Evaluation of vitamin D status of llamas and alpacas with hypophosphatemic rickets

Objective-To evaluate vitamin D concentrations in juvenile llamas and alpacas with hypophosphatemic rickets. Design-Prospective cohort study. Animals-21 llamas (14 with rickets, 7 clinically normal) and 9 alpacas (6 with rickets, 3 clinically normal). Procedures-Blood samples were collected at the time of diagnosis and prior to the initiation of treatment. Serum concentrations of calcium, inorganic phosphorus, and 25-hydroxycholecalciferol (vitamin D₃) were determined on all samples. Comparisons were completed for disease status, age, sex, species, month of birth, and all interactions. Results-Serum concentrations of phosphorus and vitamin D were lower in affected llamas and alpacas than in clinically normal llamas and alpacas, even when mean concentrations were adjusted for age differences. Species (llama or alpaca), sex, and age did not affect any of the metabolite concentrations within this study population. Month of birth influenced vitamin D concentrations and number of affected llamas and alpacas per month. The greatest number of affected llamas and alpacas was identified between January through March, suggesting a seasonal pattern to this syndrome. Treatment of affected llamas and alpacas with vitamin D resulted in increased concentrations of phosphorus and vitamin D. Serum phosphorus concentration was best predicted by 2 independent variables (serum vitamin D concentration and month of birth). Clinical Implications-We believe vitamin D deficiency is the primary cause of hypophosphatemic-rickets of growing camelids, and the observed hypophosphatemia is secondary to a primary deficiency of vitamin D. Appropriate treatment with vitamin D supplements can correct hypophosphatemia and vitamin D deficiency in camelids.