Broilers grow best between 18 and 21 °C, and heat stress begins above about 25 °C, according to a 2020 review. In Riyadh the average daily maximum is 43.7 °C in July and August, and in Amman it is 32.4 °C in August. For most of the summer, a broiler house in the region is fighting the weather.
What heat does to the flock
A bird cannot sweat. It pants, eats less and moves less, and the cost shows up in the numbers. In one experiment cited in a widely used review, birds under chronic heat stress ate 16.4% less, weighed 32.6% less at 42 days and needed 25.6% more feed per kilogram of gain. Mortality rises on top of that, often in a single hot afternoon when a fan or a pad fails.
Older, heavier birds suffer first. A 2026 study from ILVO and Ghent University, based on more than 4,000 observations, found that a 2.5 kg broiler’s breathing rate starts climbing at 26.6 °C inside the house, and that heavier birds react at lower temperatures still. The last week before slaughter, when the birds are worth most, is when the house is most at risk.
Why temperature alone misleads
Birds lose heat by panting, which works only if the air can take up their moisture. That is why researchers measure heat load with a temperature-humidity index rather than the thermometer alone.
Evaporative cooling pads with tunnel ventilation are the standard answer in hot climates, and they work: one modelling study found pads cut house temperature by about 3 °C once it passed 25 °C. But pads also push relative humidity above 70%, which makes panting less effective. A house can read 30 °C and still be stressing the birds. Controlling the pads and fans on temperature alone misses this.
What sensor-led control changes
The fix is to measure what the birds feel and let the controller act on it. That means temperature and humidity sensors at bird height in several zones of the house, not one probe near the door, and a controller that uses both readings to decide fan stages and pad timing.
Early field results are encouraging. In a preliminary trial of a ventilation algorithm based on the house’s heat balance, the improved control lowered daytime temperature by 1.5 to 2 °C and cut mortality by 16.5% compared with the existing controller. It was one rearing period in two houses, so the result needs confirming, but the direction is clear.
Two cheaper signals add a lot. Water meters per house show when birds drink less, often an early sign of disease. Alarms that reach the farm manager’s phone when power, a fan bank or the pads fail turn a lost night into a short repair.
How to start
- Log temperature and humidity at bird height in three or four places for one summer week, and compare the readings with what the controller sees.
- Check that fan capacity, pad area and air speed match the house size and the birds’ weight at the end of the cycle.
- Install alarms for power, fans and water before investing in advanced software.
How Zoonexa helps
Zoonexa assesses your houses in summer conditions, recommends the climate sensors, controller settings and alarms that fit your buildings, installs them and trains your team to read the data. See our housing, climate and feeding solutions or book a farm visit before next summer.