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Heat stress is one of the most important causes of economic losses of companies in the poultry sector in tropical climates and has a great impact on productivity and mortality.
In normal environmental conditions, birds maintain their balance with the environment, however, by altering the temperature, birds will have to compensate for these variations above or below their thermal comfort zone.
Heat stress begins when the ambient temperature rises from 26.7 ° C and potentializes above 29.4 ° C.
When the birds begin to pant, physiological changes have already begun in the body to dissipate excess heat; before the birds reach this point, anything that can be done to help the birds stay comfortable will help keep growth, hatchability, egg size, shell quality, and production in peak condition.
Table 1. Expresses the different physiological events in birds as the environmental temperature varies.
The ideal range of ambient temperature for birds is between 18 and 24 ° C and the neutral between 13 and 24 ° C; Temperatures above or below will force birds to turn on their thermoregulation mechanism to compensate for these variations.
Birds are very sensitive to heat outbreaks, and cannot endure extreme temperatures for long; this is because they cannot sweat as they don’t have sweat glands. Additionally, they are covered with feathers, making it difficult for them to dissipate the heat that is generated inside their body and that which comes from outside.
Layers can suffer more than other birds, since most of the facilities on today’s farms are automatic or generally housed in cages.
Chickens in cages are totally dependent on the proper functioning of ventilation equipment to dissipate heat from their bodies.
With genetic changes, and types of facilities and cages, chickens have lost resistance to extreme heat.
As the bird’s body temperature increases, feed consumption, growth, feeding efficiency, viability, and quality of the eggshell decrease; This is particularly severe when the ambient temperature rises extremely, since the possibility of losing heat by non-evaporative means (loss of heat through the skin) is significantly reduced.
The internal temperature of adult birds is around 40 ° C – 41.66 ° C, if said internal temperature reaches 43.3 ° C – 45.6 ° C, the birds are in danger of death.
Adult birds resist cold much better than heat, as their internal temperature can drop to 23.9 ° C ...
