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

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.

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.

Spontaneous electroencephalograms (EEG) and somatosensory evoked potentials (SEPS) were recorded in turkeys while they were kept in an atmosphere of either 49 or 86 per cent carbon dioxide in air. The time to the loss of SEPS was not related to the concentration of carbon dioxide, but the time to the onset of an isoelectric EEG was shorter at the higher concentration of carbon dioxide. In comparison with other gas stunning methods it was considered that stunning with these high concentrations of carbon dioxide would not have any welfare advantages over stunning in argon with 2 per cent residual oxygen or in a mixture of 30 per cent carbon dioxide and 60 per cent argon in air.

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)...

1. Six week-old broiler chickens implanted with electroencephalogram (EEG) recording and somatosensory stimulating electrodes were exposed to either 90% argon in air, a mixture of 30% carbon dioxide and 60% argon in air or a mixture of 30% oxygen and 40% carbon dioxide (balance nitrogen) for 2 min, to determine the times to onset of changes in spontaneous EEG and the loss of somatosensory evoked potentials (SEPs) and thus unequivocal loss of consciousness. 2. In addition, after a 2 min exposure to the carbon dioxide-oxygen mixture, some broilers were allowed to recover in air and their EEGs and SEPs were continuously recorded until the return of normal EEG and SEPs. During this period, the time to return of response to comb pinching was also determined in 10 broilers. 3. All broilers exposed to either argon or the carbon dioxide-argon mixture died within 2 min, whereas, only 3 out of 17 broilers died during the 2 min exposure to the carbon dioxide-oxygen mixture. 4. During exposure to argon, unlike the other 2 gas mixtures, the majority of broilers showed high amplitude, low frequency electrical activity in the EEG on average at 10 s. The mean times to onset of EEG suppression were 17, 19 and 40 s after exposure to argon, the carbon dioxide-argon mixture and the carbon dioxide-oxygen mixture, respectively. An isoelectric EEG occurred on average at 58 and 41 s after exposure to argon and the carbon dioxide-argon mixture, respectively. An isoelectric EEG did not occur in broilers which were exposed to the carbon dioxide-oxygen mixture. 5. The SEPs were abolished in broilers on average 32 and 24 s after exposure to argon and the carbon dioxide-argon mixture, respectively. During exposure of broilers to the carbon dioxide-oxygen mixture the SEPs were abolished in the majority of birds on average at 47 s, however, 2 out of 14 birds retained their SEPs for the entire period of 2 min exposure to this gas mixture. 6. During the recovery after exposure to the carbon dioxide-oxygen mixture, response to comb pinching and SEPs returned either at the time of, or soon after, the onset of high frequency electrical activity in the suppressed EEG of broilers. The mean times to return of response to comb pinching and SEPs were 52 and 43 s, respectively. 7. Based on the time to onset of EEG suppression or loss of SEPs, exposure of broilers to either 90% argon in air, or a mixture of 30% carbon dioxide and 60% argon in air, resulted in quicker loss of consciousness than during exposure to a mixture of 40% carbon dioxide, 30% oxygen and 30% nitrogen. The time to return of consciousness after a 2 min exposure to the carbon dioxide-oxygen mixture was also found to be rapid.

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

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

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.

Optimization of environmental factors affecting tertiary treatment of municipal wastewater by Chlorella protothecoides in a lab scale photobioreactor

The concentration and isotopic abundances of carbon dioxide in rural and marine air

BACKGROUND: Elevated levels of carbon dioxide in gym air can diminish the benefits of physical activity and pose health risks for children.. AIM: to access carbon dioxide concentration in the air of school gyms during physical education classes. MATERIAL AND METHODS: A total of 612 measurements were taken to estimate the concentration of carbon dioxide in the air. These measurements were conducted in two separate gymnasiums: in Gym 1, designated for primary classes with an area of 77 m2, and Gym 2, used by middle and high school students with an area of 293 m2. Measurements were taken at 12 different points, both around the perimeter and in the central part of each gym. The height when measuremenmts were taken ranged from 0 to 230 cm. To assess the carbon dioxide concentration in the gym air, the background level was calculated based on GOST 30494-2011 standards (761.5 ppm). Student’s t-tests for independent samples were used to compare the data. Additionally, a regression analysis was utilized to estimate the spatial distribution of carbon dioxide within the gymnasiums. RESULTS: In Gym 1, the initial concentrations ranged from 845 to 1267 ppm, slightly exceeding the expected throughput. Throughout the training session, the carbon dioxide content increased by 1.6 to 2.3 times. By the end of the session, the carbon dioxide content reached 1934 to 1948 ppm at an estimated respiration level of 1.0 to 1.9 m. In Gym 2, the carbon dioxide content increased by 1.1 to 1.2 times by the end of the class. At a height of 0.0 to 1.7 m, the concentration of carbon dioxide was measured at 1016 to 1023 ppm. CONCLUSION: After 20 minutes of training at the expected intensity, carbon dioxide levels in the air exceed not only the background level of 761.5 ppm, but also the permissible level of 1000 ppm. This study highlights the importance of daily monitoring of carbon dioxide levels in school gymnasiums during training sessions and sporting events. Such monitoring is crucial for ensuring the health and safety of students and athletes.

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.

In the wheat cylinder bioassay technique as previously used here 5 sections have been enclosed in a 2 X f in. assay tube together with 0-5 ml. of the test solution. A method developed for estimating the amount of carbon dioxide which accumulates in these tubes through the respiration of the enclosed sections has shown that the level can rise to 20 per cent, after 24 hrs. at 25° C. In the presence of a 100 p.p.m. IAA (6x io~4 M.) test solution, growth of 5 enclosed sections is depressed from 8 hrs. onwards and they eventually shrink, releasing their accumulated IAA back into the solution. The growth of sections under various gas mixtures of carbon dioxide in air has also been followed and these experiments show that section length is reduced approximately linearly with respect to increasing carbon dioxide concentration up to 20 per cent, in air, both in the presence and absence of a 100 p.p.m. IAA solution. The slope of the fitted regression line, however, is much steeper when the test solution contains IAA—i.e. there is a large interaction. In the presence of IAA, growth-time data show that a reduction in the growth rate, as compared with that in normal air, can be detected after only 4 hrs. at the highest carbon dioxide concentration. In the absence of IAA, high concentra tions of carbon dioxide accelerate growth during the first 8 hrs. of the assay but depress it later. The mechanism of action of this interaction is unknown but it is not shown at very high concentrations of IAA, e.g. 1,000 p.p.m. (6x io-3 M.).

On the physiological action of carbon dioxide on cortex and hypothalamus

Carnations: effects of high concentrations of carbon dioxide on flower physiology and longevity