Enterococci and BCO lameness in broilers (femoral head necrosis)
BCO is an increasingly common cause of lameness in fast-growing broilers. Gut bacteria — among them Enterococcus cecorum — cross into the blood and settle in the growth ends of the bone, destroying the femoral head. We explain how to spot the problem, what drives it and how to cut the risk through gut health, water quality and a strong chick start.
verifiedFrom the team that has organised work on poultry farms for years.
Lameness in broilers has many causes, but one is drawing particular attention today: BCO, bacterial chondronecrosis with osteomyelitis. It is not a classic, textbook entity — the problem has grown in recent years alongside ever faster bird growth. The mechanism is indirect: bacteria living in the gut cross into the bloodstream, circulate around the body and settle where bone is still growing — in the cartilaginous growth ends of the femur and tibia. There they trigger necrosis and inflammation, and the bird starts to limp.
Where do the bacteria in the bone come from?
The gut is the key. In a fast-growing broiler the gut barrier can be under strain — with feed stress, wet litter or poorer water quality it lets bacteria into the blood more easily. Enterococcus cecorum keeps recurring among them, but staphylococci, streptococci, E. coli and other microbes can cause BCO too. Once in the blood they reach the fastest-growing parts of the skeleton, where the blood vessels form natural ’traps’. A focus of necrosis forms in the femoral head, the cartilage separates from the bone, and in some birds it ends in a fracture and a complete inability to walk. That is why preventing BCO is mainly about caring for a healthy gut and a clean environment, not just treating symptoms.
The picture of BCO in a flock
BCO is hard to confirm without a post-mortem, but the typical flock picture and an awareness of the risk factors let you react early and limit losses.
Lameness at 3–6 weeks
BCO usually shows in the second half of the rearing period, when birds are already heavy and the bone is growing fast. Single lame broilers appear and increasingly sit down over time. This time window is characteristic and sets BCO apart from lameness in the first days of life.
Birds sitting and reluctant to move
A sick bird spares the painful leg: it sits on its hocks, is reluctant to stand, limps when forced to move, sometimes rests on the hock joint. Poorer access to feed and water deepens the problem, and the bird falls behind the flock.
Changes visible only at post-mortem
A firm diagnosis of BCO only comes from examining the skeleton of dead or culled birds. In the femoral head you see a focus of necrosis, separating cartilage, sometimes purulent exudate. This examination is best left to a vet, who will confirm the cause and point out what to look for next.
Fast growth and body weight
The faster the bird grows, the greater the load on young, still cartilaginous bone, and the easier it is for micro-damage to form where bacteria settle. Very intense growth curves in the first weeks are one of the strongest risk factors for BCO.
Gut stress and wet litter
Anything that damages the gut barrier raises the risk: sudden feed changes, dysbiosis, diarrhoea, wet and caked litter. Damp litter means both higher bacterial pressure in the environment and a greater chance that microbes cross from the gut into the blood.
Chick quality and water quality
A weak start — poorer-quality chicks with a mishandled first day — gives birds more prone to infection. Water is similar: a contaminated drinking system and biofilm in the lines are a constant source of bacteria. Clean, good-quality water and an even, strong start are the foundation of prevention.
BCO prevention step by step
- 1
Give chicks a strong start
The first day shapes resilience for many weeks. Provide the right temperature, fast access to feed and water and a calm placement. The more even and stronger the start, the better the gut works and the less prone the bird is to bacteria crossing into the blood.
- 2
Look after gut health
A stable, healthy gut is the best barrier against BCO. Avoid abrupt feed changes, respond to diarrhoea and dysbiosis, and support a proper microflora in line with your vet’s advice. The less gut stress, the fewer bacteria reach the bloodstream.
- 3
Keep litter dry
Dry, friable litter lowers bacterial pressure in the house and supports leg health. Control humidity, ventilation and the tightness of the drinking lines so you don’t soak the floor. Wet, caked spots are hotbeds where microbes multiply.
- 4
Care for water quality and acidification
Clean water and a clean drinking system limit a constant source of bacteria. Wash and disinfect the lines regularly, remove biofilm, and apply water acidification in line with your vet’s advice — a lower pH limits the multiplication of many microbes in the system. It is a simple, everyday lever for prevention.
- 5
Don’t force growth too hard
A very intense growth rate in the first weeks loads young bone. The feeding programme and growth curve are worth discussing with your vet and nutrition adviser, so that birds grow strongly but without overloading a still cartilaginous skeleton.
- 6
Encourage birds to move
Active birds have stronger legs. An even spread of feed and water, good lighting and platforms or enrichment encourage the flock to walk. Movement strengthens the bones and helps you spot early the birds that are starting to limp.
Frequently asked questions about BCO lameness in broilers
What exactly is BCO?add
BCO is bacterial chondronecrosis with osteomyelitis — damage to the bone growth ends caused by bacteria that crossed from the gut into the blood and settled in the fastest-growing parts of the skeleton. It most often affects the femoral head and the upper end of the tibia. The result is necrosis of cartilage and bone and, in the bird, lameness that in more severe cases ends in a fracture and an inability to walk.
What is the role of Enterococcus cecorum?add
Enterococcus cecorum is one of the most frequently named bacteria in BCO cases in broilers, but not the only one. Staphylococci, streptococci, E. coli and other gut microbes can cause it too. They share a common route: from the gut to the blood, and from there to the growing bone. That is why prevention focuses on gut health and reducing bacterial pressure, not on one specific germ.
Can BCO be cured with an antibiotic?add
Once there is a focus of necrosis in the bone, an antibiotic alone rarely reverses the changes in affected birds, and any treatment is always carried out under a vet’s supervision and with the withdrawal period observed. It is far more effective to limit new cases through prevention: a strong start, a healthy gut, dry litter and clean water. BCO is a problem that is easier to prevent than to treat.
Why is BCO appearing only now?add
It is a relatively fresh, growing topic you won’t find in older poultry disease matrices. The rise is linked mainly to ever faster broiler growth — young, still cartilaginous bone is under more load and more prone to the micro-damage where bacteria settle. Add environmental factors such as water quality, litter condition and gut health, and BCO is treated today as a management challenge rather than a single, simple disease.
Keep a flock health record in DlaFerm.pl
In DlaFerm.pl you note lameness observations, keep a treatment and withdrawal-period log and run a digital flock card — all in one place, ready for a conversation with your vet. Create a free account or write to us.
Phone
+48 796 258 151