane reflex), the bird was removed from the shackles and put on its side on the floor. While in this position, the head was repeatedly raised by the manipulator, once every 5 s, and this was continued until the maintenance of neck posture returned and the bird could hold its head itself. This time was noted as time to return of neck tension. Bleeding Experiment. Fifty hens and 53 toms were weighed and assigned to one of four electrical current frequency groups at either 50, 300, 480, or 600 Hz and stunned (Table 2). Death after stunning was monitored as a cardiac arrest occurring during the first 20 s, i.e., within the first 10 s after neck cutting. Ten seconds after the end of the stun, the birds were bled out by unilateral neck cutting with a hand-held knife which severed one jugular and one carotid. The blood was collected in a graduated test tube and the volume was noted every 20 s during 3 min. Blood loss was expressed as percentage of live weight, based on a density of 1.04 (Kotula and Helbacka, 1966). Statistical Analysis. Analyses of variance were performed using the GLM procedure of SAS (SAS Institute, 1989), to test the influence of current frequency on the various items. When a significant effect was noted, means were compared using Duncan’s multiple range test.
487
TURKEY ELECTRICAL STUNNING TABLE 2. Live weight of turkeys stunned for the bleeding test (x ± SEM) 50 Hz
300 Hz
Hens n = 12
Toms n = 14
Hens n = 14
Toms n = 15
6.7 ± 0.3
9.1 ± 0.4
6.7 ± 0.3
8.6 ± 0.2
RESULTS AND DISCUSSION
Physical Recovery Experiment
FIGURE 1. Rate of cardiac arrest after electrical stunning at 150 mA with various frequencies. 1, 2, or 3 = 0% cardiac arrest after 480, 550, and 600 H2, respectively.
Hens n = 12 (kg) 6.7 ± 0.3
600 Hz
Toms n = 13
Hens n = 12
Toms n = 11
8.7 ± 0.2
6.9 ± 0.2
8.9 ± 0.2
heart. Therefore the greater the volume of skeletal muscle, the greater proportion of current that would go through the external muscles rather than through the internal part of the carcass, where the heart is situated. Regardless of sex, increasing stunning frequency results in a decrease in the time to onset of wing flapping, return of corneal reflex, and return of neck tension (Figure 2). However, in toms, when data obtained at 50 Hz are excluded from the analysis, a significant decrease in the time to return of neck tension is observed with increasing stunning frequency from 300 to 600 Hz (not shown). The duration of wing flapping was not influenced by the frequency of stunning current (mean duration of 10 and 5.5 s, respectively, in hens and toms; data not shown). As far as physical recovery criteria may be considered as indicators of the time to recovery of consciousness following electrical stunning, the present results suggest that increasing the frequency of stunning current decreases the time to recovery. To our knowledge, the present results are the first to report the influence of stunning at varying frequency but constant current on
FIGURE 2. Physical recovery after electrical stunning at 150 mA with various frequencies. Different letters indicate a significant difference between frequencies.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
As shown in Figure 1, 100% of the hens were killed by a 50 Hz stun, whereas 47% of toms showed sustained cardiac activity over the 3-min period. In hens, the incidence of cardiac arrest after a 300 Hz stun (60%) was higher than the corresponding one in toms (40%). Above 300 Hz, all the toms showed sustained cardiac activity, whereas in hens, the minimum frequency for which no cardiac arrest was observed is 600 Hz. Gregory and Wilkins (1989) found 97% of fibrillated heart in turkey hens stunned at 50 Hz with a sinusoidal AC of 150 mA. In broiler, stunning at 1,500 Hz, regardless of amperage, failed to induce any heart fibrillation (Gregory and Wotton, 1991). This latter result is in accordance with the results of the present study, showing that increased frequencies are associated with a lower incidence of cardiac arrest at stunning in turkeys. The difference in percentage of cardiac arrest between hens and toms at given frequencies could be explained by a difference in skeletal muscle mass per volume. Although muscle mass was not measured in this experiment, data exist on the carcass composition of this type of bird: muscle mass is approximately 4.9 kg in 14-wk-old toms and 2.9 kg in 12-wk-old hens, whereas no noticeable difference exists in fat content (British United Turkeys, 1996). Skeletal muscles have a low resistance and are situated around the
480 Hz
488
MOUCHONIE`RE ET AL.
physical recovery of turkeys. A more objective evaluation of the duration of unconsciousness induced by electronarcosis can be obtained with electroencephalogram and somatosensory evoked response recordings. The effect of frequency stunning on electroencephalogram and somatosensory evoked response is being investigated in our laboratory.
