HEAL ▶▶▶TH
Examining heat stress in poultry
Poultry and humans have similar preferences when it comes to temperature, researchers have found. A study by the Technical University of Munich (TUM), Germany, found that cattle, pigs and even agricultural crops, also favoured the same temperature range.
BY TONY MCDOUGAL T
he comfortable temperature range for poultry is 15- 20°C (59-68°F) with birds experiencing mild heat strain at 30°C (86°F). At 37°C (98°F) and above, chick- ens experience severe heat stress and their egg lay-
ing rate declines. When people are exposed to temperatures above 32°C (90°F) at extremely high humidity, or above 45°C (113°F) at very low humidity for a lengthy period of time, it can be fatal.
Lower performance Heat stress overall leads to reduced growth in chickens, cat- tle, dairy cows, pigs and other livestock, which means both lower yields and reproductive performance: “There are exam- ples of evolutionary adaptations to warm weather in terres- trial mammals. Transylvanian naked chickens are more heat tolerant than other varieties of chickens because of a com- plex genetic mutation that suppresses feather growth. They are naturally air-conditioned because they lack feathers,” says Professor Senthold Asseng, professor of digital agriculture at TUM.
Climate change Professor Asseng believes that climate change could cause in- tense problems for humans, poultry and other livestock and crops by 2100: “By the end of the century, 45-70% of the global land area could be affected by climate conditions in which humans cannot survive without technological support, such as air conditioning. Currently, it’s 12%. ... This means that in the future, 44-75% of the human population will be chroni- cally subjected to stress caused by heat. A similar increase in heat stress is expected for livestock, poultry, agricultural crops and other living organisms.”
Mitigating heat strain Professor Asseng advocates a variety of strategies to mitigate growing heat strain, including increasing the amount of natu- ral shade from trees or buildings. Cities and buildings can be made more temperature-passive by using roof and wall insu- lation or by using lighter, more reflective roof and wall col- ours to reduce heat strain. Despite the genetic adaptation of the Transylvanian chickens, it takes many generations to achieve. “The time available is too short for many higher life forms. If current climate trends persist, many living things could be severely affected or even disappear completely from the Earth due to temperature change,” he concludes.
Heat stress leads to a multitude of problems in chickens. Mitigating stress with water misting is one way to reduce the drop in productivity.
20 ▶ POULTRY WORLD | No. 7, 2021 The review was published in The Lancet Planetary Health.
PHOTO: KOOS GROENEWOLD
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