Heat is produced by essential bodily processes (metabolism) which include maintenance, growth and egg production. Heat production is affected by body weight, species and breed, level of production, level of feed intake, feed quality and, to a an extent, by the amount of activity and exercise.
Heat is generated when there is an increase in temperature may be as a result of artificial heat supply  or lack of adequate ventilation in the poultry house.

Temperature is the degree of hotness or coldness of a body at a given time. The internal body  temperature of birds(41°C)  generally ought to be normal at all times to avoid heat stress.

Heat stress is a condition in chickens (and other poultry) caused by high temperatures, especially when combined with high relative humidity and low air speed. Some factors that can cause heat stress  include genetics, feather cover, acclimation to heat, drinking water.  Older birds, heavy breeds, and broilers are typically more susceptible to heat stress.

Severe heat stress can cause drops in production efficiency and increased mortality rates in your flock. You may notice reduced growth rates, egg production, and hatching rates. Heat stress can also cause a change in egg quality. You may notice smaller eggs, thinner shells and overall poor internal egg quality.

Signs of heat stress in birds

When the normal temperature range(18-24°) of a poultry house is increased, heat stress may certainly occur and there are some abnormal signs your birds may exhibit when they are undergoing heat stress and these signs include;

Ø Low feed intake (between 26-32°C)

Ø Hard breathing, panting (35°C)

Ø Prostration and death (38°C)

Ways to combat heat stress in birds

1.  Make sure your flock has access to clean, cool water at all times! This is very important!

Supplement lost electrolytes.

Heat stress can reduce the chicken’s body of electrolytes. A water-soluble electrolyte powder can be used during times of heat stress to help replenish electrolytes that have been lost. Be sure to follow the manufacturer’s instructions on the package when using electrolytes. Electrolytes also increase your bird’s water intake, which is definitely a good thing when trying to help them cool off.

2.  Provide protection from the sun. Shade, misters, and even wading pools are a welcome relief from the heat.

3.  Avoid over-crowding;  Your poultry need space to move away from the body heat of other birds.

4.  Feed during the cooler times of the day. Digestion generates heat and birds will be less likely to eat during the hotter parts of the day.

5.  Keep your birds calm. Don’t let children, dogs or other pets chase or disturb your flock.

6.  Maintain good and hygienic environment for your birds;  poultry debris can generate heat which can create room for heat stress.