An evaluation of humane gas stunning methods for turkeys

The reactions of turkeys to the presence of either 90 per cent argon in air (anoxia), 72 per cent carbon dioxide in air or a mixture of 30 per cent carbon dioxide and 60 per cent argon in air with 3 per cent residual oxygen were tested. The majority of the turkeys did not avoid a feeding chamber containing either argon or the mixture of carbon dioxide and argon, but 50 per cent of the turkeys avoided a feeding chamber containing 72 per cent carbon dioxide in air. It is concluded that from the point of view of welfare, either 90 per cent argon in air or a mixture of 30 per cent carbon dioxide and 60 per cent argon in air, would be preferable to a high concentration of carbon dioxide for stunning/killing turkeys.

Pigs were exposed individually to either 90 per cent argon in air (anoxia), a mixture of 30 per cent carbon dioxide and 60 per cent argon in air (hypercapnic anoxia)...

The times to the loss of somatosensory evoked potentials (SEPs) and the onset of suppressed and isoelectric electroencephalogram (EEG) were investigated in turkeys as they were stunned with gas mixtures consisting of one of three mixtures: (A) 30 per cent carbon dioxide and 60 per cent argon in air (2 per cent residual oxygen and 8 per cent residual nitrogen); (B) 90 per cent argon in air (2 per cent residual oxygen and 8 per cent residual nitrogen); (C) 65 per cent carbon dioxide in air (7 per cent residual oxygen and 28 per cent residual nitrogen). The time to the loss of SEPs, EEG suppression and the onset of an isoelectric EEG, respectively, were 22, 16 and 35 seconds in mixture A, 44, 41 and 101 seconds in mixture B, and 15, 15 and 67 seconds in mixture C. Stunning turkeys with mixture A or B would be suitable under commercial conditions. Mixture C, containing 65 per cent carbon dioxide in air, is considered on humanitarian grounds to be unacceptable for stunning turkeys owing to the pungency of the carbon dioxide at this concentration.

The aversive effects of 90 per cent argon in air, 30 per cent carbon dioxide in air or 90 per cent carbon dioxide in air were investigated in slaughter weight pigs. Aversion was assessed from their reluctance to enter the three gaseous atmospheres to obtain a reward (apples). The pigs did not show any aversion to the inhalation of 90 per cent argon in air. The majority of the pigs did not show aversion to the presence of 30 per cent carbon dioxide in air. By contrast, the inhalation of 90 per cent carbon dioxide was aversive to the majority of the pigs. Fasting them for up to 24h prior to testing did not overcome the pigs ‘ reluctance to enter an atmosphere containing 90 per cent carbon dioxide.

Welfare implications of gas stunning pigs: 3. the time toloss of somatosensory evoked potential and spontaneous electrocorticogram of pigs during exposure to gases

The severity of respiratory distress occurring prior to loss of posture during exposure to: 20, 30, 40, 50, 60, 70, 80 or 90 per cent carbon dioxide in air; 2 or 5 per cent residual oxygen in argon; 30 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen; or 40 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen, was subjectively determined in pigs from their behaviour. The results indicated that exposure to 2 per cent oxygen in argon (anoxia) induced minimal respiratory distress, 30 per cent carbon dioxide in argon with 2 per cent residual oxygen induced a moderate distress and exposure to all the concentrations of carbon dioxide in air induced severe respiratory distress in the pigs. From the animal welfare point of view, using 2 per cent oxygen in argon (anoxia) appears to be the optimum choice for gas stunning pigs. Secondly, a mixture of 30 per cent carbon dioxide in argon with 2 per cent residual oxygen is preferred to 90 per cent carbon dioxide in air.

ASSIMILATION AND RESPIRATION OF EXCISED LEAVES AT HIGH CONCENTRATIONS OF CARBON DIOXIDE

Electrical waterbath stunning is the most common method used to stun poultry under commercial conditions. The voltage supplied to a multiple bird waterbath stunner must be adequate to deliver the required minimum current to each bird. High frequency (> 300 Hz) electrical waterbath stunning needs further investigation to determine its efficiency. It should always be followed by a prompt neck cutting procedure where all the major blood vessels in the neck are severed. Irrespective of the waveform or frequency of the currents employed, constant current stunners should be installed under commercial conditions to ensure that the minimum currents are delivered to individual birds in waterbath stunners. Head only electrical stunning of poultry is being investigated in detail and there is scope for commercial development. Important features include (a) a constant current capable of delivering a preset current, (b) a bird restraining conveyor and head presentation devices enabling the stunning tongs to be accurately placed, (c) more effective electrical stunning tongs in terms of delivering necessary currents while using low voltages, and (d) induction of cardiac arrest immediately after stunning to eliminate wing flapping. Stunning/killing of poultry still in their transport containers using gas mixtures would appear to be the best future option as far as bird welfare is concerned. However, birds can also be stunned/killed on a conveyor using gas mixtures, thereby eliminating the stress associated with the shackling of live birds before electrical stunning. Under the conveyor system birds should be presented to the gas mixtures in a single layer. Within gas mixtures a minimum of 90% argon in air would appear to be the first choice. A mixture of 30% carbon dioxide and 60% argon in air is better than using a high concentration of carbon dioxide in air, and is therefore considered to be the second choice. A two stage system that involves firstly stunning broilers with a low concentration of carbon dioxide and then killing them with a high concentration of carbon dioxide can be used by those who wish to use this gas for economic reasons. The two stages should be distinctly separated so that the birds are stunned well before exposure to a high concentration of carbon dioxide in air. In comparison with carbon dioxide alone, a mixture of 30% oxygen and 40% carbon dioxide in air prolongs the induction of anaesthesia and the exposure time required to kill the birds. The addition of oxygen to carbon dioxide may therefore not have any benefit to bird welfare or the processors. Mechanical stunning of poultry using penetrating captive bolts or non-penetrating mushroom headed bolts has been developed. However, stunning with these devices results in very severe wing flapping and further research is necessary to find ways of alleviating this problem.

