An investigation on first-week mortality in layers

Area of Science:

• Poultry Science
• Animal Health
• Veterinary Pathology

Background:

• Day-old chick placement and management critically influence first-week mortality (FWM) and layer welfare.
• High FWM rates indicate potential issues in early life management and health.

Purpose of the Study:

• To investigate the causes and impact of FWM in commercial layer flocks.
• To identify key pathogens and risk factors associated with FWM.
• To establish a predictive model for total rearing mortality based on FWM.

Main Methods:

• Post-mortem examination of 983 chickens from 50 layer flocks.
• Bacterial pathogen identification (Escherichia coli, Enterococcus faecalis).
• Statistical analysis of FWM correlations with total mortality and flock uniformity.
• Genetic characterization of identified bacterial pathogens.

Main Results:

• Infectious causes accounted for 50% of FWM; non-infectious causes included dehydration and visceral gout.
• Escherichia coli and Enterococcus faecalis were the primary bacterial pathogens linked to FWM.
• A significant correlation was found between FWM and total rearing mortality, enabling predictive modeling.
• No significant correlation was observed between FWM and flock uniformity at 1-2 weeks or 15 weeks of age.
• Genetic analysis indicated a polyclonal nature of infections, suggesting multiple infection sources.

Conclusions:

• Minimizing FWM to below 1% is crucial for improving overall flock health and reducing total mortality.
• Effective early management and biosecurity are essential to control E. coli and E. faecalis infections.
• FWM serves as a valuable indicator for predicting and managing rearing period mortality.