Easy guide to BCO lameness in chickens: Causes and solutions

Non-infectious lameness includes conditions like dyschondroplasia (abnormal bone growth), rickets (weak bones due to calcium or vitamin D deficiencies), fractures, and poor nutrition (e.g., lack of choline or biotin). Infectious lameness, on the other hand, is caused by microorganisms like bacteria, but not only and this makes it a very difficult problem to tackle.

One major type of infectious lameness is Bacterial Chondronecrosis with Osteomyelitis (BCO)—a complex condition that stands out as the leading cause of lameness in broilers globally.

What is BCO?

BCO is a bacterial infection that affects the bones and joints, particularly those under mechanical stress, such as the femur, tibia, and thoracic vertebrae. These areas are most vulnerable in fast-growing broilers, especially young birds with fragile skeletons.

BCO is widespread, impacting about 1 in every 67 broilers over 30 days of age under normal circumstances. During outbreaks, over 15% of a flock may be affected. In Europe, up to 30% of broilers suffer from painful leg disorders caused by BCO and related skeletal issues, creating both welfare and economic challenges.

BCO is often aggravated by secondary factors, such as rickets, caused by imbalances in calcium, phosphorus, or vitamin D levels. Poor nutrition, chronic gut inflammation, and the destruction of fat-soluble vitamins increase susceptibility. These factors weaken bone development and create ideal conditions for bacterial invasion.

But where do the bacteria come from?

The bacteria responsible for BCO, such as Enterococcus spp., Escherichia coli, and Staphylococcus spp., originate in the gut.

In fast-growing broilers, mechanical stress on bones leads to cartilage damage and inflammation. Damaged areas attract bacteria, which travel from the gut into the bloodstream and settle in joints, multiplying and causing infection.

Young birds are particularly vulnerable because their microbiome is still not established. An immature microbiome and an immature gut tissue makes it easier for harmful bacteria to colonise and consequently transfer into the blood stream.

In some cases, bacteria may also be transmitted vertically from parent stock to chicks.

Challenges in treating BCO

Treating BCO is difficult, every practitioner can confirm that, and it is due to several factors:

Limited blood flow to cartilage: Bone cartilage has minimal blood supply, making it hard for antibiotics to reach infected areas effectively. Disruption of gut microbiome by antibiotics: While antibiotics can kill harmful bacteria, they also disrupt the gut’s natural balance, delaying the development of beneficial bacteria and leaving room for pathogens to take over. Rapid growth and immature microbiomes: The quick growth of broilers lead to mechanical stress on bones and joints. Simultaneously, their immature intestinal tract and microbiomes heighten their vulnerability to bacterial infections.

Preventing and managing BCO

The best approach to combat BCO is prevention, focusing on reducing bacterial load, stabilising the gut microbiome, improving intestinal health, and supporting bone and cartilage health. If we really want to have success in preventing BCO, the focus has to be on all of this points.

• Early gut health stabilisationEarly colonisation of the intestinal tract with the right bacteria is crucial.
• Nutritional supportIncluding butyric acid in feed strengthens the gut lining, improves resilience, and enhances overall digestive health. Scientific literature has proven many times, that butyric acid is paramount for the health of the intestinal tract, when delivered at the right place.
• Strong bone developmentA balanced diet with adequate calcium, phosphorus, and vitamin D is essential for healthy bone growth and strength. Research shows that using 1,25(OH)₂D₃ (the active form of vitamin D) can reduce lameness by over 50%. When supplemented during the first four weeks of life, 1,25(OH)₂D₃ strengthens the skeleton and even the immune system.
• Environmental managementProper ventilation and litter management help prevent wet bedding, which can harbour bacteria.
• Avoid overuse of antibioticsWhile antibiotics may seem like a quick fix, they can delay microbiome development and increase susceptibility in the long run. Preventing bacterial translocation (movement from the gut to the bloodstream) is more effective than relying solely on antibiotics.
• Strengthen the gut barrierCombining butyrate, medium-chain fatty acids, plant extracts, essential oils, and monolaurin can significantly strengthen the gut lining. These supplements support microbiome balance, reduce pathogen spread, and improve overall gut health.

Key takeaways for BCO prevention

• Focus on gut health: Early microbiome stabilisation reduces harmful pathogens and prevents bacteria from entering the bloodstream.
• Support bone strength: Proper nutrition and vitamin D supplementation help reduce microfractures in bones.
• Minimise mechanical stress: Slower, steady growth reduces pressure on joints and bones.
• Use targeted supplements: Fatty acids, essential oils, and butyrate strengthen the gut lining and reduce pathogen spread, while 1,25(OH)₂D₃ (the active form of vitamin D) will strengthen the structural bones and cartilage resistance.

By implementing these strategies, broiler farmers can significantly reduce the prevalence of BCO, improve bird welfare, and enhance overall productivity. Better gut health and the wright vitamin D supply leads to stronger cartilage and bones, fewer microfractures, and less bacterial spread—ultimately resulting in healthier chickens and fewer cases of BCO.