Bleeding Experiment Significant effects of current frequency on the rate and extent of bleed out within 3 min following neck cutting were observed in both sexes (Figure 3). In hens, a significantly higher rate and extent of blood loss were recorded after stunning at 480 and 600 Hz than at 50 and 300 Hz. In toms, significantly lower rate and extent of blood loss were observed after stunning at 50 Hz than at other frequencies. The slower rate and extent of blood loss observed at low frequencies (50 or 300 Hz) are most likely due to the corresponding high incidence of cardiac arrest. An illustration of this effect is shown in Figure 4, in which the rate of blood loss is plotted for toms stunned at 50 Hz according to the occurrence of cardiac arrest within the 10 s following stunning. Similar trends were obtained at 300 Hz and for both sexes. Overall, the results show that where stunning does not induce cardiac arrest, the maximum blood is obtained after 2 min, whereas for dead animals, 90% of blood loss is obtained within this period. The maximum difference in rate of blood loss as a result of inducing a cardiac arrest was most evident during the first 40 s of bleeding. The present results are not in accordance with those from Raj et al. (1994), who found no clear relationship between cardiac function and rate of blood loss in turkeys; however, in that study, the comparison was made
between turkeys that showed fibullation or not, after gas stunning. The cardiac activity recorded in unfibrillated birds was, according to the authors, a dysrhythmic activity that may result in cardiac arrest after several minutes. In our experiment, however, the birds that were still alive after electrical stunning were able to fully recover, suggesting that effective cardiac activity was not drastically impaired during the stun. In broilers, however, Raj and Johnson (1997) observed a higher bleeding efficiency after ventral neck cutting following stunning at 1,500 Hz, which does not induce cardiac arrest, compared to stunning at 50 Hz. Overall, the present work shows that increasing the frequency of a 150 mA (sinusoidal alternating current) waterbath stunning decreases the incidence of cardiac arrest and subsequently increases the rate and extent of blood loss after unilateral neck cutting. Physical recovery
FIGURE 4. Influence of cardiac function on the bleeding of toms after a stun at 50 Hz (150 mA). An asterisk indicates a significant difference between dead and live turkeys.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015
FIGURE 3. Effect of the current frequency on blood loss rate. For hens, an asterisk indicates significant differences between 50 and 300 Hz vs 480 and 600 Hz. For toms, an asterisk indicates a significant difference between 50 Hz vs 300, 480, and 600 Hz.
TURKEY ELECTRICAL STUNNING
data, however, suggest that the duration of loss of consciousness decreases as stunning frequency increases.
REFERENCES British United Turkey, 1996. BUT9—Performance Goals, Edition 1996/2, British United Turkeys Ltd., Chester, U.K. Gregory, N. G., and L. J. Wilkins, 1989a. Effect of stunning current on downgrading in Turkeys. Br. Poult. Sci. 30: 761–764. Gregory, N. G., and L. J. Wilkins, 1989b. Effect of ventricular fibrillation at stunning and ineffective bleeding on carcass quality defects in broiler chickens. Br. Poult. Sci. 30:825–829. Gregory, N. G., and S. B. Wotton, 1991. Effect of electrical stunning on somatosensory evoked responses in the turkey’s brain. Br. Vet. J. 147:270–273.
489
Kotula, A. W., and N. V. Helbacka, 1966. Blood retained by chicken carcasses and cut up parts as influenced by slaughter method. Poultry Sci. 45:404–410. Mouchonie`re, M., V. Sante´, P. Sale´, P. and G. Le Pottier, 1997. Survey of electrical stunning in some French turkey plants. Turkey 45:19–20. Raj, M., N. G. Gregory, and S. B. Wotton, 1994. Effect of the method of stunning and the interval between stunning and neck cutting on blood loss in turkeys. Vet. Rec. 135:256–258. Raj, M., and S. P. Johnson, 1997. Effect of the method of killing, interval between killing and neck cutting and blood vessels cut on blood loss in broilers. Br. Poult. Sci. 30:190–194. SAS Institute, 1989. SAS/STAT User’s Guide. Release 6.03. SAS Institute Inc., Cary, NC. Veerkamp, C. H., 1988. What is the right current to stun and kill broilers. Poultry 4(4):30–31. Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on March 15, 2015