The ratio of hens to roosters in a breeder flock and the causes of mortality during the production period.

Ratio of hens to roosters
In broiler breeder flocks, the optimal hen-to-rooster ratio for achieving the highest fertility and hatchability rates is typically 8 to 10 hens per rooster (1:8 to 1:10).
A lower ratio (e.g., 1:6) leads to intense competition among roosters and causes stress in the flock.
A higher ratio (e.g., 1:12 or above) reduces the number of successful matings, ultimately resulting in decreased fertility and lower hatchability performance.
This ratio is set slightly higher at the beginning of the production period (24–30 weeks of age) because rooster fertility declines over time, and maintaining flock balance becomes necessary.
Causes of mortality in breeder flocks during the laying period
Mortality during the production period (24 to 60 weeks of age) can vary between 8% and 12% and is mainly caused by the following factors:
Diseases
Viral diseases: Infectious bronchitis, Newcastle disease, avian influenza.
Bacterial diseases: Colibacillosis, Salmonellosis.
Parasitic diseases: Coccidiosis, lice, and mites.
Vaccination management and hygiene are among the most important preventive measures.
Nutritional problems
An imbalanced diet (deficiency of vitamins, minerals, or essential amino acids) can lead to weakened immune system, reduced fertility, and increased mortality.
Stress-related mortality
Transport, overcrowding, sudden temperature changes, and loud noises cause stress-related mortality.
Leg and skeletal problems
Excessive weight in roosters or hens can cause leg problems, lameness, and forced culling of birds.
Reproductive disorders
Flock conflicts (such as pecking and rooster fights), testicular problems in roosters, and ovarian or egg binding in hens are causes of reduced production and increased mortality.
Poor quality of roosters
Poor quality of day-old male chicks (low weight, abnormalities, or genetic weakness) leads to reduced reproductive lifespan and increased early culling.
Strategies to reduce mortality
Strict health management (complete vaccination, disinfection, and control of animal traffic).
Proper nutrition tailored to age and production stage.
Maintaining appropriate stocking density and adequate ventilation.
Replacement or addition of young roosters during the mid-weeks to maintain fertility.
Training personnel to manage stress-inducing behaviors in the flock.
Conclusion
Maintaining the correct hen-to-rooster ratio and comprehensive management of health, nutrition, and stress are among the most important measures to reduce mortality and improve fertility and production performance in breeder flocks.
Standard table of hen-to-rooster ratio and expected fertility percentage.

Management tips related to ratio and fertility:
At the beginning of production, roosters are usually kept in slightly higher numbers (ratio of 8:1) because fertility is high in the first months and rooster conflicts occur less frequently.
With increasing age, rooster fertility declines; consequently, the hen-to-rooster ratio should gradually increase to prevent intense competition and stress.
Rejuvenation of roosters (replacing some older roosters with younger ones) can improve fertility during the final weeks.
Maintaining the health of roosters’ feet and weight is essential, as skeletal abnormalities or excessive weight reduce the frequency of successful matings.