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Introduction Discoveries over the past several decades have revealed that most cells of animal tissues express vitamin D receptors. 1 Many cells additionally have enzymes that convert 25(OH)D, the most abundant circulating metabolite of

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in American Journal of Veterinary Research

because estrogen is thought to play a role in ligament injury in other species. 5 In addition, low vitamin D concentrations have been found in juvenile camelids with developmental orthopedic disease, including angular limb deformities and physeal

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in American Journal of Veterinary Research

Vitamin D–binding protein is part of the extracellular actin scavenging system that facilitates clearance of actin from the circulation. 1 Actin is an intracellular structural protein that is released into the circulation after cell injury and

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in American Journal of Veterinary Research

derived from animals. 2 Supplemental VitD can also be added to diets in the form of a vitamin premix, in addition to any VitD present in raw ingredients. 2 Vitamin D has a crucial role in the maintenance of calcium and homeostasis, 2 and there is

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate temporal changes in bone mineral density associated with seasonal variation in serum vitamin D, calcium, and phosphorus concentrations in alpacas.

Animals—5 healthy mature neutered male alpacas.

Procedure—Metacarpal bone mineral density was measured at 4 times during a year. Each time alpacas were weighed, blood was collected for determination of serum calcium, phosphorus, and vitamin D concentrations, and samples of feed were analyzed for nutrient content. Vitamin D status was determined by use of an assay that measured serum 25-hydroxycalciferol concentration. Effects of changes in serum vitamin D, calcium, and phosphorus concentration and body weight with season on bone mineral density were determined.

Results—Bone mineral density, body weight, and serum vitamin D and phosphorus concentrations varied with season. Bone mineral density, serum vitamin D concentration, and body weight also varied among individual alpacas. Serum vitamin D concentration was lower in January than the previous October and increased from May to the following September. The decrease in bone mineral density lagged behind the decrease in serum vitamin D concentration and was lower in May, compared with the previous October. Body weight was lower in May than the previous October or following September. Solar radiation was highest in July and lowest in December.

Conclusions and Clinical Relevance—Seasonal changes in bone mineral density are associated with changes in serum vitamin D concentrations in alpacas. Changes in bone mineral density associated with a decline in serum vitamin D concentration may predispose some alpacas to developing fractures minimal trauma. (Am J Vet Res 2002; 63:948–953)

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in American Journal of Veterinary Research

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 Dy 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 (Ilama 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 secopdary to a primary deficiency of vitamin D. Appropriate treatment with vitamin D supplements can correct hypophosphatemia and vitamin D deficiency in camelids. (J Am Vet Med Assoc 1996; 209:1128-1133)

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in Journal of the American Veterinary Medical Association

In the Timely Topics in Nutrition report “Vitamin D metabolism in canine and feline medicine” (J Am Vet Med Assoc 2017;250;1259–1269), Figure 1 is incorrect. There should not be an arrow between 1,25-(OH) 2 -D (calcitriol) and 24,25-(OH) 2 -D

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in Journal of the American Veterinary Medical Association

Vitamin D Metabolism and Hormonal Influences In many species, the biosynthesis of vitamin D begins with exposure to UV light, wherein 7-dehydrocholesterol is transformed to previtamin D 3 . Factors that affect synthesis of vitamin D 3 include

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the interaction of season and age on serum calcium, phosphorus, and vitamin D3 concentrations in llamas and alpacas.

Animals—23 clinically normal llamas and 7 alpacas.

Procedures—Animals were assigned to 1 of the 3 following groups on the basis of age at the start of the study: adult (age, ≥ 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 ≥ 2.0.

Conclusions and Clinical Relevance—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. (Am J Vet Res 2001;62:1187–1193)

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in American Journal of Veterinary Research

increases serum concentrations of both calcium and 1,25(OH) 2 D 3 , which also has a crucial role in calcium homeostasis. 15,16 Oral and parenteral administrations of vitamin D 3 (cholecalciferol) and its metabolites (eg, 1,25[OH] 2 D 3 ) to dairy cows

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in American Journal of Veterinary Research