Field Study of Control of Atmosphere Stunning in Poultry

Date:           April, 1997

Location:   Eye, Suffolk, U.K.

Observer:  J.P. Quine, D.V.M., P.O. Box 477, Cochrane, Alberta TOL OWO.

This study was initiated by the ANIMAL WELFARE FOUNDATION OF CANADA in response to reports by Drs. Temple Grandin and Mohan Raj, from the United States and the United Kingdom respectively, that aspects of electro-stunning techniques in poultry raised welfare concerns.

Controlled Atmosphere Stunning, (henceforth referred to as CAS), appeared to promise both welfare and processing advantages and an on-site evaluation of the operation was proposed to see if these advantages could be attained in a commercial operation.
 

Background

The practice of electro-stunning of poultry in processing plants has been a subject of debate in Europe and, to a lesser extent, in North America. Specifically these issues include uncrating and shackling of conscious birds, random pre-stun shocks and reported cases of birds recovering consciousness prior to scalding. Increasing the current will irreversibly impair brain function and induce cardiac arrest but the welfare benefits are offset by reduced carcass quality manifest by tissue hemorrhage and fractured bones.

Researchers at Bristol University, England, have explored the possibilities offered by CAS in an attempt to address the argued drawbacks of electro-stunning. Convincing evidence was also needed to dispel widely held reservations about the CAS technique. The proponents of gas stunning have presented credible evide nce that unconsciousness can be precipitated rapidly and that the convulsive phase is secondary to an unconscious state.

The use of high concentrations of CO2 was dismissed due to the pungency of this gas at lethal levels and the induced laboured breathing efforts associated with its use. Though forfeiting the economic advantages of CO2, a mixture of sixty percent Argon and thirty percent of CO2 plus Air, proved to be a reasonable compromise.
 

Observations

The Grampian Group plant is located at Eye, in Suffolk County which is north of London. Security was tight and entrance strictly controlled. Attention was directed at four specific areas of the operation. These are, unloading procedures, stunning, inspection of carcasses prior to neck cutting and carcass quality.

Trucks arrived at the plant with chickens uniformly packed in plastic crates loaded into modules. These modules were off-loaded with forklifts and smoothly placed onto conveyors located at the stunning unit. The conveyors lowered the birds and then traversed the length of the unit for about one and one half minutes. Viewing panels allowed the process to be seen from the outside of the chamber. Atmospheric conditions inside the tank were displayed on an adjacent panel and adjustments to variations inside the tank continued automatically.

Immediately following immersion in the tank, birds bobbed their heads two or three times and then fell over. No evidence of panic or excitement was observed. Exiting crates were closely examined for any signs of life in the recumbent birds, but none was noted. Neck cutting took place immediately following manual shackling of the carcasses.

In the boardroom, samples of meat from birds stunned by both gas and electricity were presented for comparison. Hemorrhages were clearly visible in the tissues subjected to electricity but the CAS birds showed no evidence of blood.

* Click HERE for a diagramme of the automated CAS process...



Summary of claimed benefits of CAS:

1. Minimal handling of live birds. Automated systems currently exist to harvest birds  into  crates and modules which are loaded into trucks for transport to the processing plants.

2. No shackling of live birds.

3. Fewer bone fractures and bruises with automated systems.

4. Cleaner, more quiet working atmosphere, as shackled birds are unconscious and there is no dust or noise from wing flapping.

5. Carcass quality is superior in CAS birds.
It would be unrealistic to expect processors to consider changing from existing, relatively inexpensive technology to more sophisticated equipment for welfare advantages alone. Recovery of costs can come about through less wastage and improved carcass quality. These factors were considered to be important in the United Kingdom market. However, further investigation is needed into processing and marketing in North America.
  
The author wishes to thank Dr. Mohan Raj for his generous contribution of time and discussion during the U.K. visit. Special mention to the representatives of Anglia Autoflow Industries and the Grampian Group. They illustrated how alliances between animal welfare proponents and industrial groups are possible and might occur in the future.

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