Trace elements for animals

Proven essential elements

Subsequently, elements with proven essentiality are discussed.

Boron

Only in the last 15 years has it become clear that boron is also essential for human and animal nutrition. Animal organisms, though their requirement is considerably lower compared to plants, show symptoms that are almost as obvious when the supply is deficient.

Chloride

Together with sodium, chloride is one of the most important ions as regards quantity in the extra-cellular spaces. They have an effect both on the total volume and on osmotic pressure.
In addition, there are numerous functions at cellular level. The transport of most of the other ions as a rule requires chloride or sodium dependent cotransporters or antiporters.

Chloride and sodium deficiency show up in identical symptoms. The resultant hypoosmolarity leads to the movement of water into the tissues (in particular the brain) and can in extreme cases be fatal.

Fluoride

Whether fluoride is one of the essential trace elements is still under discussion today. It has been observed in various studies that fluoride deficiency during pregnancy and in the first year of life delays growth, which indicates unknown cellular mechanisms. Its importance for the hardness and chemical resistance of bones and teeth is, on the other hand, undisputed.

The resorption of fluoride varies greatly, depending on its combination with nutritional elements. In a watery solution it is absorbed almost quantitatively, with approx. 25 % already being resorbed in the stomach.

Due to its limited presence in our soils, fluoride is only present in our foodstuffs in a very low concentration. However, some plants do enrich certain elements well over their own requirements; black tea, for example, has a good available content of organically bound fluoride (~ 1 mg/l F^- in the form of easily resorbed fluoroacetic acid).

Iodine

Germany, Switzerland and Austria are classic areas of iodine deficiency. In tropical and subtropical areas, the situation is often much better in this respect, although few actual values are given in aquarium literature. However, I can give one value. According to Kaspar Horst, the iodine content in the inland waters of Sri Lanka is between 140 ppb and 320 ppb. This is several times the amount that can be supplied by our tap water or even reverse osmosis water.

In contrast to animals, plants to not require iodine. However, they absorb it relatively non-specifically, as they do many other mineral substances, so that it is available to herbivores in this form.

Iodine is an essential component of the thyroid hormones, without which higher animal life cannot function. Thyroid hormones regulate the basic metabolism and the use of energy. The exact metabolic process is as yet largely unclear.

Copper

The copper-plasma level is fairly constant and largely uninfluenced by nutrition. In the blood, copper is mostly bound to transcuprein and albumin. After entering the liver the copper is largely stored in the target proteins or returned to the blood as copper ceruloplasmin (= copper transport form). Secretion via the gallbladder represents the most important regulation value for copper homeostasis.

Copper is an important component in the endogenous, antioxidative system. Part of this is the copper-zinc superoxide dismutase (CuSOD) and the cytochrome C oxidase (CCO), which is involved in the transport of electrons in the mitochondria.

The functions of copper are however not limited to the antioxidative system or the transport of electrons. Copper ceruloplasmin is also involved in oxidation of Fe²⁺ to Fe³⁺. Only in this way can stored iron be bound to transferrin, which explains the close connection between copper and iron status.

Further enzymes containing copper are lysosyloxidase (plays a central part in the connections of elastin and collagen) and dopamine-β-hydroxylase (catalyses the reaction of dopamine to noradrenalin ascorbate as an electron donor. Some influences on the immune system that cannot be exactly verified take place via interleucin-2).

Decapods (crabs, prawns and shrimps) have developed a copper-porphyrin complex instead of an iron-porphyrin complex (haem). Despite greater individual sensitivity to this metal ion, they nonetheless require copper as a trace element for this purpose also.

Sodium

see Chloride

Selenium

is one the one hand a semi-metal with semi-conductor qualities, and on the other behaves in many reactions in a manner very similar to sulphur, and can replace the latter in many compounds. Amino acids containing selenium are also of biological importance, as are other compounds derived from the corresponding compounds containing sulphur.

Over 20 such proteins or protein components containing selenium are known to date. They fulfil important protective oxidative functions in the body's own redox systems:
glutathione peroxidase, thioredoxin reductase, production of the thyroid hormone T4, DNA-repair mechanisms, apoptosis in tumour cells.

Vanadium

Vanadium has been proved to be essential only in human beings. Vanadium deficit, in various different biological systems, results in growth disruption, as well as in sodium retention oedema due to the lessening of the efficiency of the renal Na-pump. In the fat cells of rats, vanadium influences glucose oxidation to the same extent as insulin. Vanadium improves the ability of the erythrocytes to transport oxygen, as well as the potassium permeability of cell membranes. It also influences the activity of enzymes, such as adenyl cyclase, alkaline phosphatase, NADH-oxydase, phosphofructokinase and ribonuclease.

Non-proven essential elements

Subsequently, elements with undetected essentiality are discussed.

Lithium

The importance of lithium as a trace element has not been finally clarified, but it seems to have positive effects on brain metabolism.
In animal experiments, lithium deprivation has caused low birth rates, higher rates of miscarriage, changes to enzyme activity and behaviour disruption. In human beings, the symptoms of deficiency have not been described, which is why the essential status of lithium is disputed. Epidemiological studies however lead us to assume that in areas of higher lithium absorption the incidence of suicide is lower.

Nickel

Ni(II) has similarities to Fe(II). Little is known about the metabolism. Resorption in the small intestine is at about 1 - 10 %; synergism with iron is assumed here. Nickel deficit in animal experiments has led to disruption of the utilisation of iron and also the formation of blood. To date, however, it has not been possible to prove that nickel is a component part of the human enzyme system.

Nickel is better known because of its toxicity in higher doses. Allergies to nickel are also common, usually showing up as contact eczema in the case of cheap jewellery and metalware.

Silicon

It is assumed that silicon has a function in the formation of bones and in the metabolism of connective tissue.
However, there is no proof of its essential status, and no symptoms of deficiency are known.

Tin

As tin is found at oxidation levels Sn²⁺ and Sn⁴⁺, involvement in the body's own redox systems and importance for the tertiary structure of proteins is theoretically possible. It is better absorbed as an organic complex; inorganic tin is barely useable.
Tin has been counted among the essential elements since its stimulating effects on growth in rats were discovered. Some involvement in gastrin, which regulates the production of hydrochloric acid in the stomach, is being discussed. To date, however, there is no proof of the essential nature of its effects on human beings.
The toxic effects of higher doses (mainly intestinal effects) are however well known and documented.