Animal feed resources information system

Organic trace minerals for improving livestock production

Broadening Horizons N°17, May 2015

D. T. Pal and N. K. S. Gowda, Division of Animal Nutrition, National Institute of Animal Nutrition and Physiology, Bengaluru, India 560 030


Trace elements have an important role in various metabolic events in the body. Two broad categories of sources are available to supplement trace elements: inorganic and organic sources. Inorganic sources are the common sulphates, oxides, chlorides, carbonates of the element and they can differ in their bioavailability. The other category is often referred to as “chelates”. Mineral chelates are organic trace minerals designed to enhance gut absorption and improve bioavailability. 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. One of the reasons for increased bioavailability of organic minerals is that they are protected from such interactions. 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. Common organically bound trace minerals used in animal nutrition are iron, copper, zinc, manganese, chromium and selenium. Supplementation of organic mineral complexes is reported to improve animal production. Another potential application of the organic mineral sources is reduction in their excretion and thereby reduction in the environmental pollution.

Different categories of organic trace minerals

Categories of organic trace minerals as defined by Association of American Feed Control Officials (AAFCO, 1998) include:

  • Metal (specific amino acid) complexes. These are the products resulting from complexing a soluble metal salt with a specific amino acid. For instance, one of the most common metal complexes is zinc methionine which is produced by combining zinc sulfate and amino acid methionine. Other such common complexes include copper lysine and manganese methionine. These complexes are most effective and efficiently absorbed in gut among all the organic minerals.
  • Metal amino acid complexes: These are characterized by a metal atom (zinc for instance) complexed with several single amino acids. Each individual molecule is still one metal ion and one amino acid but has a variety of amino acids in the blend. For instance for a zinc complex in this category, the blend would include zinc methionine, zinc lysine, zinc leucine, zinc cystine, etc.
  • Metal amino acid chelates. 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. The molecular size of such chelates should not exceed 800 Dalton. 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. Supplementation of zinc with glycine chelate improves the growth performance of pigs (Wang et al., 2010) and broiler birds (Feng et al., 2010).
  • Metal proteinates. These result from chelation of a soluble mineral salt with amino acids and/or hydrolyzed protein. The final product may contain single amino acids, dipeptides, tripeptides or other protein derivatives. As a result, the molecular size of metal proteinates sometimes is higher than the desired size which decrease bioavailability of minerals. Moreover, this product has a structure that does not have a very high stability constant because of the size of its ligand. Such molecules are easily broken apart especially with change in pH, resulting in the loss of heterocyclic chelate ring structure. Though the metal proteinates are less expensive, they are not much beneficial when compared with single amino acid chelates.
  • Metal polysaccharide complexes. These are generally prepared by coating the metal with polysaccharide molecules. These are larger molecules based on chains of simple sugars that are known to be highly soluble in the digestive tract. Many studies have reported no beneficial effect on animal performance. Case and Carlson (2002) and Buff et al. (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. Sandoval et al. (1998) did not find improved Zn bioavailability using either Zn-gluconate or Zn-acetate. 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). 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).
  • Metal propionates. These result on combining soluble metals and soluble organic acids such as propionic acid. The resultant products are highly soluble and generally disassociate in solution.
  • Yeast Derivative Complexes. Other sources of organic trace elements that show promise are mineral enriched yeast. Presently the most common is selenium yeast with selenium complexed with a methionine molecule (selenomethionine). Chromium enriched yeast also has gained popularity for improving animal production (Rao et al., 2012).

Process of preparing of amino acid chelates of trace minerals

Amino acid chelates of trace minerals are prepared by chemical reaction using 2:1 molar ratio of amino acid preferably methionine and inorganic trace mineral ions. The basic process involved in preparing chelated mineral is depicted below.

Benefits of using organic trace minerals for livestock production

The positive effects of organic minerals on animal performance appear mainly due to higher bioavailability as compared to inorganic sources. There are several studies in different animal species with different sources of different mineral elements, which have revealed notable differences in the bioavailability of organic and inorganic minerals. There studies suggest that binding Cu, Zn, Fe and Mn with amino acids and peptides can enhance the bioavailability of these trace minerals, thereby leading to improved milk production, growth, reproduction and general health status in livestock.


Organic minerals have been shown to have beneficial effects under a wide range of applications in ruminants. These include higher production, increase in quality of milk, and higher reproductive efficiency. Trace mineral absorption and tissue deposition from some organic sources appear to be higher than from inorganic sources. A relative bioavailability value of Cu and Zn from Cu-methionine and Zn-methionine was found to be 33% and 52% higher than from inorganic copper and zinc sulphate, respectively in ewes (Pal et al., 2010). Many studies (Nocek et al., 2006; Griffiths et al., 2007; Siciliano-jones et al., 2008; Hackbart et al., 2010) have shown a positive effect on milk yield by supplementing cows with organic trace minerals in place of inorganic minerals. Cows fed organic trace minerals also have greater milk fat level than those fed inorganic trace minerals. With the same level of supplementation to cows: Zn (15 mg/kg), Mn (20 mg/kg) and Cu (10 mg/kg) from chelated sources resulted higher milk yield (11%), milk fat and protein percentages (both approx.7%) when compared with inorganic sources (El Ashry et al., 2012). Similarly in ewes supplemented with 40% less Zn from chelated sources (Zn-methionine) increased milk yield by 12% along with 26% and 31% increase in protein and fat production in comparison with inorganic zinc sulphate source (Hassan et al., 2011). The supplementation of 40% less minerals from chelated sources resulted in 4% increase in milk yield as compared with 100% inorganic minerals supplementation in cows at late lactation stage (Somkuwar et al., 2011).

