Field Rickets in Turkeys: Relationship to Vitamin D

Thirty-two outbreaks of leg disorders in turkeys were investigated during 1981-1985. Among them, 22 were characterized by a low percentage of bone ash and were considered as field rickets. Most of the field rickets cases exhibited reduced plasma calcium and inorganic phosphorus. Plasma 25-hydroxyvitamin D3 and intestinal calcium-binding protein were lower in the rachitic than in normal turkeys. These symptoms are typical of rickets resulting from vitamin D deficiency. The vitamin D3 equivalence of a diet that had been fed during field rickets outbreaks was assayed biologically and found to be 111 micrograms/kg diet, about eight times the minimal requirement. In two other cases no symptoms of rickets were observed in turkeys fed diets that had been previously consumed during field rickets outbreaks. The results indicate that in some cases of field rickets there was no involvement of dietary factors and confirm a previous suggestion that field rickets may result from defects in metabolism of vitamin D3, or in its expression.