Managing Heat Stress in Poultry Production

Poultry Farming in Summer is an important topic to understand because heat stress causes adverse effects on the performance of poultry production. The summer season causes several harmful effects on broilers and layers, which ultimately reduces profitability. Heat stress is a severe concern for poultry producers as it directly leads to financial losses by impaired poultry performance.

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.

Due to the common occurrence of environmental stressors worldwide, many studies have investigated the detrimental effects of heat stress on poultry production. It has been seen that heat stress negatively affects the welfare and productivity of broilers and laying hens. Understanding and controlling heat stress in poultry is crucial to successful poultry production and profitability.  

Heat stress is one of the most critical environmental stressors challenging poultry production worldwide. The detrimental effects of heat stress on broilers and laying hens range from reduced growth, decreased egg production, egg quality, and safety. Moreover, the negative impact of heat stress on poultry welfare has recently attracted increasing public awareness and concern.  

What Happens in Heat Stress in Birds?

Birds become heat stressed between body heat loss and body heat production, the average body temperature of poultry is 410 c. When the environmental temperature exceeds 350c. A bird is likely to experience heat stress. In effect, to maintain body temperature, birds first rely on losing heat from blood vessels near the surface of the skin by a process called non-evaporative cooling.  

However, this mechanism is only effective when the ambient temperature is lower than the bird’s body temperature. As ambient temperature increases beyond the bird’s thermoneutral zone, non-evaporative cooling becomes ineffective. At these higher temperatures, the bird relies on panting/evaporative cooling to control body temperature. Panting is an effective but energy-expensive way for the bird to regulate body temperature. It typically results in lower feed intake and growth and reduced feed efficiency.

It will also increase water intake to offset water loss. Still, the situation is complicated because the body’s ability to retain water is reduced as the evaporative cooling process escalates. During high ambient temperatures, the birds increase panting up to 10 times from an average rate of 25 breathes/min to 250 breathes/min, which leads to an excessive loss of carbon dioxide resulting in raised blood plasma bicarbonate levels and increased blood ph.  

The bird attempts to correct blood ph. by excreting bicarbonates via urine. Bicarbonates are negatively charged ions coupled with positively charged ions such as potassium to be passed in the urine. However, as potassium is essential in maintaining intracellular water balance, a loss of potassium ions via urine reduces the ability to maintain this water balance. Consequently, while birds compensate for water losses associated with panting by consuming more water, their retention in the body cells is limited by simultaneous loss of electrolytes such as potassium in the urine.  

According to Marne’ Meyer at Novatek, hot season is the most challenging month for broiler farmers in particular because of the increase in the heat and humidity since most farmers do not have temperature-controlled housing. However, she advises that farmers try and implement the following to ensure maximum production regardless of a less favourable environment.

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. Insulation 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 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.

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