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

Abstract

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

“…For each scan, the observer selected the first observable bird passing nearest the window camera from which to record its behaviour, with the provisos that the chamber was full of birds and the conveyor was moving to maintain condition consistency. These provisos occasionally meant the scan was delayed by up to a maximum of 2 min, but on average only 5 s. The behaviour categories recorded were similar to those used by Abeyesinghe et al (2007) in the pilot scale system with the addition of some new postural categories. The bird's posture was described as: i) lie bird lying (ventrally, dorsally or laterally) with body in contact with the conveyor and supine head; ii) sit -bird sitting with sternum in contact with the conveyor with an erect head; and iii) stand -bird standing upright on two legs.…”

“…Many of the materials and methods used in this experiment were similar to those reported in the accompanying paper (Abeyesinghe et al, 2007). Groups of mature broiler chickens were stunned by gas in a commercial processing plant using one of two gas mixtures.…”

“…The methods used to observe the behavioural and physiological reactions of the birds to CAS are described by Abeyesinghe et al (2007) and measurements were made daily for three days with each gas treatment applied on each day. The gas treatments were applied sequentially while the processing line was running at 9000 birds/h.…”

“…All birds used in paired batches originated from the same flock. Physiological measurements of heart and respiration rate were made on a total of 90 individuals (15 per treatment per day), each of which was fitted with a telemetric/logging system mounted on a body harness (Lowe et al, 2007; method described in Abeyesinghe et al (2007)). Measurements were made for 60 s to establish a baseline while the bird was sitting on a table adjacent to the loading conveyor.…”

“…This paper is the last in a series (Abeyesinghe et al, 2007;Lowe et al 2007;McKeegan, 2004;McKeegan et al, 2006;2007) reporting the results of this project.…”