In poultry processing plants poultry is roughly stunned by means of 1. electrical shock, 2. gas mixtures or 3. none (ritual slaughter).
ad.1: In electrical stunning the birds heads are dragged through an electrified water bath. In this way an effective anaesthetic is created. Different legislations apply. In some countries “stun-to-kill” is required from the point of animal welfare. Although this process may lead to more bone breakage and hemorrhagic spots. When the anaesthetising process is carried out well, this is mainly in favour for animal welfare. Nevertheless, there are hygienic aspects involved too. A continuous water-flow through the reservoir reduces cross contamination within this reservoir (especially if the counter current principle is applied).
ad. 1a: A recent development in the so called head to head stunning. Here the head is fixed in a device which consists of two electrodes. An electric current is lead directly through the head.
ad 2: A new development is the gas-stunning process, where both animal welfare and quality are improved. Different gas mixtures are applied such as mixtures of air and Argon; Argon and CO2 or CO2 N2 plus O2. (Lambooij et al, 1999) .
ad 3: Poultry is killed without any stunning for Halal or Kosjer slaughter.
Food safety issues: Ingestion or inhalation of contaminated water from the electrocution tank, cross contamination through the transportation belt inside the gas tunnel, uncontrolled wingflapping and spread of dust and blood while bleeding without stunning.
Poultry is killed by cutting the carotid artery (left, right, double sided or under the tongue). This is either done automatic or manual and in general takes place 10 seconds after stunning. Cleaning of the equipment is the main issue concerning food safety within this process step.
Food safety issues: Cross-contamination through the equipment.
A large part of the blood present in the body is being released and captured, the other part remains in the body (e.g. hart, liver, veins). Effective capture of blood is a point of interest at this stage; therefore the recapture-reservoir for blood should be long enough (animal must be fully bleed till death) and the blood reservoir should be cleaned and disinfected after every processing day.
Food safety issues: Soiling of the environment and therefore spreading of the pathogens.
Halal slaughter (Muslim)
To be qualified as “halal”, the meat must come from an animal slaughtered by a Muslim, who cuts the throat of the animal so that it bleeds to death, faced towards Mecca. At present chickens are stunned in this process, which affects animal welfare and hygienic processing in a positive way, since excessive wing flapping is avoided. The slaughterer must also offer the prayer “Bismilla Rahim wa Allah Akbar” (In the name of Allah, Allah is great). In all European countries, the killing of animals for meat consumption is regulated by many laws and decrees that aim at protecting the consumer -and his health- and the animal from suffering. In practice, a mechanical or an electric shock can cause heart fibrillation e.g kills the animals. But special dispensations are granted to slaughterhouses that cater for the Jewish and Muslim communities.
This raises technical problems: since the animal dies by bleeding, it slows down the production of the slaughterhouse (two men can slaughter ritually between 1.000 and 2.000 chickens each hour, instead of 6.000 when the neck cut is applied automatically). In 1980 a decree was passed ruling that animals can be ritually slaughtered only by people “qualified by registered religious organisations”, and that such organisations must be “registered by the Ministry of Agriculture”.