A broiler in week four looks big and healthy, and in the morning it’s lying on its back with no sign of disease. Others sit and won’t get up to the feeder. The frustrating part is that the best birds — the fastest growers — die most often. It isn’t an infection but the price of speed: heart, lungs and bones don’t always keep up with the muscle.
Sudden death syndrome
The bird dies within a minute: it flaps its wings, flips onto its back and dies. Most often it’s cockerels at 2–4 weeks, often at night or when startled. The cause is a heart rhythm disturbance in a fast-growing bird.
What lowers the risk:
- at least 4–6 hours of continuous darkness at night from week one;
- not pushing growth in the first two or three weeks: a moderate start, then catch-up;
- not startling birds at night with sudden light or noise.
Ascites
The belly swells and goes soft, the comb turns bluish, the bird breathes heavily. The heart can’t cope with the load, and fluid collects in the abdomen. Ascites is more common in the cold, with poor ventilation and at high altitude — anywhere birds are short of oxygen.
Good ventilation helps (on house climate), as does an even temperature without chilling and, as with sudden death, moderate early growth.
Legs
| What you see | Possible cause |
|---|---|
| Legs splay or bow outward | Growth too fast, slippery floor, lack of manganese or choline |
| Soft bones, a bendable beak | Rickets: not enough calcium, phosphorus or vitamin D |
| Bird sits and is reluctant to stand | Joint overload, dyschondroplasia, joint infection |
| Dark scabs on the footpads | Wet litter — pododermatitis |
If many birds go lame at once, call the vet: there are infectious causes too.
What reduces losses
- Light with darkness. Round-the-clock light gives more gain early on, but also more leg and heart problems. In many countries a dark period for broilers is required by law.
- Dry litter. Wet litter damages feet and joints (on bedding).
- Feed by age. Starter, grower and finisher are different feeds. Homemade mixes more often end up unbalanced in minerals.
- Stocking density. In crowded houses birds move less and legs weaken.
- Culling. A broiler that can’t reach water will die anyway. Better to cull it at once than leave it suffering.
What mortality is normal
A good flock loses 3–5% over the whole cycle. If sudden death and legs account for more, the rearing program needs to change. Limits of normal and when to call the vet are in poultry mortality rates.
Mortality day by day
Log mortality in EggPulse every day, and note in the inspection what you saw: “sudden,” “legs,” “ascites.” Over a few flocks you’ll see which week the losses start and whether changes to light and feed helped. And weekly weighing will show whether the flock is growing too fast.
