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)
Objectives—To determine whether feed restriction
induces hepatic lipidosis (HL) in llamas and to evaluate
the metabolic changes that develop during feed
Animals—8 healthy adult female llamas.
Procedure—Llamas were fed grass hay at a rate of
0.25% of their body weight per day for 13 to 28 days.
Llamas were monitored by use of clinical observation,
serum biochemical analyses, and ultrasound-guided
Results—All 8 llamas lost weight and mobilized fat.
Five llamas developed HL, including 4 that were nursing
crias. During the period of feed restriction, mean
serum concentration of bile acids and activities of
aspartate aminotransferase (AST), sorbitol dehydrogenase
(SDH), and γ-glutamyl transferase (GGT) were
significantly higher in llamas that developed HL, compared
with llamas that did not. Mean insulin-to-cortisol
concentration ratios were lower in llamas with HL
before and up to 7 days of feed restriction, compared
with those that did not develop HL.
Conclusions and Clinical Relevance—HL in llamas
may be induced by severe feed restriction, particularly
in the face of increased energy demand. Llamas
with weight loss attributable to inadequate dietary
intake may develop biochemical evidence of
hepatopathy and HL. Increases in serum concentration
of bile acids and activities of GGT, AST, and SDH
may indicate the development of HL in llamas and
identify affected animals for aggressive therapeutic
intervention. (Am J Vet Res 2001;62:1081–1087)
Objective—To determine blood glucose clearance in
2 species of New World camelids after IV challenge
and to examine mechanisms of this clearance.
Animals—5 adult female llamas and 5 adult gelded
Procedure—After food was withheld for 12 hours,
camelids received 0.5 g of glucose/kg of body weight
by rapid IV infusion. Serum concentrations of glucose,
nonesterified fatty acids, cortisol, and insulin, and
plasma concentrations of lactate were determined
before and 0, 1, 2, 3, 4, 5, 15, 30, 60, 90, 120, 180,
and 240 minutes after infusion. Ratios of insulin to
glucose and insulin to cortisol were calculated for
each time point.
Results—Postinfusion glucose concentrations were
significantly higher in llamas than alpacas for the first
15 minutes and remained significantly higher than
baseline values in both species for 180 minutes.
Lactate and cortisol concentrations did not change
significantly; nonesterified fatty acid concentrations
decreased in both species 30 minutes after infusion.
Baseline insulin concentrations were < 6 μU/ml in
both species and increased only to 10.1 ± 0.7 μU/ml
in llamas. Insulin concentrations did not change significantly
Conclusions and Clinical Relevance—Llamas and
alpacas clear glucose more slowly than other domestic
species after challenge, mainly because of a weak
insulin response and slow cellular uptake. This
response may impair the assimilation of exogenous
glucose as well as make llamas and alpacas prone to
diabetes-like disorders when an abundance of
endogenous or exogenous glucogenic agents are present.
(Am J Vet Res2001;62:682–686)
Objective—To evaluate temporal changes in bone
mineral density associated with seasonal variation in
serum vitamin D, calcium, and phosphorus concentrations
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
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
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;