Diet as an external factor in the expression of scoliosis in a line of susceptible chickens.

An inbred line of chickens that develops severe scoliosis, an isogenic line and a line of birds derived from crossing the isogenic and inbred lines were used to study factors that influence the expression of scoliosis. Using the line of birds derived from the cross, the incidence of the lesion, defined as a spinal curve greater than 20 degrees, was influenced by deficiencies of copper, manganese or vitamin B-6. In the cross, scoliosis was expressed in 40-50% of birds. Vitamin B-6, manganese or copper deficiency, however, caused an increase in expression to 60-75% of birds. In contrast, protein deficiency, mild vitamin A deprivation, pantothenic deficiency, food restriction or calcium deficiency did not influence expression. Also, the addition of zinc (400 micrograms/g) or cadmium (5 micrograms/g) to a commercial nonpurified diet did not influence expression. That vitamin B-6, manganese and copper are dietary factors important to the expression of scoliosis may be related to their roles in the formation of connective tissue components, such as matrix glycoproteins, collagen or proteoglycans. For example, alterations and abnormalities in connective tissue may partly underlie progression of scoliosis and its potential for expression.