Seasonal interaction of serum vitamin D concentration and bone density in alpacas.
OBJECTIVE
To evaluate temporal changes in bone mineral density associated with seasonal variation in serum vitamin D, calcium, and phosphorus concentrations in alpacas.


METHODS
5 healthy mature neutered male alpacas.


METHODS
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
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.
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis 97331-4802, USA.
Jill E
JE
Parker
Karen I
KI
Timm
Bradford B
BB
Smith
Robert J
RJ
Van Saun
Kerri M
KM
Winters
Peerapol
P
Sukon
Christine M
CM
Snow
D000818:Animals; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D002118:Calcium / Q000097:blood; D002161:Camelids, New World / Q000097:blood*; D008297:Male; D010758:Phosphorus / Q000097:blood; D012621:Seasons; D014807:Vitamin D / Q000097:blood*
D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium