As part of poultry processing, birds must be thoroughly plucked, and all feathers must be removed, including those that are most firmly attached. The most common approach to achieving this is to include scalders as part of plucking operations to loosen the head and wing feathers. These scalders also will loosen the leg cuticle.

There are ways, however, that this process can be carried out along the overhead conveyor. 

It is worth remembering that, to achieve a well-plucked bird, several aspects prior to plucking need to be carried out well, including:

  • Waiting time of the live birds at the processing plant
  • Hanging on the overhead conveyor
  • Stunning
  • Slaughter and bleeding
  • Scalding

These stages of the operation are worth considering in detail as they can all influence the success of the plucking operations.

Plucking needs to be viewed as the removal of feathers without, for example, ripping the skin, the emergence of bones through the skin, or the excessive accumulation of blood due to the application of too much pressure. 

Waiting in the reception area

Birds should be kept in comfortable conditions. In hot climates, heat stress needs to be prevented. Should birds overheat, they will pant and this results in an excessive accumulation of blood in the legs and wings.

Hanging on the overhead conveyor

Birds must be properly held. Use only three fingers - the thumb, index and ring fingers. When placing onto the shackles, hold by the legs, not the thighs, to prevent possible bruising and blood accumulation. While moving birds from the cages to the shackles, flapping must be minimized. Installation of a breast comforter is also recommended. 

Excessive flapping at this stage of the process can result in an excessive accumulation of blood in the wings that cannot be drained during bleeding, and in internal and external damage to the bird. 

Stunning

To help keep birds as calm as possible while being transported from the hanging area to the stunner entrance, a tunnel made from a dark plastic sheet could be erected. Passage through this will calm the birds. 

However, even with this in place, various precautions need to be taken to prevent pre-stun problems. For example, wing flapping results in knocks to the wings, either as a result of contact with hard structures or other birds, and this can lead to bruising that can extend over the entire wing surface. When birds flap their wings excessively, they tend to raise their necks, and this can mean that they do not enter the stun bath and so remain conscious. 

Slaughter and bleeding

Stunning leads to a lack of consciousness and lowering of the heartbeat to 350 beats per minute. This lowered heartbeat will stay low for only 10-12 seconds. It is also important to remember that the various parameters of the stunning bath must be adjusted to the average weight of the bird, for example, frequency, voltage and bath height. Some birds will be subjected to excessive current and, in some cases, wings can become dislocated. 

Scalding

As with stunning, all the variables of the scalder must be taken into proper consideration, for example, time, temperature, total immersion and water agitation.

If carcasses are not fully submerged during their movement through the scalder, the most firmly attached feathers, i.e. those of the tail and the neck, will not enter the water. Consequently, their follicles will not properly dilate and the feathers will not be loosened. 

Additionally, if the water level in the tank does not ensure that the shackles are submerged to a depth of at least three inches, those feathers close to the leg joints and the cuticle will not be loosened. It is also worth keeping in mind that for this to be successfully achieved, water needs to be of a sufficiently high temperature. 

Scalding raises the carcass temperature, and it is worth trying to retain this heat during passage from the scalder to the plucker.

Challenges of feather removal

Given all of the above, it is worth considering the challenges faced by plucking operations on a daily basis. 

These would include removal of feathers leaving the epidermis or dermis intact, depending on whether the bird is yellow or white, respectively. 

Additionally, it should be noted that plucking is based on average carcass weight, therefore automatic removal of each and every feather from all birds is not possible. Because of this, there will always be the need for at least one worker to remove some of the remaining feathers, for example from the head and the tail.

The temperature of the scalder is lower than needed to remove some feathers, for example head feathers. This is to avoid over-scalding the breast, which would impact on the quality and yield of the processed bird. 

And so arises the question: It is possible to pluck birds and keep costs low and quality and yield high, while they remain on the overhead conveyor? 

This can be achieved, if the following are implemented. 

Heat and water

Carcasses must be kept warm. Warm water (34-36C) should be used during plucking and any heat that has been absorbed from the scalder must be preserved throughout the plucking process. This can be achieved but installing a structure that prevents heat loss during passage from the scalder to the plucker.

Strategically place hot water (70-75C) sprayers along the approach to the plucker. These should be directed towards the head and thigh joint and spray water for approximately six seconds.

Plucking technological advances

Advances in plucking machine technology mean that various types of equipment can now be used in combination, for example:

  • Equipment that can adjust automatically to the anatomy of the bird
  • Equipment that rotates counterclockwise
  • Equipment that can be placed inside moving cabinets, i.e. if the cabinet or structure itself moves, all the plucking units move with it

Remember also that in the selection of plucking fingers, three types should be used - soft, semi-hard and hard. They must be carefully positioned to ensure that they remove feathers without damaging skin.

Depending on the sequential efficiency of the plucking operations, some plucking lines should be avoided to prevent dislocated or broken wings, skin and breast scratches, blood accumulation in the tips and other areas of the wings.

If the above is followed in a disciplined manner, it is possible to reduce the damage to chickens during plucking and so reduce operational costs.