Post Mortal Mineral Analysis
in African Wildlife
Dr Rick Last – BVSc; M.Med.Vet(Path)
Specialist Veterinary Pathologist
Introduction
Trace mineral and deficiencies / imbalances are
significant contributors to fetal, neonatal and post-
natal losses, as well as having important impacts on
growth, habitat adaption, species survival, production
and reproductive performance in African wildlife.
Such micronutrient imbalances or emerging as
significant disease entities as intensification in the
industry gains momentum. Therefore, evaluation
of micronutrient levels is becoming an important
component of the routine disease investigation post-
mortem in African wildlife.
The primary means of mineral analysis in the post-
mortem setting is on liver tissue and / or bone.
Minerals analyzed on liver tissue include selenium,
copper, iron, zinc and manganese. Bone on the other
hand is used for analyzing calcium, phosphorus,
magnesium and fluoride.
Liver analysis
Hepatic mineral analysis is currently primarily
used in wildlife to determine whether a nutrient
deficiency or toxicity possibly exists. With the collation
of mineral levels for various species over time
recommended guideline levels will start to emerge
and then evaluation of endogenous reserves for a
specific mineral will be possible. The beauty of this
procedure is that it can be performed on formalin
fixed liver tissue which has major practical benefits
to the wildlife veterinarian performing autopsies
in the field. Variou s scientific studies evaluating
the effect of preserving liver tissue in formalin on
the concentration of trace mineral levels, found no
statistically significant difference in the concentrations
in formalin fixed liver (stored for up to a month),
compared to fresh or frozen liver.
Recommendations for the sampling of liver tissue for
mineral analysis include the following:
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A minimum of 20 g of liver tissue is required
(equivalent to a tissue block of 3 cm x 3 cm
dimensions).
Only 10% buffered formalin should be used for
preservation, as mineral dilution can be expected
with non-buffered formalin solution.
Liver tissue block should be fixed in the 10%
buffered formalin for a minimum of 24 hours
before the analysis is performed.
Submit the sample as per the normal routine
procedures for histopathological specimens to
the veterinary diagnostic laboratory.
Normal micronutrient levels are significantly affected
by age, with normal foetus and neonatal levels
being significantly higher than post-natal and adults,
and so the age of the animal needs to be taken
into consideration when analysing levels. The dam
preferentially pushes trace minerals into her foetus, so
if the neonate has a low trace mineral status, it is due
to the mother`s low status. This holds true for Zn, Fe,
Cu and Se.
It is important to remember that these trace
minerals are toxic in excessive amounts and so
over supplementation can result in toxicity. The
risk of toxicity is obviously far greater where
injectable multimineral preparations are used
for supplementation in place of balancing of the
nutrition provided. There is also growing concerns
regarding the sensitivity of certain antelope species
2017
October
9