SINCE blood has a pH of about 7.4, media used for organ and tissue culture are usually adjusted to this hydrogen ion concentration. However, when the chemically defined medium BGJb1 was first formulated, sodium bicarbonate was added in excess (3.5 g/l.), with the result that the medium had a pH of 7.68 when equilibrated with 5 per cent carbon dioxide in air. Mouse fallopian tubes continued to function2 and embryonic long bones developed1 under these alkaline conditions. Paff3 studied the effect of hydrogen ion concentration on embryonic chick femora cultivated on plasma clots in the presence of both air and 5 per cent carbon dioxide in air. The pH of the media under these conditions was 7.8–8.0 and 7.0–7.3 respectively. After cultivation for 14 days, the femora grown at the lower pH contained more bone and had a higher calcium content. However, the conditions required for mineralization may be quite different from those needed for cell division and cellular hypertrophy in the cartilaginous rudiment. We have, therefore, investigated the influence of hydrogen ion concentration on the growth of cartilaginous tibiotarsi of the embryonic chick. This was done by varying the bicarbonate concentration of the medium while maintaining a constant atmosphere of 5 per cent carbon dioxide in air.

A Study of Gastric Secretions in Chronic Obstructive Pulmonary Emphysema

Extracellular glycollate is liberated by Chlorella pyrenoidosa during growth in medium bubbled with air or 3 per cent carbon dioxide in air. With air the rate of release of glycollate per cell decreases, with 3 per cent carbon dioxide it increases, with increase in cell number. Glycollate is released during short-term experiments when C. pyrenoidosa, grown under low light and high carbon dioxide, is transferred suddenly to high light and low carbon dioxide. No other combina tion of these factors produces a comparable release of glycollate. The quantity of glycollate released in short-term experiments increases exponentially with the relative growth-rate of the culture from which the cells are derived. A crucial condition for maximum glycollate release is that growth of the culture prior to the experiment should not be limited by carbon-dioxide concentration. The effect of pH is related to its effect on growth-rate; i.e. C. pyrenoidosa has a lower relative growth-rate at pH 8 3 and produces correspondingly less glycollate than faster growing cultures at pH 6-4. During short-term experiments under high light and low carbon dioxide the rate of glycollate release drops after 50-100 minutes suggesting exhaustion of the glycollate precursor.

Characteristics of the large-scale circulation during episodes with high and low concentrations of carbon dioxide and air pollutants at an arctic monitoring site in winter

The efficacy for the euthanasia of day-old chicks of mixtures of carbon dioxide and air, or carbon dioxide and argon containing 1, 2 or 5 per cent residual oxygen, or argon containing 1 or 2 per cent residual oxygen was tested in three experiments. The time to the onset of unconsciousness of individual chicks, determined from the time to loss of posture, was similar during their exposure to 2 per cent oxygen in argon, 20, 30 or 40 per cent carbon dioxide in argon with 2 per cent residual oxygen, or 90 per cent carbon dioxide in air. The exposure of chicks in batches of 20 to a mixture of 20, 30 or 40 per cent carbon dioxide in argon resulted in the death of all the chicks within two minutes. However, a residual oxygen level of 5 per cent in these mixtures resulted in the survival of some chicks for longer than two minutes. With argon alone the level of residual oxygen was critical; less than 2 per cent was essential to achieve 100 per cent mortality within three minutes, and a rise from 2 to about 3 per cent resulted in up to 20 per cent of the chicks surviving for seven minutes.

The effect of breathing 2.5 to 10 per cent carbon dioxide in air on specific airway conductance was determined by plethysmography in 9 normal subjects and in 8 subjects with mild asthma. In 9 normal subjects, during breathing of 5, 7.5, and 10 per cent carbon dioxide, mean (± SE) values of specific airway conductance decreased by 15.8 ± 6.1, 24.4 ± 6.0, and 28.4 ± 7.9 per cent with increases in end-tidal carbon dioxide tension of 5.0 ± 1.6, 12.3 ± 2.3, and 20.2 ± 2.5 mm Hg, respectively. These changes were not significantly affected by prior administration of atropine or propranolol except that atropine prevented the decrease in specific airway conductance during 5 per cent carbon dioxide breathing. Isocapnic hyperventilation decreased specific airway conductance (15 ± 6 per cent) but to a lesser extent than during similar increases in ventilation due to breathing of 10 per cent carbon dioxide. In contrast, in 8 subjects with asthma, specific airway conductance did not change during carbon dioxide breathi...

Changes in the somatosensory evoked potentials and spontaneous electroencephalogram of hens during stunning with a carbon dioxide and argon mixture