Heat stress in chickens: signs, prevention and what to do on a hot day

Heat is one of the biggest risks in poultry keeping across much of Africa. Chickens have no sweat glands and are covered in insulating feathers, so they struggle to lose heat. Fast-growing broilers and high-producing layers generate a lot of body heat and are especially vulnerable. When the air around them gets too hot, birds eat less, grow more slowly, lay fewer and thinner-shelled eggs and, in severe cases, die. Losses can be heavy in a single afternoon, particularly in heavy broilers close to slaughter weight.

How hot is too hot?

Adult chickens are generally most comfortable at around 18 to 24 °C. As the temperature rises above the high 20s, they start to feel the heat. Above about 30 °C most birds pant, and above about 35 °C, especially with high humidity, the risk of death rises sharply. Humidity matters because panting works by evaporating water; in humid air, it cools the bird less.

Signs of heat stress

• Panting with the beak open.
• Wings held away from the body.
• Birds lying flat, sometimes with legs stretched out, or crowding at walls, doors or the coolest side of the house.
• Less feed eaten and more water drunk.
• Pale combs and wattles, and lethargy or collapse in severe cases.
• In layers, fewer eggs, smaller eggs and thin or soft shells.

Housing: prevention starts with the building

Good housing does most of the work. Many of these measures cost little, especially if they are built in from the start.

• Orientation: in the tropics, the long axis of the house should run roughly east to west, so the sun shines mostly on the roof and short end walls.
• Roof: a reflective or light-coloured roof, insulation under iron sheeting, or a whitewashed roof reduces heat coming in. A generous roof overhang shades the walls.
• Height and openings: higher roofs and open sides with wire mesh and curtains let hot air escape and breezes through. Close curtains only as needed for cold or wind.
• Shade around the house: trees and shade cloth, placed so they do not block airflow.
• Ventilation: in larger houses, fans that move air over the birds help a lot; evaporative cooling pads are used in commercial houses where humidity is low enough for them to work.

Stocking density

Crowded birds cannot lose heat, and each bird adds its own body heat to the house. In hot seasons, place fewer birds per square metre than in cool seasons. For broilers, this matters most in the last weeks before slaughter when birds are heaviest. Ask your chick supplier or extension officer for density guidelines suited to your housing and climate.

Water: the most important tool

Birds drink much more in hot weather, often around double what they drink in cool weather. If they cannot get enough water, heat stress kills quickly.

• Add extra drinkers in hot weather so that every bird can drink without competing.
• Keep water as cool as possible: shade tanks and pipes, bury supply pipes, and flush lines in the afternoon so birds get fresh, cooler water.
• Keep drinkers clean and check every day that they are working.
• Electrolytes and vitamin C are sometimes added to water during heat waves. Use products made for poultry and follow the label or your vet's advice.

Feeding and daily management

• Feed in the cooler hours: early morning and evening. Digesting feed produces heat, so birds that eat during the hottest part of the day heat up more.
• For broilers, some farmers remove feed for a few hours over the hottest part of the day, while keeping water available at all times.
• Avoid handling, catching, moving, vaccinating or transporting birds in the heat of the day. Do it early in the morning or at night.
• Keep litter dry and not too deep; wet litter raises humidity in the house.
• Watch birds closely during heatwaves, especially in the afternoon, and act at the first signs of panting.

Choosing birds for hot areas

Indigenous and village chickens found across Africa are generally more heat-tolerant than commercial broilers and layers, though they grow and lay less. Some local and improved dual-purpose strains carry the naked neck trait, which reduces feather cover and helps them shed heat. For backyard and free-range systems in hot areas, these birds can be a sensible choice. For commercial production, the solutions lie mostly in housing and management.

Key points

• Chickens suffer above the high 20s °C and are at serious risk above about 35 °C, more so in humid heat.
• Well-oriented, shaded, ventilated housing is the foundation.
• Reduce stocking density in hot seasons.
• Plenty of cool, clean water is the most important protection.
• Feed and handle birds in cool hours, and watch closely during heatwaves.
• Talk to your vet or poultry adviser about a heat plan for your farm.