Ventilation and heat stress in Pakistani summers
A broiler has no sweat glands and wears a down jacket. Above about 30°C it stops growing to stay alive — and in much of Pakistan that is five months of the year.
Awaiting veterinary review. This guide is written from published industry practice and has not yet been checked by our domain advisor. Confirm anything clinical with your own veterinarian before acting on it.
Summer is the single largest recurring cost in Pakistani broiler production, and it is charged in three ways: mortality on the worst days, lost growth on every day, and a feed conversion that quietly worsens all season.
Why heat hurts a broiler specifically
A chicken cannot sweat. It loses heat by panting, which costs energy and water, and it is covered in feathers that were selected to keep it warm.
Worse, the modern broiler has been selected for fast growth, and fast growth generates metabolic heat. The bigger and faster-growing the bird, the less heat it can shed. A 2 kg broiler in week 5 is far more vulnerable than a chick.
The comfort zone for a grown broiler is roughly 18–24°C. Above about 30°C the bird begins actively reducing feed intake to reduce its own heat production. Karachi, Multan, Rahim Yar Khan and much of Sindh spend months above that.
Humidity changes everything
Panting works by evaporating water from the respiratory tract. When the air is already saturated, evaporation slows and panting stops working.
38°C in dry Multan air and 38°C in humid Karachi air are not the same stress. Coastal humidity is why Sindh loses birds at temperatures that inland farms tolerate.
This is also why evaporative cooling pads work far better inland than on the coast. A pad system adds moisture to the air; in already-humid conditions that can make things worse rather than better.
What the bird shows you, in order
- Wings held away from the body
- Panting, beak open
- Reduced feed intake, sharply increased water intake
- Birds moving to the coolest part of the shed and crowding
- Lethargy, pale comb
- Collapse
By stage 4 you are already losing performance. Stage 6 is minutes from death, and piling — birds crowding into a corner and smothering each other — kills more birds on a bad day than the heat itself.
Open house: what you can actually do
Most Pakistani sheds are open-sided, and the options are limited but real:
- Roof insulation. The highest-return change most open sheds can make. A bare metal roof radiates heat down onto the birds all afternoon.
- Fans that move air across the birds. Air movement removes heat even when the air is not cool.
- Roof sprinklers. Wetting the roof, not the birds.
- Cut stocking density in summer. Fewer birds means less heat produced and more floor per bird. This is the intervention farms resist most and it is one of the most effective.
- Feed at night. Move the main feeding to the cool hours. Digestion itself produces heat, so feeding at 2pm in June works against you.
- Cool, clean, abundant water. Intake can roughly double in heat. If the water line runs across a hot roof, the water arriving at the bird is warm and it will drink less of it.
Controlled sheds
A tunnel-ventilated shed with evaporative cooling is the real answer, and it is why controlled housing has spread across Punjab. It also introduces a new failure mode: a controlled shed in a power cut is more dangerous than an open shed, because still air and closed sides are exactly the wrong combination.
If you run controlled housing, the backup generator is not optional equipment. It is the thing standing between you and losing a shed in twenty minutes.
The cost you never see on a bad day
Farms count heat mortality. Almost nobody counts the rest: a flock that spent the summer eating less grows slower, reaches target weight later, and eats more feed per kilogram while it does. That bill is larger than the dead birds.