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Poultry production guide – Part 6: The correct steps in the slaughtering process

A few steps need to be taken to get the chicken from the farm onto your plate. This process can make some people uncomfortable.

The good news is that in modern abattoirs the utmost care is taken to ensure that the poultry is despatched in the most humane way possible, without causing the animals any undue stress. The following will guide you through the process step by step, to aid you in planning your own poultry abattoir.

The process consists of several phases. The first is transport and receiving facilities for live birds. Second, the birds then need to enter the production line where the next steps of stunning, scalding, defeathering and evisceration will take place.

After this, the poultry can be portioned, packaged, and kept in cold storage for distribution to the retail market.

Receiving live birds

This part of the process starts on the farm. It is important to choose the abattoir closest to your farm to limit transport costs, and to limit the stress that the transport may cause the birds. Stress can have a negative impact on the quality of the product, as well as causing mortalities while in transit. Birds that are dead on arrival will be discarded for hygienic reasons, and can therefore lead to a loss of income for the farmer.

The abattoir must have a roofed receiving area where the crates can be unloaded. Gates are essential to ensure that access to the facility can be controlled with strict bio-security measures in place.

The production line

After the birds have been received, they are attached to the production line. This is done by attaching their feet to the conveyor and hanging them upside down. The live poultry receiving and stunning areas must have dimmed lighting. One minute must be allowed between the hanging and stunning point. Approximately 15 to 18 birds per minute per handler are permitted. Hangers hanging the birds must treat them in a humane and calm way. Birds must be hung facing the same direction. Both legs must be secured into the shackles. A guide rail is usually provided, which will relax the birds. Bends in the slaughtering line should be kept to a minimum, and any disturbing obstructions should be removed. Supervision is important.

Stunning

An alternating current of 60 or 110 mA is required for small and large chickens respectively. The current should only go through the head and specifications for the equipment must be followed. Line speed must allow for 4 to 7 seconds contact time (dwell time) within the stunning apparatus. Eleven to fifteen seconds is allowed from stunning to throat slitting. A saline solution can be used to increase the conductivity of the water and make stunning more effective. Total recovery time after stunning should not exceed 2 minutes. Constant maintenance must be done on the equipment. All birds must be stunned before being bled. The ideal voltage for electrical stunning is debatable, but as a guideline, voltages between 50 V and 70 V should be adequate for wet stunning if the head and neck of a bird is immersed in the electrified bath.

Bleeding

The bird should bleed for at least 90 seconds. Respiration must stop and the bird must be dead before entering the scalding tank. This will prevent water in the scalding tanks from entering the lungs and air sacs and contaminating the carcass. More than 80% of the blood is lost within 40 seconds of slaughter. Thorough bleeding results in a lifeless, non-struggling carcass before immersion and soaking takes place. A sharp knife or blade must be used for this purpose and it must be sterilised frequently.

The process of scalding

Soaking in hot water softens the skin and feathers, thus facilitating the defeathering process. Standard “hard” or “hot” scalding is done at ± 54 °C to 60 °C for 2 to 2,5 minutes. The epidermis is removed providing for a whiter looking carcass.

Standard “soft” or “cold” scalding is done at ± 50 °C to 53 °C for 3,0 to 3,5 minutes. The scalding process wets the feathers and warms the skin thus releasing some of the muscle pressure of the skin holding the feathers. The whole carcass must be immersed. A constant inflow of clean water at the right temperature is necessary to keep all carcasses totally submerged at all times and to control the build-up of micro-organisms.

When the level is too low the “sock” feathers will not be scalded resulting in incomplete defeathering of the hocks. Agitation of the scalding water is important for thorough penetration onto the skin and preventing “cold spots” in the scalding tank. A chlorinated water spray, after hot water immersion and just before defeathering, is recommended in order to decrease micro-organisms.

The process of defeathering

Defeathering takes place after soaking. A defeathering machine consists of a round metal disc with grooved (corrugated) rubber fingers spinning on either side as well as below the hanging bird. The softness/ hardness of the rubber fingers and the regular replacement of damaged fingers are  important for proper defeathering.

The rubber plucker fingers are colour coded for the different grades of hardness. By placing the plucking machines in series, excessive loss of carcass temperature is prevented. Water used in the defeathering machines should not exceed 20 °C to prevent any further damage to the epidermis.

The quantity of water in the plucker should be between 0,25 to 0,50 litres per bird. The nozzles of the sprayers should be directed in such a way that they easily wash away all the feathers on the plucker discs and inside walls of the plucker machine. In the smaller abattoirs, various different models of defeathering equipment are used. They can differ in size from 1 to 10 birds at a time.

Maintenance and performance checks on defeathering machines are very important. A trained supervisor for this department is important. This person must understand the importance of setting the height, angle and distance between the plucker banks.

Evisceration process

During this process, the defeathered carcasses are attached to a different production line. Here, the heads and feet will be removed, as well as the internal organs and the crop. Once the carcass has been through this process, it can be either packaged as a whole chicken and moved to cold storage, or the carcass can be divided into portions before it moves on to packaging.

The information used in this article is credited to the Meat Inspectors Manual, published in 2017 by the Directorate: Veterinary Services Veterinary Public Health National Department Of Agriculture Republic Of South Africa. For more information visit their website www.nda.agric.za.

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