18 Jan 2021

Exploring possible origins of scratch lesions in broilers

lesiones en la piel de los pollos

Content available in: Español (Spanish)

With the arrival of spring-summer, there is usually an increase in chickens with skin lesions that arrive to the processing plant. In the poultry sector, affected birds are often referred to as scratched or stripped, and are caused by the clawing of the dorsal and sometimes ventro-lateral or posterior parts of the abdomen.

These lesions have a direct impact on the physical integrity of the bird and therefore cause a significant economical loss of the carcass value. They are the cause of subcutaneous infections known as cellulitis, in which subcutaneous connective tissue get accumulated with fibropurulent material, leading to the seizing of carcasses of affected birds at the processing plants. Considering these birds arrive to the plants with this injury, then the problems must be sought in the phases of farming and/or transport. In the initial analysis of this incidence, it is essential to distinguish whether the skin wounds are:

  • Old – occurred throughout the growing process.
  • Recent – occurred during loading and unloading.

However, it must be taken into account that there are other factors within the slaughter process that can; either individually or in combination, aggravate the skin wounds and make them more visible, such as:

  • Flocks with poor uniformity
  • Scalding temperature
  • Plucking process

This article will review the possible causes behind these lesions and the consequent loss of quality of the carcasses. As many of the problems we face today in poultry farming, their origin is usually multi-factorial and therefore a holistic approach is necessary to understand the problem and apply corrective measures.


There is a clear relationship between high densities and increased scratch marks. When the birds try to access the feeders, they tend to crowd each other. More birds imply heavier crowding, leading to more frequent physical contact and consequently, hurting each other. In relation to density, it is especially important to spread the birds around without any delay, to avoid crowding and reduce nervousness in the chickens.

In the same house, it’s important to avoid spots where the density of birds is higher. The following situations can be the origin of migrations:

  • In installations with tunnel type ventilation, birds tend to migrate towards cooler areas or with higher air speeds (especially in summer).
  • In the houses where pen-separating nets are used during rearing, the birds tend to stay in these areas even as they grow (out of habit), thus leading to higher densities.
  • The feeders act as sieves. If the feed has excess fines, they will fall on the first troughs of the circuit. Chickens tend to move towards the end of the house, where the granulation of feed in the feeders is more desirable.




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