Several studies have suggested that organic trace minerals improve various indices of reproduction in cows, including an increase in pregnancy percentage (Nocek et al., 2006; Defrain et al., 2009), a reduction in open days and services per conception (Kellogg et al., 2003), and a decrease in days to first postpartum oestrus (Campbell et al., 1999). Amino acid chelated trace minerals supplementation could decrease the open days by 42 days and services per conception by 42% when compared with supplementation of inorganic mineral sources because amino acid chelated sources of minerals increase the concentration of specific minerals in their uterine tissue. Therefore, supplementation of minerals through organic sources may be more effective in ameliorating the reproductive problems in ruminants.

Organic zinc is beneficial in enhancing resistance to mastitis because of postulated role of Zn in maintaining skin integrity and the keratin lining of streak canal. The udder health can be improved through reduction in somatic cell count in the herd by supplementing the organic mineral sources. Supplementation of Zn-methionine has resulted in 22% decrease in somatic cell count on feeding a lower level and 50% decrease in somatic cell count on feeding higher level of Zn-methionine (Table 1).

Table 1. Mineral proteinate supplementation and somatic cell count (SCC)

Form of proteinate supplemented Mineral supplied daily as proteinate (mg) Reduction in SCC (%) Reference
Zn 400 57 Harris (1995)
Cu Zn Se 100 300 2 52 Boland et al. (1996)
Cu Zn Se 100 300 2 45 Boland et al. (1996)
Cu Zn Se 100 300 2 35-52 at different weeks Boland et al. (1996)

Even though animals just need trace amounts of chromium to meet their optimal nutritional needs, it is not easy to meet the requirement due to poor bioavailability (0.4-3.0%) of inorganic chromium. Therefore, several organic chromium products, for example Cr-enriched yeast, chelated-Cr, Cr-picolinate, Cr-nicotinate have been developed that claim an improvement in biological availability of chromium. Recently, a number of studies suggested that supplemental organic Cr may be important in ruminant nutrition (Table 2), especially during stress conditions such as transit stress or early lactation stress. Among the most promising effects of supplemental organic Cr has been improved resistance to, or recovery from, stress and increased immune function. Improved health and growth performance are invariably associated with reduction in stresses for example stress of late pregnancy, calving and early lactation in dairy cow. No beneficial effects on performance of calves when given inorganic Cr from chromium chloride have been reported. On the other hand, several researchers have reported higher performance of calves with supplemental Cr as Cr-yeast, chelated-Cr during stress period.

Table 2. Effect of organic chromium on growth and lactation

Animal Cr source and level Effect on growth and milk yield Reference
Stressed calves Chelated-Cr 1 ppm 12.9% increase in ADG Mowat et al. (1993)
Beef steer Cr-methionine 400 ppb 800 ppb No effect on growth 2.8% increase in ADG Kegley et al. (2000)
Beef steer Chelated-Cr 3.3% increase in ADG Mathison and Engstrom (1995)
Steer Cr-methionine 400 ppb 5.5-11.4% increase in ADG Hong et al. (2002)
Periparturient dairy cows Cr-methionine 30 ppb 60 ppb 120 ppb 1.5% increase in milk yield 14.9% increase in milk yield 5.1% decrease in milk yield Hayirli et al. (2001)
Cows at early lactation Primiparous Multiparous Chelated-Cr 500 ppm 500 ppm 6.6-13.1% increase in milk yield 1.4% increase in milk yield Yang et al. (1996)

Source: Ohh and Lee (2005)

ADG, average daily gain

Pig and poultry

Dietary supplementation of trace minerals from inorganic sources with a large safety margin is a common practice in pig and poultry industry to prevent trace mineral deficiency. Pig diets are supplemented with excess trace minerals, often exceeding their physiological requirements. However, over supplementation of inorganic trace minerals often results in poor bioavailability due to trace mineral interactions with other components in the diet and can result in large dietary trace minerals being excreted in the faeces which can lead to soil and surface water contamination. One of the important strategies for reducing trace mineral concentrations in diets without affecting the animal’s performance is the inclusion of organic sources of mineral that have higher bioavailability and greater body retention than the inorganic form. Studies have shown that supplementing pigs and poultry birds with organic sources of minerals could have beneficial effect on pig and poultry performances.

