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Biomedical subjects

N G Gregory

Publications and source records attributed to N G Gregory.

At least 73 records · Page 4Linked to original sources
PubMed1990

An evaluation of the effectiveness of handheld stunners for stunning chickens.

Two experiments were conducted in which the spontaneous physical behaviour, spontaneous electroencephalogram (EEG) and somatosensory evoked potentials were examined in chickens stunned with a handheld, head-only stunner operating at 117 v. Thirteen of 14 birds lost their evoked potentials after stunning, and when they were exsanguinated within 15 seconds they did not regain them before they died. The remaining bird appeared to have evoked potentials after stunning but there was a movement artifact in its EEG and it is possible that they were not genuine responses. When head-only stunning was applied to 50 birds for one second the birds appeared to be stunned instantaneously, in terms of their spontaneous physical behaviour. However, they recovered more rapidly than 40 birds which were stunned for seven seconds. It was concluded that the handheld stunner can stun a bird effectively, and provided that the bird's neck is cut promptly, can kill it humanely.

Abattoirs↗
PubMed1990

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.

Abattoirs↗
PubMed1990

Effect of carbon dioxide stunning on somatosensory evoked potentials in hens.

The spontaneous electroencephalogram (EEG) and somatosensory evoked potentials (SEPs) were examined in 17 hens before and during stunning in 45 per cent carbon dioxide. The results indicated that EEG suppression and loss of SEPs occurred in 21 +/- 4 s and 30 +/- 2 s, respectively, after exposure to carbon dioxide, eventually leading to EEG silence in 101 +/- 18 s. Convulsions occurred 15 seconds after the loss of SEPs, suggesting that the hens convulsed while they were unconscious. It is concluded that the induction of anaesthesia can be rapid in carbon dioxide stunning and in this respect carbon dioxide is potentially suitable for stunning poultry under commercial conditions.

Abattoirs↗
PubMed1990

Effect of rate of induction of carbon dioxide anaesthesia on the time of onset of unconsciousness and convulsions.

The effect of different rates of induction of carbon dioxide anaesthesia on the time to loss of consciousness was investigated in broilers and hens. In experiment 1, 24 and 17 broilers, respectively, were exposed to 45 per cent carbon dioxide within 8 or 18 seconds (accession time). In experiment 2, 18 to 20 broilers and hens were exposed to either 35, 45, 55 or 65 per cent carbon dioxide within 8 seconds. The results indicated that, in general, the rate of accession is more critical than the final concentration of carbon dioxide; however, in 35 per cent carbon dioxide an exposure time of longer than 5 minutes is required to kill the birds. The time to sustained eye closure, time to onset of clonic and tonic convulsions and the duration of convulsive episodes were shorter in broilers than in hens. It is suggested that under commercial situations a final concentration of 55 per cent carbon dioxide would be suitable for killing broilers and hens.

Abattoirs↗
PubMed1990

Investigation into the batch stunning/killing of chickens using carbon dioxide or argon-induced hypoxia.

Three hundred and twenty broilers were stunned for 2 minutes in batches of 10 per crate in four treatments: 45 per cent carbon dioxide; 55 per cent carbon dioxide; 2 per cent oxygen, or 5 per cent oxygen presented as air diluted by argon. The number of survivors and the time to resumption of consciousness were recorded using the time to eye opening and response to comb pinching as indicators of consciousness. In 45 per cent and 55 per cent carbon dioxide and 2 per cent oxygen, 28, none and eight birds, respectively, survived out of 100 in each group. In 5 per cent oxygen the birds were still fully conscious after a 2 minute exposure period, and the test was discontinued. The time to recovery could be rapid after stunning in both the gases. It is suggested that a concentration of 55 per cent carbon dioxide or less than 1 per cent oxygen are required to kill broilers within a 2 minute exposure period, and that care should be taken to ensure that there is sufficient turbulence within the stunning chamber to avoid air pockets being trapped between the birds.

Abattoirs↗
PubMed1989

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.

Abattoirs↗
PubMed1989

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.

Abattoirs↗
PubMed1989

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.

Animals↗
PubMed1989

Effect of ventricular fibrillation at stunning and ineffective bleeding on carcase quality defects in broiler chickens.

1. This experiment was concerned with whether ineffective bleeding could exacerbate the incidence of haemorrhagic conditions in broiler carcases, when ventricular fibrillation (VF) was induced at stunning. 2. Broiler chickens were electrically stunned with 81 mA per bird and then allocated to three treatments. About 67% experienced a VF at stunning and half of these birds were bled out before processing while the other half were processed without being bled out. The birds which did not experience a VF at stunning were bled out before being processed. The carcases were subjectively graded for haemorrhagic conditions. 3. Inducing a VF at stunning caused increases in the incidence of red wingtips and haemorrhaging at the humerus-radius joint in the birds which were bled out. There were no other obvious effects of inducing a VF on carcase downgrading. 4. Failure to bleed the chickens which had a VF at stunning resulted in high incidences of red wingtips, red necks, haemorrhaging at the humerus-radius joint and red sternal feather tracts. It was concluded that bleeding efficiency was important in influencing the expression of these characteristics when a VF occurred at stunning.

Animals↗
PubMed1989

Beta-adrenergic responsiveness in stress-sensitive and stress-resistant pigs.

