The resultant products are highly soluble and generally disassociate in solution. These result on combining soluble metals and soluble organic acids such as propionic acid. Similarly, the utilization of Fe from Fe-citrate, Fe-fumarate and Fe-gluconate is essentially equal to that of ferrous sulphate (Ammerman et al., 1995). The utilization of Co by sheep fed dietary levels of 40 to 60 mg/kg was equal from cobalt-sulphate and cobalt-glucoheptonate (Henry et al., 1997 Kawashim et al., 1997). (1998) did not find improved Zn bioavailability using either Zn-gluconate or Zn-acetate. (2005) found similar growth performance in pigs on using reduced level (500 mg/kg) of Zn-polysaccharide complex (Zn-PS) as compared with pharmacological level (300 mg/kg) of ZnO. Many studies have reported no beneficial effect on animal performance. These are larger molecules based on chains of simple sugars that are known to be highly soluble in the digestive tract. These are generally prepared by coating the metal with polysaccharide molecules. Though the metal proteinates are less expensive, they are not much beneficial when compared with single amino acid chelates. Such molecules are easily broken apart especially with change in pH, resulting in the loss of heterocyclic chelate ring structure. Moreover, this product has a structure that does not have a very high stability constant because of the size of its ligand. As a result, the molecular size of metal proteinates sometimes is higher than the desired size which decrease bioavailability of minerals. The final product may contain single amino acids, dipeptides, tripeptides or other protein derivatives. These result from chelation of a soluble mineral salt with amino acids and/or hydrolyzed protein. Supplementation of zinc with glycine chelate improves the growth performance of pigs (Wang et al., 2010) and broiler birds (Feng et al., 2010). Nowadays trace mineral glycinate using glycine as a ligand is getting popular as glycine is readily absorbed in gut and gets transported right into the cells. The molecular size of such chelates should not exceed 800 Dalton. These are formed from the reaction of a metal ion from a soluble metal salt with amino acids having a mole ratio of one mole of metal to one to three (preferably two) moles of amino acids to form coordinate-covalent bonds. For instance for a zinc complex in this category, the blend would include zinc methionine, zinc lysine, zinc leucine, zinc cystine, etc. Each individual molecule is still one metal ion and one amino acid but has a variety of amino acids in the blend. Metal amino acid complexes: These are characterized by a metal atom (zinc for instance) complexed with several single amino acids.These complexes are most effective and efficiently absorbed in gut among all the organic minerals. Other such common complexes include copper lysine and manganese methionine. For instance, one of the most common metal complexes is zinc methionine which is produced by combining zinc sulfate and amino acid methionine. ![]() These are the products resulting from complexing a soluble metal salt with a specific amino acid. Metal (specific amino acid) complexes. ![]() Different categories of organic trace mineralsĬategories of organic trace minerals as defined by Association of American Feed Control Officials (AAFCO, 1998) include: Another potential application of the organic mineral sources is reduction in their excretion and thereby reduction in the environmental pollution. Supplementation of organic mineral complexes is reported to improve animal production. Common organically bound trace minerals used in animal nutrition are iron, copper, zinc, manganese, chromium and selenium. When minerals are bound to chelating agents such as amino acids or hydrolysed proteins they become more stable and less reactive in the digestive tract. One of the reasons for increased bioavailability of organic minerals is that they are protected from such interactions. ![]() The inorganic minerals may interact with fibre, phytate, tannin, oxalate, silicates or other minerals in the gastro-intestinal tract, which may interfere with their absorption. Mineral chelates are organic trace minerals designed to enhance gut absorption and improve bioavailability. The other category is often referred to as “chelates”. Inorganic sources are the common sulphates, oxides, chlorides, carbonates of the element and they can differ in their bioavailability. Two broad categories of sources are available to supplement trace elements: inorganic and organic sources. Trace elements have an important role in various metabolic events in the body. Gowda, Division of Animal Nutrition, National Institute of Animal Nutrition and Physiology, Bengaluru, India 560 030 Description
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