Diet design By Patrick Charlton
T r
a c
e
m i ne
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als
:
imeforchang e?
Organic trace minerals meet growing animal nutritional needs while
helping to address environmental concerns stemming from overfeeding
of their inorganic counterparts.
From the 1950s to the 1990s, most trace mineral supplementation
of animal diets was in the form of inorganic minerals and these
largely eradicated associated deficiency diseases in farm animals.
However, since the 1960s, food animal production has intensified and
genetic potential for growth and yield has improved.
This increase in demand on all aspects of nutrition has led to
the use of new ingredients better able to meet the animal’s growing
needs. In the case of trace minerals, this has come in the form of
organic minerals. ‘Organic minerals’ is a loose term—describing
mineral sources bound in some way to an organic ligand. Chelated
trace mineral technology allowed commercial application of these
products to improve trace mineral status in the dairy herd with wide
ranging benefits. Probably the best definition of chelates today is the
AAFCO definition which splits chelates into five different groups:
■ Metal Amino Acid Complex
■ Metal (specific amino acid) Complex
■ Metal Amino Acid Chelate
■ Metal Polysaccharide Complex
■ Metal Proteinate
The above descriptions are defined by the ligand binding and
source, with soy-based peptide and amino acid bound trace minerals being the most commercially popular sources used in feed. This
chelation technology is only possible with the transition metals (iron,
copper, manganese, cobalt and zinc). The chemical state of the other
t wo key trace minerals in dairy nutrition—iodine and selenium—make it
impossible to produce a ‘chelated’ version of these trace minerals.
Selenium differs
However, organic selenium sources have been available in the
global feed industry since the early 1990s with the introduction of
a selenium yeast product. The technology used in the production
of this trace mineral source is different from the other organic
minerals for the reasons stated above. Scientists took a lead from
‘Mother Nature’ in understanding how plants accumulate selenium
in their tissues. Selenium is taken up and stored in plant tissue
by replacing sulfur in the sulphur-containing amino acids such as
methionine or cystine.
Figure 1: Effect of various copper sources on copper in
livers of heifers
100
Oxide
+171%
80
79.3
Liver, Copper, ppm
60
40
Sulphate
Biplex®
+139%
56.8
+38%
34. 3
29. 3
24.8 23. 7
20
0
Initial 28 Days
The above figure shows the effect of copper sources on copper in livers
of heifers fed added sulphur (. 15 percent) and molybdenum ( 5 ppm).
Source: Hemken, University of Kentucky.
Likewise, selenium-enriched yeast is produced by making selenium available in a sulfur deficient media used in the yeast propagation.
The real technology here revolves around the selection of a yeast strain
that will accumulate high enough levels of this bio-available selenium
source to make supplementation in dairy diets cost effective.
The product landscape for organic selenium sources is much
easier for the buyer than with chelates, with only a few selenium-yeast
products available for use, and only one of these having gone through
both FDA (USA) and European Union (EU) approval processes.
Optimum versus adequate
Dairy nutritionists aware of the low availability of inorganic forms
commonly use high quantities of trace minerals in an effort to guarantee uptake of the required quantity by the animal. However, in
