Remote monitoring of electroencephalogram, electrocardiogram, and behavior during controlled atmosphere stunning in broilers: implications for welfare.

This study examined the welfare implications of euthanizing broilers with 3 gas mixtures relevant to the commercial application of controlled atmosphere stunning (CAS). Birds were implanted/equipped with electrodes to measure brain activity (electroencephalogram, EEG) and heart rate. These signals were recorded using a purpose-built telemetry-logging system, small enough to be worn by each bird in a spandex backpack. The birds were euthanized in a scaled-down CAS apparatus consisting of a conveyor belt passing through 2 compartments. Three gas environments were applied (8 birds per treatment): 1) anoxia (N(2) with <2% residual O(2), in both compartments), 2) hypercapnic anoxia (N(2) with 30% CO(2) and <2% residual O(2), in both compartments), and 3) a 2-phase approach with a hypercapnic hyperoxygenated anesthetic phase (40% CO(2), 30% O(2), and 30% N(2), in the first compartment, 80 s) followed by a second euthanasia phase (80% CO(2) in air, in the second compartment). All 3 CAS approaches effectively achieved nonrecovery states, and time to loss of consciousness for each bird was determined by visual determination of isoelectric EEG and by calculation of the correlation dimension of the EEG. Hypercapnic anoxia resulted in rapid unconsciousness and death; both anoxic treatments were associated with early onset prolonged wing flapping and sustained tonic convulsions as displayed in the electrophysiological recordings. These responses were seen in the period when consciousness remained a possibility. Hypercapnic hyperoxygenation (the 2-phase approach) was associated with respiratory disruption, but this treatment eliminated initial clonic convulsions in the stunning process, and tonic convulsions were not seen. These results suggest that the presence of O(2) in the first stage of CAS is associated with an absence of potentially distressing behavioral responses. The respiratory discomfort associated with hypercapnic hyperoxygenation is an issue. We propose that this may be compensated by a more gradual induction to unconsciousness, which eliminates the impact of other potentially negative experiences.

Right ventricular contractility in systemic sclerosis-associated and idiopathic pulmonary arterial hypertension.

Since systemic sclerosis (SSc) also involves the heart, the aim of the present study was to evaluate possible differences in right ventricular (RV) pump function between SSc-associated pulmonary arterial hypertension (PAH; SScPAH) and idiopathic PAH (IPAH). In 13 limited cutaneous SScPAH and 17 IPAH patients, RV pump function was described using the pump function graph, which relates mean RV pressure ((RV)) and stroke volume index (SVI). Differences in pump function result in shift or rotation of the pump function graph. (RV) and SVI were measured using standard catheterisation. The hypothetical isovolumic (RV) ((RV,iso)) was estimated using a single-beat method. The pump function graph was approximated by a parabola: (RV) = (RV,iso)[1-(SVI/SVI(max))(2)], where SVI(max )is the hypothetical maximal SVI at zero (RV), enabling calculation of SVI(max). There were no differences in SVI and SVI(max). Both (RV) and (RV,iso) were significantly lower in SScPAH than in IPAH ((RV) 30.7+/-8.5 versus 41.2+/-9.4 mmHg; (RV,iso) 43.1+/-12.4 versus 53.5+/-10.0 mmHg). Since higher pressures were found at similar SVI, the difference in the pump function graph results from lower contractility in SScPAH than in IPAH. Right ventricular contractility is lower in systemic sclerosis-associated pulmonary arterial hypertension than in idiopathic pulmonary arterial hypertension.

Controlled atmosphere stunning of broiler chickens. I. Effects on behaviour, physiology and meat quality in a pilot scale system at a processing plant.

1. The effects of controlled atmosphere stunning on the behaviour, physiology and carcase and meat quality of broiler chickens were studied experimentally in a pilot scale plant. 2. Gas mixtures tested were: single phase anoxic mixture (90% Ar in air, <2% O(2)); single phase hypercapnic anoxic mixture (60% Ar, 30% CO(2) in air, <2% O(2)); and biphasic hypercapnic hyperoxygenation mixture (anaesthetic phase, 40% CO(2), 30% O(2), 30% N(2); euthanasia phase, 80% CO(2), 5% O(2), 15% N(2)). 3. Anoxic stunning resulted in the least respiratory disruption, mandibulation and motionlessness, but most head shaking, leg paddling and twitching. Loss of posture occurred soonest with hypercapnic anoxia with the earliest and most twitching and wing flapping in individuals and earliest leg paddling. Biphasic birds were most alert, exhibited most respiratory disruption and mandibulation, and had the latest loss of posture and fewest, but longest bouts of wing flapping and least leg paddling and twitching. 4. Significant and sudden bradycardia and arrhythmia were evident with all gas mixtures and were not related solely to anoxia or hypercapnia. Birds stunned by Ar anoxia showed a slightly more gradual decline from baseline rates, compared with hypercapnic mixtures. 5. Few differences were found between gas mixes in terms of carcase and meat quality. Initial bleeding rate was slowest in biphasic-stunned birds, but total blood loss was not affected. Acceleration of post-mortem metabolism in anoxic-stunned birds was not sufficient to allow de-boning within 5 h without the risk of tough meat. 6. On welfare grounds and taking into account other laboratory and field studies, a biphasic method (using consecutive phases of anaesthesia and euthanasia) of controlled atmosphere stunning of broilers is potentially more humane than anoxic or hypercapnic anoxic methods using argon or nitrogen.

