Effect of the method of killing,interval between killing and neck cutting and blood vessels cut on blood loss in broilers

1. Broiler chickens were killed using 90% argon in air, or 30% carbon dioxide and 60% argon in air or 120 mA per bird in a waterbath with a 50 Hz alternating electric current. Ventral or unilateral neck cutting was performed at 1, 3 or 5 min after killing. In addition, a group of broilers was stunned with 120 mA per bird in a waterbath using 1500 Hz alternating current and were bled out with a ventral neck cut within 20 s from stunning.

2. Blood leaving the neck wound was collected in a bin placed on an electronic balance and a computer program calculated the cumulative blood loss up to 100 s after neck cutting.

3. Bleed‐out was significantly affected by killing method and time of neck cutting. Broilers killed with the carbon dioxide‐argon mixture bled‐out less than those killed with argon or 50 Hz electric current. When compared with the 1 min neck cutting interval, a delay of 3 or 5 min resulted in a lower bleed‐out. High frequency electrical stunning and ventral neck cutting within 20 s resulted in a slightly higher bleed‐out than those recorded for the killing methods. However, within argon killing, a delay of 3 or 5 min in ventral or unilateral neck cutting had no significant effect on the bleed‐out. In broilers killed with the carbon dioxide‐argon mixture a 3 min delay in ventral neck cutting or a 5 min delay in unilateral neck cutting resulted in lower bleed‐out.

4. Neck cutting of broilers within 5 min after argon killing or 3 min after killing with the carbon dioxide‐argon mixture would result in a satisfactory bleed‐out.     

Effect of electrical stunning on somatosensory evoked responses in the turkey's brain

The effects of head only or waterbath electrical stunning on somatosensory evoked responses in the brain of turkeys were examined. When head only stunning with a sinusoidal AC of 50 Hz was followed within 15 s by neck cutting the evoked responses were absent following the stun. When neck cutting was not performed, the evoked responses returned from 30 s after the stun. When currents between 120 and 250 mA were used in a waterbath stunner some birds retained their evoked responses immediately after the current was applied. The proportion of birds that retained their responses after the stun was not related to the level of the current that was applied.     

Carcase and meat quality in ducks killed with either gas mixtures or an electric current under commercial processing conditions

1. The feasibility of killing 7-week old Peking ducks with gas mixtures and their effects on carcase and meat quality were evaluated and compared with killing in electrical waterbath under commercial conditions. 2. The prevalence of carcase appearance defects and broken bones in the carcases and haemorrhaging, pH, colour, cooking loss and texture of breast muscles were determined. 3. Ducks can be killed within 3 min by exposure to either 90% argon in air or a mixture of 30% carbon dioxide and 60% argon in air. 4. Gas or controlled-atmosphere killing of ducks, whilst they are still in their transport containers, would eliminate some of the welfare concerns associated with the conventional electrical waterbath stunning systems, without adversely affecting carcase and meat quality.     

Broken bones in domestic fowl: handling and processing damage in end-of-lay battery hens

1. 3115 end-of-lay battery hens and carcases were sampled at set points in the sequence of events that occurred between depopulation of the battery cages at the layer farms and the end of the evisceration line in two processing plants. Live birds were killed in a convulsion-free manner and carcases were dissected to determine the incidence of broken bones. 2. Of the live battery birds 29% had broken bones by the time they reached the waterbath stunner, with on average 0.5 broken bones per bird. Removing birds from the battery cages and hanging them on the slaughter line were identified as causes of broken bones. 3. By the time birds left the end of the eviscerating line, 98% of carcases had broken bones, with on average 6 broken bones each. The stunning, plucking and eviscerating processes caused most of this damage. In particular, stunning broke the furculum, coracoid and scapula, plucking broke the ischium, pubis and ribs, and evisceration damaged the ischium and pubis.     

Broiler carcass quality using head-only electrical stunning in a waterbath

1. The objective was to assess carcass quality of broilers when they were stunned by immersing their heads in a waterbath with an electric current flowing from one side of it to the other, while a second small current passed through the body to the waterbath to prevent involuntary wing flapping. 2. The prevalence of wing, shoulder and breast fillet haemorrhages and of broken bones in the pectoral region was not greater than that resulting from the normal stunning practice in that plant (63 mA, 610 Hz pDC). 3. These results imply that carcass damage using this technique will be significantly lower than that which will result from the application of higher stunning currents required by the new EU slaughter poultry slaughter regulations.     

Head-cloaca controlled current stunning: assessment of brain and heart activity and meat quality

1. Behavioural and neural responses of 65 broilers to head-to-cloaca electrical stunning were evaluated and meat quality was assessed on two groups of 25 broilers stunned either head to cloaca, or in a conventional water bath method.

