HYPOPHOSPHATEMIC RICKETS IN RHEAS (RHEA-AMERICANA)

Rickets was diagnosed in 11 rheas from four flocks in Ohio. At necrops y, birds had pliable bones with prominent valgus or varus deformation of the femoral bone and/or the tibiotarsal bone, marked thickening of the metaphyseal plates, and frequent fractures. Histopathologically, b ones of rachitic birds showed marked retention of cartilage core withi n the growth plate, mainly because of a significant lengthening of the hypertrophied zone of the growth plate in relationship to the remaini ng zones. Feed analysis showed that rachitic birds were fed diets havi ng higher calcium/phosphorus (Ca/P) ratios (1.38-4.32) than that of th e diet fed to nonrachitic birds from a different flock (0.65 Ca/P rati o). Serum analysis of blood from clinically rachitic birds from the af fected flocks revealed a marked hypophosphatemia (3.0-4.7 mg/dl), mild hypocalcemia, and normal 25-(OH)-vitamin D concentrations as compared with values in nonrachitic birds, which had serum phosphorus concentr ations of 8.5-8.7 mg/dl. These findings suggest that rickets in growin g rheas was associated with marked hypophosphatemia and improper Ca/P ratios.