Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter | 22 Trace Minerals
the patterns are similar suggests common chemical principles
have persisted as a part of natural selection. To the
extent that the ionic potential of an element is related to
its relative abundance in seawater, one can argue that evolutionary
choice as it relates to metal utilization is based in
part on chemical properties that dictate its interaction with
water. For example, when the ionic potential is high ( 10),
the positive ion appropriates one or more oxygen ions, freeing
the hydrogen and forming an oxyanion. Oxyanions are
generally soluble; thus, relative to the earth’s crust, the log
enrichment is high. This is a characteristic of the nonmetals
in the upper right corner of the periodic table (e.g., C, N, O,
S, P). Such elements are also the smallest in size to form stable
multiple bonds. With time carbon can become a carbonate
ion in water and eventually CO 2 (O C O, a gas) when
oxidized further. Contrast that with silicon, carbon’s tetravalent
homologue in period 4 of the periodic table. Silicon in
water forms silicates, which easily polymerize and are oxidized
to the end product silicon dioxide or quartz, a solid,
because of the inability to form stable multiple bonds:
| | | | |
-Si-O-Si-O-Si-O-Si-O-Si-
| | | | |
O O O O O
| | | | |
-Si-O-Si-O-Si-O-Si-O-Si-
| | | | |
For elements with low to intermediate ionic potential
values, such as silicon (IP log 0.5), the log of the enrichment
factor is often in the range of 1 to 1, indicating
small enrichment or even depletion relative to the crust.
Metals with low, but positive, intermediate, or slightly
negative ionic potentials tend to form hydroxides in water,
most with low solubility. Many of the essential trace elements
fall in this category. Finally, elements with negative
ionic potentials tend to form hydrated shells and interact by
organizing water structure, a role that is important to understanding
the functions of Na, K, Mg, and Ca in cells.
2 . Utilization of Trace Elements and Metabolic Regulation
and Metabolism
As an additional perspective, it can be generalized that dietary
requirements across species ( Table 22-2 and Fig. 22-2 )
are more similar than dissimilar ( Rucker, 2007 ). This is particularly
the case when given requirements are expressed
per unit of energy consumed or per unit weight of ration.
Figure 22-2 shows the relationship for selected mineral
requirements and metabolic body size. The requirements of
trace elements scale allometrically in a manner that is similar
in principle to scaling algorithms (e.g., kWt 3/4 ) for basal
metabolism. If a set of common principles was involved in
Log
Approx.
Daily
Need
In
Mg
2
1
0
Approx.
1
Daily 25
Need
X
In
Mg
0
0 25 50 75 100
X
Body weight in Kg
2
2 1 0 1 2 3
Log body weight in Kg
FIGURE 22-2 Relationship of mineral requirements and metabolic
body size. Log plots of the daily intake of selected minerals for mice, rats,
chickens, dogs, humans, and pigs versus their respective body weights in
kilograms. The data for individual minerals plotted in this fashion result
in reasonably linear plots with slopes that range from 0.6 to 0.8. For any
given mineral, plots of daily intake versus units of body weight are not
linear and require polynomial equations to describe the function (insert).
the selection of the elements important to life, it follows
that nutrition requirements would be influenced by the same
principles (e.g., all cells utilize in principle the same metabolic
strategies). Indeed, a strong case can be made that
when expressed per unit of food-derived energy or relative
to metabolic body size, requirements for essential elements
are similar for a diverse array of species. As substances
important to catalyst and entasis, it follows consequently
that their relative nutritional needs are also driven by factors
and principles important to energy utilization.
Why do deficiencies or excess occur Nutritional deficiencies
obviously result when the intake of essential nutrients
consistently falls below the minimal requirement (i.e.,
a primary deficiency). In animal nutrition this is regrettably
common given the tendency to feed monotonous diets
or foods common to a given region. Secondary mineral
deficiencies can also arise through a variety of mechanisms
that include poor bioavailability, interactions with
other competing substances, and genetic influences (e.g.,
polymorphisms that dictate an increased need for given
nutrients; Keen, 1996 ). Table 22-3 provides a list of several
mechanisms underlying the development of deficiencies
and common interactions that will be amplified in each of
the sections that follow.
II . COBALT
A large animal (50 to 100 kg) can contain 1 to 2 mg of Co
with liver containing about 0.1 mg (1.7 μmol), skeletal muscle
0.2 mg (3.4 μmol), bone and hair 0.3 mg (5.1 μmol) each,
and adipose tissue 0.4 mg (6.8 μ mol) ( Smith et al. , 1987 ).
X
50
X
Mn
Zn
Zinc
Cu
X