title: Seasonal changes in serum calcium, phosphorus, and vitamin D concentrations in llamas and alpacas.
abstract: OBJECTIVE
  To evaluate the interaction of season and age on serum calcium, phosphorus, and vitamin D3 concentrations in llamas and alpacas.
  
  
  METHODS
  23 clinically normal llamas and 7 alpacas.
  
  
  METHODS
  Animals were assigned to 1 of the 3 following groups on the basis of age at the start of the study: adult (age, > or = 24 months; n = 8), yearling (> 12 but < 20 months; 5), and neonate (< 6 months; 17). Twelve serum samples were obtained at monthly intervals. Calcium, phosphorus, and vitamin D3 concentrations were measured, and the calcium-to-phosphorus concentration (Ca:P) ratio calculated. Effect of season and age on each of these variables was determined.
  
  
  RESULTS
  Vitamin D3 concentrations varied significantly as a function of season; the highest and lowest concentrations were detected September through October and February through March, respectively. The seasonal decrease in vitamin D3 concentration was significantly greater in neonates and yearlings, compared with adults. Serum phosphorus concentration decreased as a function of age, with the most significant seasonal change detected in the neonate group. The Ca:P ratio in neonates varied between 1.1 and 1.3 except during winter months when it increased to > or = 2.0.
  
  
  CONCLUSIONS
  Mean vitamin D3 concentration varied by > 6 fold in neonatal and yearling llamas and alpacas and > 3 fold in adult animals as a function of season. These results support the hypothesis that seasonal alterations in vitamin D3 concentrations are a key factor in the development of hypophosphatemic rickets in llamas and alpacas.
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis 97331-4802, USA.
authors.forename: B B
authors.initials: BB
authors.lastname: Smith
authors.forename: R J
authors.initials: RJ
authors.lastname: Van Saun
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000097:blood*; D002161:Camelids, New World / Q000097:blood*; D002762:Cholecalciferol / Q000097:blood*; D005260:Female; D008297:Male; D010758:Phosphorus / Q000097:blood*; D012621:Seasons; D012737:Sex Factors
chemical_list: D002762:Cholecalciferol; D010758:Phosphorus; D002118:Calcium