First Week Mortality: 
This may be due to incubation faults, such as excess humidity in the final stages of incubation resulting in pot bellies and unhealed navels. Faulty brooding arrangements and infections, like omphalitis, can also lead to high mortality rates. In such cases, dead chicks may have unabsorbed yolk in their bellies.

Second Week Mortality: 
Mortality during the second week is mostly due to bacterial infections contracted at birth or immediately after placement.

Third Week Mortality: 
Mortality due to viral infections and feed deficiencies begins after the third week. Viral infections, such as New Castle, Gumboro, and Infectious Bronchitis, can cause severe mortality. Diseases like Coryza and Chronic Respiratory Diseases are commonly observed after the third week.