There is no single mortality percentage that is safe to ignore in every broiler flock. Age, cause, timing and speed matter. One sudden cluster of deaths can require faster action than a larger number spread across a long cycle.
Contact a veterinarian or animal-health authority when mortality rises suddenly, several birds show severe respiratory or neurological signs, or avian influenza or another reportable disease is suspected. Do not move or sell sick birds.
Calculate mortality and survival
Mortality percentage = birds dead or culled ÷ birds placed × 100.
Survival percentage = birds alive ÷ birds placed × 100.
Record daily deaths and removals separately. Cumulative mortality alone can hide a dangerous daily spike.
What should farmers monitor?
| Record | Why it matters |
|---|---|
| Date and bird age | Shows when the problem began |
| Deaths and culls | Separates natural deaths from removals |
| Location in house | May reveal heat, airflow or equipment patterns |
| Feed and water change | Can provide early warning |
| Signs and lesions | Supports professional investigation |
| Action taken | Creates an auditable flock record |
Common causes by production stage
- Early chicks: poor chick quality, dehydration, chilling, overheating, starvation, yolk-sac infection or brooder hazards.
- Growing broilers: coccidiosis, enteric disease, ventilation failure, heat stress, wet litter, feed or water problems.
- Heavy birds: heat stress, leg problems, ascites, sudden death syndrome, feed withdrawal or handling losses.
These are investigation categories, not diagnoses. Necropsy and laboratory testing may be needed.
When mortality becomes an emergency
- Deaths increase sharply above the flock’s normal daily pattern.
- Many birds become sick at the same time.
- There are respiratory signs, swollen heads, blue combs, paralysis or severe diarrhoea.
- Feed, water or egg production falls suddenly.
- Poisoning, heat failure or contaminated feed is possible.
The World Organisation for Animal Health notes that highly pathogenic avian influenza can cause rapid and severe flock mortality. Follow Nigerian veterinary reporting instructions for suspected cases.
Do not treat the percentage alone
Antibiotics do not treat viral disease and should not be used routinely without diagnosis. Remove obvious environmental hazards, secure samples where a professional instructs, isolate movement and obtain veterinary help.
Financial effect
Each dead bird has already consumed chicks, feed, heat, labour and health inputs. Report mortality beside FCR, average sale weight and cost per surviving bird.
Use the Mortality and Survival Tracker for daily calculations and the Cost Calculator to measure the financial effect.
Prevention
- Buy traceable chicks.
- Prepare brooder heat, water and feed before arrival.
- Maintain biosecurity and dry litter.
- Follow a veterinary vaccination plan.
- Monitor water, feed, temperature and ventilation daily.
- Investigate unusual deaths early.
See the Poultry Biosecurity Guide.
Final guidance
Use mortality percentage as a monitoring signal, not a permission to ignore deaths below a fixed threshold. Timing, clinical signs and sudden change determine urgency.
