Bacterial chondronecrosis with osteomyelitis (BCO), also known as femoral head necrosis (FHN), is a serious bacterial infection of the growth plates in the leg bones of Cornish cross chicken breeds (broilers). It occurs commonly in the commercial poultry industry worldwide. The disease is a major welfare issue, as the infection results in inflammation, severe pain, stress, lameness, and inability for the birds to reach food and water.
BCO occurs as a result of the translocation of opportunistic bacteria across the intestinal and respiratory epithelial barriers. Onset of lameness is attributable to osteomyelitis within the physis and metaphysis of rapidly growing proximal tibiae. The bacteria most commonly isolated from infections include
Staphylococcus aureus, but
Escherichia coli, coagulase-negative staphylococci and
Enterococcus spp. are sometimes involved, as are, rarely, other bacteria.
BCO Lesion Severity Scoring
A scoring scheme was developed to assess the severity of BCO lesions (both femoral head necrosis (FHN) lesions and tibial head necrosis (THN) lesions), on a scale of 0 to 3.
- 0 : Normal; There are no abnormalities of the proximal femoral head or proximal tibia.
- 1: Proximal femoral head separation (epiphyseolysis) and mild proximal THN.
- 2: Proximal femoral head transitional degeneration and severe tibial head necrosis.
- 3: Proximal FHN and caseous THN.
BCO Risk Factors
- Prolonged sitting and inactivity: When birds remain in a sitting position for long periods of time, it can restrict blood flow from the major arteries to the femora and tibiae, leading to ischemia in the growth plates.
- Rapid growth: Rapid growth of the bird imposes excessive mechanical force on the thick cartilage layers of proximal femora, tibiae, and thoracic vertebrae.
- Use of wire flooring: It increases the risk of foot lesions on the bottom of their feet and creates an unstable walking surface which puts additional stress on their bones.
Prevention of BCO
- Administer Probiotics: Supplementing the diet with probiotics has been proven to reduce incidences of the disease. They work by attenuating intestinal populations of pathogenic bacteria, by improving gut health and integrity and enhancement of the immune system. The probiotics must be administered prior to onset of BCO lameness.
- Maintain a flat environment: Keep the ground as flat as possible. Minimize any inclines or slopes which require birds to have to climb up. When cornish breeds were housed in an environment where they had to repeatedly walk up and down slopes, the risk for BCO increases 3-fold.
- Encourage Exercise: Treat balls and slow feeders are useful tools for encouraging activity in cornish breeds.
