Key maintenance points in the poultry processing plant

Ensuring the proper functioning of key operations during poultry processing is essential to maintain yield and output.

Misaligned shackles can increase the risks of carcasses being damaged. (Eduardo Cervantes Lopez)
Misaligned shackles can increase the risks of carcasses being damaged. (Eduardo Cervantes Lopez)

A failure to properly maintain and adjust the equipment commonly used in the poultry processing plant can have a significant impact on a plant’s yield and output.

Certain equipment is key to the quality and quantity of birds produced and so merits particular attention. Staff responsible for management at these critical points need to not only ensure optimal functioning, but also understand why proper functioning is so important.

Take, for example, the fans that may be used primarily to keep employees cool. While they need to keep workers cool, they must also be as quiet as possible. Noisy fans will cause birds stress, resulting in more blood being pumped into the legs and wings, and this may impact a successful bleed and ultimately final product.

Overhead conveyor and shackles

Shackles must be properly connected to the conveyor to ensure that, as birds are raised or lowered, they remain vertical. This is particularly important when considering operations such as scalding, to ensure that backlogs of chickens do not occur either on entry to the scalder or at exit.

Backlogs can also occur if shackles are mounted too close to each other, impeding the proper movement of carcasses.

For similar reasons, shackles must always be straight. Over time, they may become misaligned and, should this happen, when birds pass through the plucking machines, for example, the risks increase that they will be damaged so reducing quality, and possibly leading to rejects.

Similarly, issues may arise should shackles be missing. A carcass hung next to an empty space, with consequently greater space to swing, will be at more risk of damage to the legs, thighs, breast and wings as it passes through the plucker. In some cases, a missing shackle can result in birds exiting the plucker in pieces, leading to a total loss of product.

A failure to ensure proper tension in the overhead conveyor can cause a buildup of birds, similarly risking the integrity of carcasses.

Breast comforter

The breast comforter must be securely mounted to prevent the any vibrations or shaking each time a broiler is hung onto the shackles. Should movement occur, birds will not remain calm during transport to the stunner, flapping their wings and raising their heads.

The breast comforter must be correctly aligned so as to only come into contact with the bird’s breast. When hung on the shackles, gravity forces a bird’s intestines to come into contact with the vagus nerve. On stimulating this nerve, the breast comforter returns the bird to a state of calm, hence the importance that contact is concentrated on this area.

The surface of the comforter must be as smooth as possible but rigid, with the aim of guaranteeing contact.

The breast massager must be present throughout passage to the stunner entrance and this route should be covered with a plastic sheet or metal structure forming a tunnel and shielding birds from the rest of the plant.

Missing Breast Comforter 2

The benefits of the breast comforter will be lost of sections of it are missing. (Eduardo Cervantes Lopez)


Birds’ heads should enter the water of the stun bath, so enabling the current to pass through the brain, continue through the soft tissues and exit via the legs.

However, this may not occur should the birds experience pre-shock, caused by their wings or breasts touching an improperly grounded entrance ramp. Should this occur, the birds will panic, flapping their wings and raising heads, and will exit the stunner without being stunned.

This state of panic can also harm the birds externally and internally. Their wings may be damaged, and, within their breasts, bleeds can occur should blood vessels break. This can be a greater problem when larger birds are processed.

When birds exit the stunner, they pass through two phases: the tonic, during which they shake, and the clonic, during which birds are completely relaxed prior to reaching the manual or automatic killer.

A failure to understand these two phases can lead to staff thinking that birds have not been properly stunned and increasing the voltage the amperage. This, however, can lead to hemorrhagic leg syndrome and, in some more extreme cases, the fragile bones of the thorax breaking, resulting in bleeds. 

The impact of the tonic phase can be reduced by simply installing a breast comforter at the exit of the stunner.


Carcasses must be properly bled prior to entering the scalder and bleed time must reflect the season, climatic conditions and the plant’s height above sea level.

Birds must be completely dead before entering the scalder. Should this not be the case, then carcasses will exit the scalder with a reddish color.

Staff at scalding operations must ensure that the carcasses are fully submerged while in the scalder. Should they float, the tail and wing feathers, which are the only ones that spring from muscles and so can be harder to remove, will not be properly loosened.

It is also important that water turbulence within the scalder is continuous and even to ensure that feathers and properly lifted, allowing water to reach the follicles.


The heat that accumulates in carcasses must be preserved if good feather removal is to be achieved. If it is not, the pluckers will need to be adjusted. However, this brings with it a number of risks.

Any remaining fecal matter in the carcass will emerge and be spread over the skin. As most of the feathers will have been removed, the follicles with be open and empty, allowing this fecal matter to enter the skin, and the pressure of the plucking fingers may lodge it there, making removal extremely difficult.

Additionally, the extra pressure of the plucking fingers may tear those areas where the skin is thin, or even result in the dislocation of wing bones.


How to ensure quality, speed during broiler harvesting

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