This study investigated whether enhanced metabolic responsiveness to beta-adrenergic stimulation might explain the liability of the stress-sensitive pig to develop an acidosis during stressful situations. Blood lactate, pH, PCO2 and heart rate response to an intravenous infusion of isoprenaline were examined in three lines of pentobarbitone anaesthetized, atropinized pigs. The lines were Pietrain X Hampshire which had been selected over eight generations for a positive reaction to the halothane test (stress-sensitive); Pietrain X Hampshire which had been selected over eight generations for no reaction to the halothane test (stress-resistant) and British Landrace which had been selected over four generations for a positive halothane reaction (stress-sensitive). The metabolic responses to isoprenaline were greater in the stress-sensitive Pietrain X Hampshire line than the stress-resistant line. The stress-sensitive Landrace pigs, however, had smaller changes in pH and PCO2 in response to isoprenaline than the stress-resistant Pietrain X Hampshire pigs. This inconsistent trend across the three lines led to the conclusion that enhanced beta-adrenergic responsiveness was not the likely cause of stress sensitivity.

Animals↗
PubMed1988

Turkey slaughtering procedures: time to loss of brain responsiveness after exsanguination or cardiac arrest.

The effect of inducing a cardiac arrest or severing both carotid arteries on the spontaneous and visual evoked electrical activity in the brain were examined in anaesthetised turkeys. The time to loss of evoked activity was greater following the cardiac arrest. It was concluded that the potential humanitarian advantages of inducing a cardiac arrest at stunning are less pronounced in the turkey than for other poultry species.

Abattoirs↗
PubMed1987

Duration of wing flapping in chickens shackled before slaughter.

Shackling can induce wing flapping in chickens. In this survey of 30 chicken processing plants the proportion of birds flapping their wings had usually subsided to less than 0.5 per cent after the birds had been conveyed 2 m away from the shackling area. Thereafter, there were many causes of wing flapping, of which the following were thought to be important; tight fitting shackles on the birds' shanks, electric shocks at the water bath stunner before stunning, sudden bright sunlight, bends in the line, temporary loss of visual contact between neighbouring birds, and unevenness in the line which jolted the birds. If it is decided that legislation is required to prescribe a minimum 'hang-on' period before stunning it is suggested that birds should not be put through the stunner less than 12 seconds after shackling because after this time 99.7 per cent of the birds had stopped flapping.

Abattoirs↗
PubMed1987

An assessment of carbon dioxide stunning in pigs.

The vocalisation patterns of pigs subjected to stunning in 86 per cent carbon dioxide in a commercial abattoir suggested that narcosis began 30 to 39 seconds after the start of the immersion procedure. The spontaneous and reflex physical behaviour of the pigs after immersion indicated that they were effectively stunned, but the majority of the animals were not considered to be brain-stem dead. None of the carcases showed pale soft exudative meat.

Abattoirs↗
PubMed1986

Effect of slaughter on the spontaneous and evoked activity of the brain.

The principal blood vessels in the neck which are severed at slaughter in commercial poultry processing plants are described. Mechanical slaughtering methods often severed the spinal cord without cutting the carotid arteries. The manual method of slaughter cut one carotid artery plus one jugular vein. The effects of 9 different slaughtering methods on spontaneous and evoked electrical activity in the brain were examined in anaesthetised chickens and ducks. Severing the spinal cord without cutting the carotid arteries was found to result in death from asphyxia, and cutting one carotid artery plus one jugular vein was one of the slowest methods of killing the birds. Inducing a cardiac arrest at electrical stunning was the quickest method of inducing death. Spontaneous activity in the brain was lost before visual evoked activity. The times before loss of spontaneous activity varied between 23 and 233 s according to the method of slaughter and loss of evoked activity ranged between 90 and 349 s after slaughter.

Abattoirs↗
PubMed1986

Effect of azaperone on cardiovascular responsiveness in stress-sensitive pigs.

The effect of intramuscular azaperone on the cardiovascular responses to stimulation of the sympathetic nervous system was examined in thiopentone-anaesthetized stress-sensitive pigs. Sympathetic stimulation was achieved with the Valsalva-like manoeuvre, and the intravenous tyramine, isoprenaline and phenylephrine tests. The responses were monitored as the changes in heart rate and blood pressure. Azaperone exerted an alpha adrenergic blocking action and possibly a mild beta adrenergic blocking effect. It also retarded pre-adrenoreceptor activation of heart rate. It is suggested that azaperone has peripheral actions which could contribute towards its prophylactic effect in preventing stress-induced deaths in pigs.

Animals↗
PubMed1986

Pig slaughtering procedures: time to loss of brain responsiveness after exsanguination of cardiac arrest.

The time taken for a conventional chest stick to produce the loss of flash-evoked responsiveness in the electrocorticogram of anaesthetised pigs was compared with a method involving fibrillation of the heart. On average severing the brachiocephalic trunk and anterior vena cava took 18 seconds to induce a loss of brain responsiveness, and inducing cardiac fibrillation took 19 seconds. It is concluded that a pig slaughtering method that stuns the brain and at the same time fibrillates the heart is likely to be more humane than the conventional slaughtering methods where there is a delay between the stunning and sticking operations.

Animals↗