WildLife Group
of the SAVA
Hypomagnesemia,
Hypocalcemia, and
Ruminants in Captive
RUMINANTS – AN UNDER RECOGNIZED SYNDROME?
Michele Miller DVM, MPH, PhD, DECZM (ZHM)*,
Martha Weber DVM, DACZM, Eduardo Valdes PhD,
Deidre Fontenot DVM, Donald Neiffer VMD, DACZM,
P.K. Robbins MRCVS, Scott Terrell DVM, DACVP, and
Mark Stetter DVM, DACZM
Abstract
Macro- and microminerals play a critical role
in maintaining normal physiologic processes.
Requirements for domestic ungulates have been
extensively studied and are available through
the National Research Council (NRC).4 These
values are used when creating balanced diets for
production animals. However, normal values have
not been established for most wildlife species.
Due to specialized feeding habits, extrapolation
from domestic cattle may not be applicable to
grazing and browsing wild ruminants. Therefore,
collection of baseline data for each species is needed
to develop nutritionally sound diets for captive
wildlife and provide comparative information for
detection of nutritional diseases.3 Several cases of
hypomagnesemia in captive ungulates are described
in this report.
Mineral Metabolism Overview
Calcium – The majority of the body’s calcium is
stored in the skeletal system. It plays a major
role in muscle function, nerve conduction, and
enzymatic processes.5 In general, the levels of
calcium in roughages are highest in legumes (alfalfa/
14
lucerne), then grasses and hays, and lowest in grains.
Absorption of calcium from the diet is affected by
multiple factors, including the presence of oxalates,
adequate levels of calcium and phosphorus (at a
1:1 to 2:1 ratio), and relative balance of parathyroid
hormone, calcitonin, and vitamin D. Hypocalcemia
seen in late pregnancy and lactation is due to an
imbalance in homeostasis, rather than a dietary
deficiency.5 Acute signs include: stiffness, followed
by tetany, weakness, decreased rumen motility,
shock and death. Inadequate dietary magnesium
increases the risk of hypocalcemia. Chronic signs
include: reduced feed intake, poor growth, rickets,
osteomalacia, lameness and hunched stance, and
pathologic fractures.
Phosphorus – This mineral is important in skeletal
structure and as a source of chemical energy
(ATP). Serum levels are not as closely regulated as
those of calcium and vary with dietary intake and
renal excretion. Levels in feedstuff are high in oil
seeds, moderate in grains, and lowest in grasses
and legumes.5 High phosphorus diets tend to
suppress calcium absorption and predispose to the
development of uroliths.