Bacterial chondronecrosis with osteomyelitis (BCO), also called femoral head necrosis (FHN), is a serious bacterial infection affecting the growth plates of the leg bones in Cornish cross (broiler) chickens. It is a common problem in commercial poultry worldwide and represents a major welfare concern. The disease causes inflammation, severe pain, stress, lameness, and prevents affected birds from accessing food and water.
Cornish cross chickens are genetically selected for extremely rapid and disproportionate growth. This puts excessive strain on their bones. The long chondrocyte columns in the proximal growth plates of the femur and tibia are particularly vulnerable.
Excessive mechanical stress can cause microfractures in the cartilage, including damage to blood vessels, which reduces blood flow. These damaged growth plates provide an entry point for opportunistic bacteria from the bloodstream—often originating from the gut or respiratory tract. The combination of mechanical stress, impaired blood flow, and bacterial infection leads to necrotic lesions characteristic of BCO.
Staphylococcus spp is the most frequent bacteria involved but
Escherichia coli, and
Enterococcus spp. have also been reported.
Clinical Signs
The hallmark symptom of BCO is
lameness, which may present as:
- Limping
- “Wing walking” (using wings to support the body)
- Abnormal gait
- Complete inability to walk
Affected birds spend most of their time on the ground and may hesitate to move. In severe cases, they cannot reach feed or water, leading to dehydration and starvation.
BCO Lesion Severity Scoring
The poultry industry uses a 0–3 scale to assess BCO lesion severity in both femoral head necrosis (FHN) and tibial head necrosis (THN):
- 0 : Normal; no abnormalities in proximal femur or tibia
- 1: Proximal femoral head separation (epiphyseolysis) and mild THN
- 2: Proximal femoral head transitional degeneration and severe THN
- 3: Proximal FHN with caseous THN
Risk Factors
Key factors that increase BCO risk include:
- Prolonged sitting and inactivity: Restricts blood flow to femora and tibiae, causing ischemia in growth plates.
- Rapid growth: Excessive mechanical stress on the thick cartilage layers of femora, tibiae, and thoracic vertebrae.
- Wire flooring: Creates unstable walking surfaces and increases foot lesions.
Prevention Strategies
- Probiotics: Supplement diets prior to onset of lameness to reduce pathogenic bacteria, improve gut health, and boost immunity.
- Housing considerations: Minimize inclines or slopes; repeated climbing increases BCO risk threefold. Do not use wire flooring.
- Encourage Exercise: Use treat balls or slow feeders to keep birds active.
- Stress reduction: Minimize exposure to stressful conditions.
