In Zambia, October is the most chal- lenging month for broiler farmers as the heat and humidity increases drastically. Since the majority of farms in Zambia do not have temperature-controlled housing, the chickens are exposed to the environmental factors and subsequently leads to a drop in broiler growth and production. However, there are measurements that can be taken by the farmer to reduce the impact of heat stress and ensure maximum production in a less favourable environment.

Heat stress is a physiological state in which the body heat production is greater than the body heat loss of the bird. The bird starts to pant in an attempt to reduce body temperature, but as the environmental temperature increases beyond the upper critical temperature the bird enters heat stress. During the summer season it is important to be vigilant of the bird’s behavior in order to identify heat stress and prevent any loss as soon as possible. Broilers will move away from other birds to reduce heat, lift their wings away from their bodies, consume less feed, increase water consumption and start to pant.

Broiler farmers can do the following to reduce the impact of heat stress:

Correct house design

The first step to successful broiler is to ensure proper infrastructure. The broiler house should be constructed on an east-west axis to ensure minimum direct sunlight into the house. The roof of the house should be high enough to increase ventilation. Insultation is a great investment as it will be beneficial both in the summer, to reduce heat and in the winter to prevent heat loss from the house. Another practical tip is to paint the roof white or with a reflective paint to prevent environmental heat from penetrating into the house.

Reduce stocking density

Metabolic heat is produced when a bird consumes feed that is metabolized into nutrients that are used for maintenance and production. As the growth rate increases, the metabolic heat production increases, creating a hot micro-climate inside the broiler house. By reducing the stocking density, the heat in the house will be reduced and the birds will also have more space to spread out and reduce their body temperature. Reducing the stocking density will also allow birds easier access to feed and water.

Reduce water temperature

Water and feed intake have a direct relationship in broilers as chickens consume approximately two milliliters of water for every one gram of feed consumed. Thus, if water intake is restricted, feed intake will be affected. Reducing the temperature of the water will greatly impact water intake. Just imagine drinking an ice-cold glass of water on a hot day! There are many methods to reduce the water temperature such as adding ice to the water and ensuring proper insulation of the water tank.

Feed a well-balanced diet

During heat stress birds tend to reduce their feed intake in an attempt to reduce the amount of metabolic heat produced and this will directly affect growth rates. The general rule is that feed intake will be reduced by three point six percent for every one degree Celsius above twenty-seven degree Celsius. Feeding a well-balanced diet with easily digestible ingredients will thus ensure a smaller impact on growth rates and production. Although the farmer is not capable of controlling the environmental temperature, he is able to reduce the impact thereof on his business through the above management practices.

As environmental temperatures increase, management becomes critical.

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