Omphalitis in Day-Old Chicks (Navel Ill / Yolk Sac Infection)
Hatchery manual covering Escherichia coli, Salmonella, and Enterococcus etiology, unclosed navels, foul yolk sac necrosis, and incubator sanitation.
Scientific Overview
Omphalitis (Navel Ill / Mushy Chick Disease) is an infectious, non-contagious inflammation of the navel and yolk sac in day-old chicks. Triggered by bacterial entry into unclosed or poorly healed navels immediately after hatching, it is a primary cause of early chick mortality during the first 7 days of brooding.
Etiology & Hatchery Pathogenesis
Omphalitis is defined as a bacterial infection of the unhealed umbilical tissue, predominantly caused by opportunists like E. coli, Proteus, Enterococcus, and Pseudomonas.
Infection occurs in setters, hatchers, or chick transport boxes when bacterial contaminants colonize moist, unclosed navels, migrating rapidly to infect the nutrient-rich yolk sac.
Necropsy Lesions & First-Week Mortality Peak
Pathognomonic signs and necropsy findings:
- Mushy, Soft Abdomen: Affected chicks are lethargic with distended, discolored abdomens and wet, scabbed navels.
- Foul Unabsorbed Yolk Sac: Necropsy reveals enlarged yolk sac containing watery, foul-smelling yellow-green exudate or curd-like caseous yolk.
- Mortality Curve: Mortality spikes sharply between Day 3 and Day 5 post-hatch, dropping off by Day 7-10.
Hatchery Sanitation & Humidity Control
Since established yolk sac infection is non-treatable, prevention is critical. Maintain egg sanitation before setting, ensure correct setter/hatcher relative humidity (50-60%) to promote rapid navel closure, and sanitize hatcher baskets between hatches.
All scientific data, diagnostic criteria, and performance benchmarks presented on this page are derived from published peer-reviewed journals and official veterinary codes:
- Avian Pathology & Diagnostics: World Organisation for Animal Health (WOAH, 2023). Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Paris, France.
- Poultry Diseases & Histology: Swayne, D.E., et al. (2020). Diseases of Poultry (14th ed.). Wiley-Blackwell / American Association of Avian Pathologists.
- Nutrition & Feed Chemistry: Leeson, S. & Summers, J.D. (2001). Commercial Poultry Nutrition (3rd ed.). University Books, Guelph, Ontario.
- Commercial Breed Standards: Aviagen (2024). Ross 308 & Cobb 500 Broiler Performance Objectives. / Lohmann Breeders (2024). Lohmann Brown Management Guide.