Occurrence: Increasing more common in fasting growing meat type birds due to a metabolic disturbance and in breeder pullets due to a bacterial infection. The incidence of affected birds may reach 2% of the flock.
Species affected: Broilers and broiler breeders.
Age affected: Young fast growing broilers at 5 to 8 weeks of age and breeder pullets from 10 to 18 weeks of age.
Causes: In broilers it is a developmental disorder influenced by conformation and growth rate and in breeder pullets it is due to a bacterial infection.
Kinky Back (spondylolisthesis)
It is a disorder influenced by conformation and growth rate, resulting in a deformity of the 6th thoracic vertebra, which causes spinal cord compression and posterior paralysis. In boilers it is due to a developmental disorder influenced by fast growth rate, whereas in breeder pullets it is caused by a bacterium.