Each and every day, billions of broilers are transported from the farm to the processing plant. However, when it comes to hanging birds on the overhead conveyor, how many are condemned as a result of death from heat stress? These condemned birds not only reduce the volume produced at the plant but also the cost per kilo of meat.

To minimize the problems caused by heat stress, it is worth keeping in mind that chickens have a number of natural mechanism to reduce body heat. These include:

  • Lying down and a reduction in movement
  • Opening their wings and raising feathers
  • Avoiding food, as digestion produces heat, thus increasing the body temperature
  • Panting, which increases heat evaporation, thus reducing body temperature slightly

Additionally, heat is released from the body into the atmosphere through: 

Radiation  – heat that radiates from warmer to cooler areas 

Convection  – the transfer of heat through airflow, for example, resulting from fans 

Conduction  – via the blood stream (in warmer temperatures, blood moves toward the extremities allowing a faster diffusion of heat)

Evaporation  – through the skin and the respiratory tract via panting

Minimizing environmental discomfort

When birds are harvested, they are moved from a relatively comfortable space where they can exhibit natural behavior into cages, which restrict behavior, in order to be transported to the processing plant. 

The only natural mechanism available against rising temperatures once inside the cage is evaporation. However, to keep birds cool, a number of various measures can be taken. 

Cages of birds are commonly stacked up to five high while waiting to be moved on to the truck. To help reduce heat, cage stacks should be orientated to make the most of airflow, with a minimum space between each stack of 5 (preferably 10) centimeters, so that air can freely circulate. 

Encouraging this airflow will help to cool birds’ necks and heads, where the wattle and comb function much like the radiator of a car. If, however, there is insufficient air circulation, birds will lay with their beaks open, indicating that they are suffering from heat stress. 

During transport 

In addition to ensuring an adequate air supply in and around stacks of cages, the trucks used to transport birds to the slaughter house can de redesigned to increase comfort. When this is done successfully, there is no panting and open beaks are not observed. Various options can help to raise comfort levels. 

Trucks often have a metal sheet welded to the platform behind the cab where the full cages are stacked. This serves to protect the platform from fecal matter, which can be highly corrosive and damage this part of the vehicle. However, this sheet can also be harmful to the birds, especially to those are in the center of the load and toward the bottom, because they receive almost no ventilation. 

This metal sheet should be completely removed. If steps to prevent corrosion are to be taken, then this can be achieved through use of a plastic sheet, which facilitates better airflow and that can be easily washed on a daily basis. 

Additionally, inserting plastic spacing tubes between cages of birds can increase lateral airflow while trucks are traveling, while the addition of a canopy over the cages can protect birds from direct sunlight during their journey.

At the plant 

After weighing trucks at the plant, they should be immediately washed. As well as maintaining them in a clean state, this will also help to reduce the fecal load before birds enter the scalder. 

Once unloaded, birds should be immediately placed in the storage area as close as possible to the handling area. This should be air conditioned to help ensure that birds are kept at the right temperature.
Once the chickens arrive at the plant, the airflow that kept them cool during their journey from the farm is significantly reduced, and evaporative heat can increase. Because of this, the ventilation perimeter between the cages should be increased to aid heat dissipation. 

Some plants also have air-conditioned sheds where trucks can be parked, and this helps to prevent the buildup of heat.

Achieving the above, however, remains a challenge for many. 

Yet some companies are working with trucks that can achieve the unloading of large numbers of birds in under two minutes, with the goal of storing cages in the waiting area as quickly as possible. Working with high volumes in short periods may, however, require some degree of plant redesign. 

An additional advantage of this approach is that the sooner trucks are emptied, the sooner they can back on the road and bring more birds to the plant.

So it worth remembering that the only business to benefit from failing to tackle evaporative heat is the rendering business, and that’s not the objective of the processing plant!