How to manage rubber finger use during poultry processing

Defeathering is reliant on the successful management of rubber fingers, and there are variety of factors that can contribute to their performance.

Each and every disc must have its full complement of plucking fingers as missing fingers will affect the quality of defeathering and lead to those fingers in place wearing our more quickly. (Eduardo Cervantes López)
Each and every disc must have its full complement of plucking fingers as missing fingers will affect the quality of defeathering and lead to those fingers in place wearing our more quickly.  (Eduardo Cervantes López)

Rubber fingers play a key role in poultry processing, but there are various factors that can impact whether they produce a well-plucked bird or not. Their monitoring is essential to ensure not only a well-defeathered carcass but also that fingers are not worn or damaged or that good fingers are wasted.

Natural rubber is preferable for fingers, and their firmness and positioning must correspond to the type of feathers to be removed. The pressure needed to remove feathers varies. For example, wing and tail feathers spring directly from muscle making them more difficult to remove.

Part of the process

All equipment must be properly aligned and in good working order if the fingers are to perform at their best.

For example, overhead conveyors must run smoothly without pauses as small interruptions can result in the birds swinging. When swinging birds pass through the plucking machines there will be additional friction, and this may not only damage the skin of the broilers but will result in additional wear to the fingers.

Every shackle must be filled. Should there be gaps, the chickens passing through the stun bath will receive more current resulting in greater muscle contraction. To counter this, in some plants, the temperature of the scalders is increased and plucking machines are slightly more closed. This results in more friction and, consequently, the fingers have a shorter working life. Additionally, there will be an increase in the number of carcasses rejected due to skin damage.

If the entrance to the stun bath is not properly maintained birds may suffer pre-shock, putting them into a state of high alert. Their national reaction is to raise their heads and intensely flap their wings, and they may pass over the bath without being stunned. Many plants opt to increase the voltage when they see that birds are leaving the bath conscious; however, this results in greater muscle contraction in those that are stunned, resulting the problems mentioned above.

A characteristic of a successfully stunned broiler is that, on exit from the stun bath, it will be shaking before completely relaxing. Should an operator fail to understand this, he or she may increase the current in the belief that the bird has not been properly stunned. This leads to greater muscle contraction, which is good neither for the broiler nor the rubber fingers.

Bleed time will depend on local conditions. In cold climates and in plants over 1,000 meters above sea level, vasoconstriction will occur, and blood will be more viscous. This requires a longer bleed time, of up to 3.5 minutes, to ensure proper blood removal and that there is no leakage during evisceration.

Plants that operate hard scalding use higher water temperatures, but broilers remain for less time in the scald tanks. However, when birds enter the plucking machines at high temperatures there is an impact on the plucking fingers. The heat of the bird, in addition the friction that occurs as the bird passes through the plucking machine, can accelerate the rubber’s crystallization and breakage.

Adjustment and correction

The plucking machines must be properly adjusted if they are to perform at their best. Should they be too closed birds will be forced backwards, and this leads to them being exposed to fingers for longer, wearing down the fingers and potentially damaging the carcass skin. Costs will rise not only due to the number of rejected birds but also because of the additional wear to the fingers.


Plucking fingers must not come into contact with the shackles. (Eduardo Cervantes LĂłpez)

Shackles move along parallel guides and, if these guides are too close, the shackles may become stuck. If too loose the shackles will shake which can lead to poor contact with the plucking fingers. The plucking fingers should never touch the shackles and a distance of 0.5 to 1 cm should be ensured.

Even in the best managed plants, the daily contact between fingers and carcasses will lead to wear of the fingers’ extremities which can compromise quality; the importance of regular inspection cannot be overlooked.

Fingers need to be checked everyday to ensure that they have not become worn, are not split, have no missing ends or are otherwise damaged due to movement. To ensure that defeathering is carried out well, the machines must have all their discs in full working order, and the correct fingers must be in place on each and every disc.

Some plants only replace missing fingers at the end of each week. Mixing new and old fingers, however, can lead to a variety of problems, including that they wear out more quickly and that the pluck is uneven.


Failure to properly adjust the plucking machines will result in fingers wearing out quicker and raise replacement costs. (Eduardo Cervantes LĂłpez)




Page 1 of 34
Next Page