Controlled atmosphere stunning of broiler chickens. II. Effects on behaviour, physiology and meat quality in a commercial processing plant.

1. The effects of controlled atmosphere stunning on behavioural and physiological responses, and carcase and meat quality of broiler chickens were studied experimentally in a full scale processing plant. 2. The gas mixtures tested were a single phase hypercapnic anoxic mixture of 60% Ar and 30% CO(2) in air with <2% O(2), and a biphasic hypercapnic hyperoxygenation mixture, comprising an anaesthetic phase, 40% CO(2), 30% O(2), 30% N(2), followed by an euthanasia phase, 80% CO(2), 5% O(2), 15% N(2). 3. Birds stunned with Ar + CO(2) were more often observed to flap their wings earlier, jump, paddle their legs, twitch and lie dorsally (rather than ventrally) than those stunned with CO(2) + O(2). These behaviours indicate a more agitated response with more severe convulsions during hypercapnic anoxia, thereby introducing greater potential for injury. 4. Heart rate during the first 100 s of gas stunning was similar for both gases, after which it remained constant at approximately 230 beats/min for CO(2) + O(2) birds whereas it declined gently for Ar + CO(2) birds. 5. In terms of carcase and meat quality, there appeared to be clear advantages to the processor in using CO(2) + O(2) rather than Ar + CO(2) to stun broiler chickens, for example, a much smaller number of fractured wings (1.6 vs. 6.8%) with fewer haemorrhages of the fillet. 6. This study supports the conclusions of both laboratory and pilot scale experiments that controlled atmosphere stunning of broiler chickens based upon a biphasic hypercapnic hyperoxygenation approach has advantages, in terms of welfare and carcase and meat quality, over a single phase hypercapnic anoxic approach employing 60% Ar and 30% CO(2) in air with <2% O(2).

Behavioral responses of broilers to different gaseous atmospheres.

This study was conducted to determine the differences in behavioral response of broilers when they come into contact for the first time with gas mixtures that can be used for stunning. The six test groups were divided into four experimental groups that were exposed to gas mixtures used for stunning and two control groups that were exposed to atmospheric air. The different gas mixtures and their concentrations were a) air, no flow (control-); b) circulating air, flowing (control+); c) >90% Ar in air; d) 60% CO2 in air; e) 40% CO2 and 30% O2 in air; and f) 70% Ar and 30% CO2 in air. The behavior of the broilers before entering the gas tunnel, the number of birds that moved into the gas mixture, and the behavior in the gas mixture were recorded on video and analyzed afterward. No differences among the groups were observed in the number of broilers that walked into the gas tunnel or in the number of birds that tried to return to the cage. Exposure of broilers to the 70% Ar and 30% CO2 mixture resulted in the fastest loss of posture. The number of broilers exhibiting headshaking and gasping was least in the >90% Ar in air mixture. Convulsions were rarely seen in the 40% CO2 and 30% O2 mixture; the other gas mixtures resulted in severe convulsions. The experiment did not indicate that broilers could detect or avoid increased CO2 or decreased O2 levels when they come into contact with such atmospheres for the first time.

Controlled atmosphere stunning of poultry.

For more than 20 yr Stork PMT has carried out a lot of research into stunning and killing of poultry with electrical and mechanical methods and by applying gas mixtures. For the past 3 yr, research was carried out under the European umbrellas (AIR and EUREKA) together with BOC, The Spelderholt, CIVO, and Bristol University. This research program involved tests on broiler stunning or killing with various gas mixtures. The effect on meat quality, bleeding, and plucking was studied, as well as the use of gas as a humane way of killing broilers. The study of meat quality was based on tenderness tests conducted on the shear force principle, meat color, and drip and cooking losses. The percentage of blood loss in bleeding, blood spots, and the amount of blood in the veins in relation to the gas mixtures and time of hanging were measured. The effect of gas killing on the plucking characteristics was studied by determining the feather release force and product handling. The behavior of the birds, reflexes, the onset of convulsions, electroencephalograms, and evoked responses were studied in relation to the humanness of gas killing. Anoxia generated through argon or a mixture of argon and carbon dioxide or hypercapnic hypoxia seems to be very promising. The tests revealed that meat tenderness and drip losses will improve. The blood spots, especially those on the thighs and breasts caused by stunning and hanging, disappear altogether. It also appeared that animal welfare will be drastically improved. From a technological point of view, broiler killing in a controlled gas atmosphere is considered to be the optimal process. However, successful introduction of the process requires legislative changes and poultry processors must be made aware of its economic benefits.