2. On the EEG recordings, a general epileptiform insult was observed when applying a current of 100?mA (100?Hz) or 70?mA (70?Hz) for 1·5?s. This general epileptiform insult shows a tonic, clonic and exhaustion phase followed by spikes of alpha, beta, theta and delta waves with duration of on average 34?±?12?s and 39?±?23?s respectively. These birds may have been unconscious for 20?s or longer, according to the correlation dimension analyses.

3. The heart rate decreased significantly (P? 4. Within a confidence limit of 95%, taking into account the number of animals with a reliable EEG, the chance of an effective stun of all broilers lies between 0·9 and 1·0?with a current of 70?mA (100?Hz for 1·5?s; n?=?28) and with 100?mA (100?Hz for 1·5?s; n?=?27).

5. The shear force of breast fillets was slightly lower (P? 6. It can be concluded that broilers are effectively stunned with the head-cloaca method by using a controlled current of 70?mA or 100?mA for 1·5?s. The fillets and legs of bird stunned head-cloaca showed fewer blood splashes in the muscles compared with birds stunned in a conventional water bath.     

Survival rate and carcase downgrading after the stunning of broilers with carbon dioxide-argon mixtures.

As chickens may rapidly regain consciousness after gas stunning, the effects of a two minute exposure to a carbon dioxide-argon mixture on survival rate were investigated. Broilers were stunned in batches of 10 per transport crate with a mixture of 10, 20 or 30 per cent carbon dioxide in argon with 5 per cent residual oxygen. The birds were exposed to the gaseous atmosphere for two minutes. A control group of birds was electrically stunned (120 mA for four seconds; 50Hz sinusoidal waveform). In addition, the incidence of carcase downgrading conditions after stunning with 20 per cent or 30 per cent carbon dioxide in argon with 5 per cent residual oxygen was compared with the incidence after electrical stunning. The results showed that stunning with 10 and 20 per cent carbon dioxide in argon with 5 per cent residual oxygen resulted in survival rates of 24 and 1 per cent, respectively. Stunning with 30 per cent carbon dioxide in argon with 5 per cent residual oxygen resulted in the death of all the broilers. Electrical stunning resulted in a significantly (P less than 0.001) larger number of broilers with breast muscle haemorrhaging and broken furculum and coracoid bones, whereas stunning with gas mixtures resulted in a significantly (P less than 0.001) higher incidence of broilers with damaged wing bones. Electrical stunning of broilers resulted in a significantly higher pH in the breast muscles 20 minutes post mortem than stunning with carbon dioxide-argon mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Head-only electrical stunning of poultry using a waterbath: a feasibility study

1. The objective of this work was to investigate the feasibility of head only waterbath stunning as a means of generating immediate and long lasting unconsciousness while preventing wing flapping and avoiding carcass damage. 2. EEG measurements showed that immersion of the heads of the broilers for one second in a waterbath containing water of conductivity 2 x 5 mS/cm and a 50 Hz electric field of 10 V/cm resulted in immediate unconsciousness, and that increasing the electric field strength extended the duration of unconsciousness. 3. The passage of a 25-30 mA alternating current of frequency 2000 Hz through the broilers' bodies suppressed the wing flapping that followed a stun. 4. When the body current and electric field were applied simultaneously, wing flapping was prevented and EEG signals were suppressed for over 30 seconds indicating that the immediate unconsciousness lasted long enough to facilitate humane slaughter.     

Electrocorticogram spectral analysis and somatosensory evoked potentials as tools to assess electrical stunning efficiency in ducks

1. Fast Fourier transformations (FFTs) of electrocorticogram (ECoG) signals and averaging of somatosensory evoked potentials (SEPs) were used for assessing the impact of electrical stunning of ducks in a waterbath set to deliver a constant current of 150 mA, 600 Hz alternating current (AC) for 4 s. The effectiveness of stunning was determined on the basis of induction of epileptiform activity in the ECoG followed by a decrease in total power content to less than 10% of pre-stun values and abolition of SEPs. 2. One out of 10 birds was killed by the stun. FFT analysis of the ECoG signals of the remaining 9 birds showed that only one bird had a decrease of the total power to less than 10% of the pre-stun values for up to 70 s post-stun. The SEPs were retained in 6 out of 9 ducks and and 4 of them retained the evoked responses throughout the post-stun period. In the two birds showing abolition of SEPs, this was associated with a decrease in the total power content to below 10% of the pre-stun value. 3. The present experiment confirmed that the abolition of SEPs and the decrease of the total power below 10% of the pre-stun value for assessing unconsciousness after an electrical stunning in various species are also applicable to ducks. Based on this, it is concluded that electrical waterbath stunning of ducks using 150 mA of 600 Hz AC is ineffective.     

