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BESTUUR / MANAGEMENT
Perspective on
mineral supplements
By Dr Jasper Coetzee, sheep nutrition and management specialist consultant
Livestock breeders have to familiarise
themselves thoroughly
with mineral shortages and/or
imbalances that may occur, as
these can have a negative effect
on the production, reproduction and
health of grazing animals and the digestion
of their feed. The cost of rectifying
these problems is often negligent compared
to the results achieved.
Production and reproduction tempo, as
well as the health of grazing sheep and
cattle, are often adversely affected by the
occurrence of marginal mineral shortages
and/or imbalances, which have a significant
impact on animal performance even
before any clinical (visible) signs of shortages
are observed.
Production losses
It is estimated that mineral and vitamin
shortages can bring about a 2% loss in
overall production in sheep (Court et al.,
2010). One factor that is often ignored, is
that the micro-organisms in the rumen of
the ruminant require a series of minerals
to ensure optimal and effective digestion
of ingested grazing. These shortages can
be the direct result of too low levels of
minerals in the grazing, or of excessive intake
of certain minerals known as antagonists.
Animals’ mineral requirements are
highly dependent on their physiological
stage and productivity level, which means
that, as the animal’s production and reproduction
increase due to crossbreeding, selection
progress and/or improved management
practices, its mineral requirements
will increase accordingly. Marginal mineral
shortages in animals presenting a low production
level, will increase even more as
production and reproduction increase.
The mineral and vitamin requirements
of ruminants have been published in various
text books and articles. These tables
reflect the estimated minimum requirements
(Lee et al., 2002) of an average animal
under normal conditions, but do not
take into account the differences between
animals, grazing and the environment. In
other words, these tables serve only as a
guideline.
Feed scientists do estimates based on
grazing, soil and water analyses, as well as
tissue, blood and bone analyses of animals,
to determine which minerals and at which
levels should be supplemented via licks
for animals on a specific farm, especially
where animals are not performing according
to their genetic potential.
Monitoring
Continued monitoring of the mineral status
of a sheep and cattle herd, as well as
the observation of typical symptoms of
mineral shortages, is an essential part of
a general management programme. Socalled
dose response trials are often used
as opposed to a control, in order to confirm
a shortage and to determine a reaction to
a supplement.
When determining livestock’s mineral
requirements, one should always consider
the possibility of extreme climate conditions
and the fact that animals’ needs increase
as they move over great distances
while searching for grazing. However, animals’
mineral requirements become less
important when they are exhibiting an energy
and/or protein shortage.
It therefore appears to be uneconomical
to supply mineral supplements to grazing
animals if they are experiencing an energy
and/or protein shortage. On the other
hand, if energy and protein are sufficient, a
high level of minerals is required to maintain
a high growth rate. Mineral shortages
and/or imbalances can be rectified by supplementing
it in licks specially formulated
to supplement shortages in a natural manner.
It is also the most economical method
to supplement mineral shortages.
Beware of too much
Grazing animals obtain their minerals by
ingesting grazing, water, soil and licks.
Often too high levels of certain minerals,
so-called antagonists (such as calcium,
iron, sulphur, molybdenum, sodium and
potassium), occur in one or more of these
sources. This has a negative effect on the
absorption of other minerals and leads to
mineral shortages.
For example, a too high intake of calcium
from lime-rich drinking water can
lead to a shortage of manganese, zinc, selenium,
copper, cobalt, iodine, phosphorus,
magnesium and vitamin A. It is therefore
recommended that part (30 to 50%) of
the trace elements in a lick is supplied in
organic format (Short, 2006).
Supplementation of minerals, trace
elements and vitamins for grazing animals
cannot be done only through licks – not
all animals eat licks or take in sufficient
amounts of lick. Up to 18% of the sheep
in a herd don’t ingest any lick (Lobato
et al., 1980) and up to 30% don’t ingest
sufficient amounts of lick (Pinchak, 2000).
Approximately 17 to 38% of cattle in three
studies ingested no lick, while up to 30%
ingested only small amounts of the lick
(Bowman & Sowell, 1997).
This lends credibility to the view that,
during strategic times of the year (prior
to the breeding seasons, before the lambing
and calving season, at weaning and
upon introduction to a feedlot), an additional
trace mineral supplement must be
given via a dosage or injection of trace
elements.
Macro-minerals can only be supplemented
via licks and producers should
aim for their animals to ingest the recommended
amount of lick. Include the correct
level in intake-inhibitors in the licks
and practise correct lick trough management
(e.g. placement of lick troughs).
For more information, phone the author
on 076 846 8800 or email
jasperco@iafrica.co.za. SB
Issue 35 ▪ July 2013
39