Occurrence: Worldwide. Species affected: Broilers. Age affected: Young fast growing.

Causes: A deformity of the 6th thoracic vertebra which causes spinal cord compression and posteria paralysis. Influenced by conformation and growth rate. Non-infectious, it is aggravated by fast body development.

Effects: Incidence of affected birds may reach 2% of the flock. Peak incidence occurs at 3-6 weeks of age. Severely affected birds may become laterally recumbent (lay on their sides) and may die from dehydration if not culled. Lordosis (curving forward) and subclinical spondylolisthesis are common in broilers and develop soon after hatching.

Young and fast growing broilers are susceptible to this chronic disease. It is a development disorder influenced by confirmation and growth rate, resulting in a deformity of the 6th thoracic vertebra, which caused spinal cord compression and posterior paralysis.

It is a non-infectious metabolic disease of broilers, aggravated by fast body development. It does not occur in breeders, where growth rate is slowed by restricted feeding. It can be increased by genetic selection.

It is one of many skeletal problems caused by rapid growth rate in broilers.

The incidence of affected birds may reach 2% of the flock. Peak incidence occurs at 3-6 weeks of age

Severely affected birds often become laterally recumbent (lay on their sides) and may die from dehydration if not culled.

Lordosis (curving forward) and subclinical spondylolisthesis are common in broilers and develop soon after hatching.

The posterior paralysis results from rotation of the body of the 6th vertebra along the axis of the spine with the posterior part of the body moving dorsal (backward) and anterior (forward), relative to the anterior part.

The rotation causes a kyphotic (humpback) angulation of the floor of the spinal canal between the 6th and 7th thoracic vertebrae and spinal cord compression. The deformation of the spinal column can be readily recognised by palpating the ventral surface of the spinal column during necropsy.

Spondylolisthesis is best confirmed by removing, decalcifying and splitting the spinal column along a midline longitudinal plant to allow visualisation of the spinal cord compression.

It simulates other developmental skeletal disorders such as valgus (twisted outward) and various deformation of the intertarsal joint, tibial dyschondroplasia, osteochondrosis, degenerative joint disease and osteoporosis.

A twisted spinal column resulting in a definitive diagnosis can be seen without decalcifying in extreme cases.

Slowing growth rate as is done in breeders (by restriction of light or feed), and genetic selection of birds that are less susceptible is helpful.

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