Effect of current frequency during electrical stunning in a water bath on somatosensory evoked responses in turkey's brain

Somatosensory evoked responses (SEP) in a turkey's brain were determined after water-bath stunning with a 150-mA (constant current) delivered with 50, 300 or 600 Hz, or with 75 mA, delivered with 50-Hz alternating current (AC) in order to evaluate the effectiveness of stunning. Ninety-four BUT 9 turkey hens 12 weeks of age were surgically implanted with EEG recording and left wing nerve stimulating electrodes 4 hours before stunning. They were individually stunned by immersion of the head and upper part of the neck in a water bath for 4 s. Using a 150-mA current, all birds stunned at 50 Hz showed cardiac arrest and a flat EEG immediately after the stun with no SEP recovery. The incidence of cardiac arrest at stunning decreased with increasing current frequency but SEP were lost in all birds. In birds that survived the stun, the duration of SEP abolition was on average 69 and 34 seconds at 300 and 600 Hz, respectively. Stunning with a 75-mA AC, delivered with 50 Hz, induced cardiac arrest in 32 per cent of turkeys. SEP were abolished in only 71 per cent of the birds that survived the stun, with an average duration of SEP of 66 seconds. The results indicate that increasing the frequency of a 150-mA AC current leads to a decreased stunning efficiency. A current of 75 mA per bird is unacceptable since 29 per cent of the birds do not show SEP abolition.     

Effect of electrical stunning frequency on ventricular fibrillation, downgrading and broken bones in broilers, hens and quails

The effect of stunning current frequency on the incidence of ventricular fibrillation was determined in broilers and hens. When a pulsed unipolar square wave (DC) was used the incidence of ventricular fibrillation decreased as the frequency was increased beyond 125 Hz. When a sinusoidal AC was used, 50 Hz killed some of the birds whereas at the corresponding r.m.s. currents no birds experienced a ventricular fibrillation with 1500 Hz. In quail, it was found that between 45 and 110 mA (50 Hz) all birds experienced a ventricular fibrillation. The effect of 50, 200 and 350 Hz square wave DC on carcass downgrading was examined in broilers, and there were no differences between the groups. It was concluded that there were few advantages from using high frequency stunning currents in poultry.     

The role of electrical stunning, bleeding and plucking efficiency on the downgrading of chicken carcases

This study examined the effects of inducing a cardiac arrest at electrical stunning, in combination with impaired bleeding and severe plucking, on the incidence of haemorrhages and broken bones in chicken carcases. It was concluded that with the possible exception of breast muscle haemorrhages none of the downgrading conditions were attributable solely to electrical stunning. Poor neck cutting, too severe plucking and flapping of the wings before death also played a part.     

Efficiency of bleeding of broilers after gaseous or electrical stunning

The efficiency of bleeding of broilers (g blood/kg liveweight) was measured after stunning them with either 45 per cent carbon dioxide in air for two minutes or with 2 per cent oxygen (achieved by displacing air with argon) for two minutes or with an electric current (77 or 104 mA at 50 Hz for four seconds). The results indicated that the initial rate of bleeding was higher in the electrically stunned broilers with non-fibrillated hearts than in the gas stunned broilers and electrically stunned broilers with fibrillated hearts. This difference was significant up to 60 seconds after neck cutting (P less than 0.05) but after 140 seconds all the broilers had bled out to a similar extent (30 to 33 g/kg liveweight). It is concluded that after gas stunning the time interval between neck cutting and scalding should be 60 to 140 seconds.     

Effect of very low pulsed direct currents at high frequency on the return of neck tension in broilers

Broiler chickens were stunned electrically for one second or 10 seconds with a unipolar pulsed direct current (DC) at 550 Hz. The effectiveness of the stun was assessed from the birds' behaviour. All the birds were stunned effectively when more than 15 mA true root mean square DC was applied for either period. An increase in the duration of the applied current resulted in an increased duration of unconsciousness. However, the unipolar pulsed DC at 550 Hz did not induce cardiac arrest, and it must therefore be accompanied by a prompt and effective neck cut, severing both carotid arteries.     

Assessment of the effectiveness of head only and back-of-the-head electrical stunning of chickens

1. The study assesses the effectiveness of reversible head-only and back-of-the-head electrical stunning of chickens using 130–950 mA per bird at 50 Hz AC.

2. Three trials were conducted to compare both stunning systems: (a) behavioural assessment of return of consciousness, (b) insensibility to thermal pain, and (c) assessment of return of brain activity with visually evoked potentials (VEPs).

3. Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers.

4. Stunning across the back-of-the-head delayed the time to return of brainstem function compared to stunning with standard head-only electrodes. Additionally, back-of-the-head stunning produced a more prolonged period of electroanalgesia compared to head-only.

5. Based on examination of return of brain function with VEPs in hens, back-of-the-head stunning produced a shorter-lasting stun than standard head-only. However, even for standard head-only, the stun was notably shorter than previously reported. In some birds, brain function had returned within 9 s after the end of stunning.

6. The results suggest that some birds may recover consciousness prior to or during the neck cut. Based on these findings, back-of-the-head stunning and standard head-only stunning of hens should not be recommended without further development.

     

Effect of stunning on spontaneous physical activity and evoked activity in the brain

1. The effect of stunning current on the time to recovery of physical activity, and on somatosensory evoked potentials (SEPs) in the brain, was examined in broiler chickens. 2. Increasing stunning current was associated with an increase in the time to recovery of tension in the neck muscles and with an increase in the incidence of loss of SEPs. 3. Currents greater than 105 mA per bird provided 52 s or more of apparent insensibility; currents greater than 120 mA were associated with absence of SEPs following the stun.     

Effect of stunning current on carcase quality in chickens

The effect of the stunning current at slaughter on carcase quality was examined in 1845 broiler chickens. As the current was increased there was an increase and then a decrease in the incidence of red wingtips and in haemorrhages of the wing veins and the shoulder joint. The incidence of deep breast muscle haemorrhages increased above about 130 mA, and the incidence of broken bones increased between 75 and 170 mA. The incidence of carcase defects was lowest when either less than 130 or greater than 190 mA was used to stun the birds.     

Effect of stunning current on downgrading in turkeys

1. Turkeys were electrically stunned with 75, 150 or 250 mA per bird to examine the effect of current on carcase quality defects. The defects that were examined included skin and muscle haemorrhaging, broken bones and engorgement of veins with blood. 2. The incidence of ventricular fibrillation at these currents was 26, 97 and 100%, respectively. Haemorrhaging in the breast muscle was the only variable affected by stunning current and was greatest when 250 mA was used. 3. It is recommended that turkeys should be stunned with 150 mA per bird.     

Broken bones in chickens: Effect of stunning and processing in broilers

1. Broilers and broiler carcases, sampled immediately before the stunner, at the end of the processing line and from a supermarket company, were physically dissected to determine the incidence of broken bones.

2. Over 95% of the frozen broilers from the supermarket company had broken bones and there were between 3 and 4 breaks per carcase. Only 3% of live birds had broken bones so most of the carcase damage must have been caused by processing.

3. The effect of 100, 200 and 300 V electrical stunning on the incidence of broken bones was investigated: increasing voltage resulted in an increase in the incidence of broken bones in the collar region.     

Effects of electrical water bath stunning current frequencies on the spontaneous electroencephalogram and somatosensory evoked potentials in hens

1. The effectiveness of water bath electrical stunning of chickens with a constant root mean square (rms) current of 100 mA per bird delivered for 3 s using 100, 200, 400, 800 and 1500 Hz sine wave alternating current (AC) was investigated in layer hens. The quantitative changes occurring in the electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) were used to determine the effectiveness of stunning. The changes occurring in the EEG were evaluated using Fast Fourier Transformations (FFT) and the SEPs were averaged to determine whether they were present or abolished. 2. The results of FFT indicated that stunning of chickens with a constant rms current of 100 mA per bird using 100 or 200 Hz induced epileptiform activity in all the hens, immediately followed by a reduction in the total (2 to 30 Hz) and relative (13 to 30 Hz) power contents in the EEG frequency bands indicative of unconsciousness and insensibility. The SEPs were abolished in the majority of hens stunned with 100 Hz and all the hens stunned with 200 Hz. 3. By contrast, stunning using 400, 800 or 1500 Hz failed to induce epileptiform activity in all the birds, the total and relative power contents in the EEG frequency bands showed a substantial increase, rather than reduction, and the SEPs were also retained in the majority of chickens. It is therefore suggested that stunning using these frequencies failed to stun them satisfactorily. In these birds, occurrence of a painful arousal, rather than unconsciousness, could not be ruled out. 4. It is therefore suggested that water bath electrical stunning of chickens with a minimum rms current of 100 mA per bird delivered using 100 or 200 Hz would be adequate to ensure bird welfare under commercial conditions, provided both the carotid arteries in the neck are severed at slaughter. On humanitarian and bird welfare grounds, a rms current of greater than 100 mA per bird should be applied whilst using frequencies of 400 Hz or more of sine wave AC for water bath electrical stunning of chickens.