Organic trace minerals have been used in broiler feeds, showing promise in improving live performance, bird health and meat quality characteristics. The most commonly used organically-complexed minerals include zinc, manganese, selenium, copper and iron. Significantly higher body weight gain, better feed conversion efficiency, higher tissue deposition of minerals and higher immunity have been observed in chicks fed diets containing same levels (100% NRC requirement of Cu, Zn, Fe and Mn) of inorganic and organic trace minerals (Abdallah et al., 2009), while laying hen performance and egg shell quality were found to be better in layers fed diets supplemented with Cu-methionine than those fed copper sulphate (Paik, 2001). Body weight gain was also higher in broiler birds fed diets supplemented with 0.5 ppm Cr from organic source than inorganic source (Mohammed et al., 2014). It has been found that Feed Conversion (FC) of chicks fed on diets containing inorganic minerals is significantly inferior (1.74) than chick fed diets containing 100% organic minerals, which recorded the best feed conversion ratio (1.63).

Table 3. Effect of organic chromium on poultry production

  Cr source and level Effect on growth and egg production Reference
Laying hen Cr-aminoniacinate 47 ppm 1.6% increase in egg production Piva et al. (2003)
Broiler Cr-methionine 200 ppb 400 ppb 11.5% increase in weight gain 2.5% increase in weight gain Ohh and Lee (2005)

In recent years, there has been a considerable reduction in the recommended levels of organically complexed minerals in broiler chicken diets without any negative effects on their performance (Bao et al., 2007; Nollet et al., 2008; Petrovic et al., 2009; Aksu et al., 2011a), antioxidant defense systems (Saripinar Aksu et al., 2010), hematological and biochemical parameters (Aksu et al., 2011b) and meat quality parameters (Aksu et al., 2011b). Broiler birds supplemented with organically complexed minerals at 25% of NRC requirement of trace minerals (Cu, Zn & Fe) have shown no negative effect on body weight gain and feed intake (Pierce et al., 2005). Using organic trace minerals with greater bioavailability does not affect body weight gain and has little effect on feed efficiency of broilers even when fed at 20% of the inorganic trace mineral level, and at the same time it reduces the environmental contamination due to lower excretion of minerals (Leeson, 2003). Replacing inorganic trace minerals with organic trace minerals (peptide chelate at the rate of 50% or 100%) improved performance and enhanced immune response of chicks (Ao et al., 2011). Organic minerals can be supplied to broiler diets at much lower levels than the current recommendations of inorganic minerals form without negative impact on broiler performance with decreased excretion of excess mineral.

Pigs fed mineral proteinates have been shown to gain weight at a higher rate than pigs fed the trace minerals solely from inorganic sulphates in the nursery phase (Creech et al., 2004). Some studies have shown a higher mineral retention of organic minerals, such as Cu-lys in weanling pigs (Apgar et al., 1995), Zn amino acid chelate in growing pigs (Susaki et al., 1999) and Cu and Zn proteinates in weanling pigs (Schiavon et al., 2000) than from their inorganic forms. In addition some studies have shown similar performance (growth) in pigs at lower levels of inclusion of organic minerals than inorganic forms commonly used. Based on several studies that attempted to evaluate the effect of replacing CuSO4 with different sources of organic Cu on weaning and growing pig performance, it can be concluded that at equal levels of inclusion, pigs fed organic forms of Cu have the same or even better growth rate and/or feed efficiency than pigs fed CuSO4. Also it has been possible to reduce pharmacological levels of inclusion of inorganic Cu by including Cu in an organic form without affecting pig performance. Feeding diets containing Cu-proteinate to piglets in the post-weaning period is able to maintain growth performance when 50-100 mg Cu was provided from Cu-proteinate compared with the level of 250 mg of Cu from CuSO4 per kg diet. Similarly, growing and finishing pigs could be fed 40 mg of Cu from Cu-proteinate, with similar performance to those fed 150 mg Cu from CuSO4 per kg diet.. Supplementation with 250 mg zinc-methionine (Zn-met)/kg diet (Ward et al., 1996) or 300 mg Zn-polysacharide/kg diet (Huntington et al., 2002) has resulted in weanling pig performance equal to that obtained using 2000 mg ZnO/kg. Replacing 15-36% of the inorganic minerals (Fe, Zn, Mn, Cu, Se and I) in the mineral premix with proteinate forms increased average daily gain (ADG) and gain: feed in weanling pigs (Veum et al., 1995). In growing and finishing pigs, feeding a diet containing all minerals (Zn, Fe, Mn and Cu) in the organic form (proteinate) at 30% of normal levels (36 mg Zn/kg, 39 mg Fe/kg , 18 mg Mn/kg and 7 mg Cu/kg), has shown faster growth rate compared with that on feeding the normal levels (120 mg/kg Zn, 130 mg/kg Fe, 60 mg/kg Mn and 20 mg/kg Cu) (Fremaut, 2003).

Table 4. Effect of pig performance on feeding diets containing reduced levels of minerals from organic sources

Parameters Inorganic (100%) Organic (100%) Organic (75%) Organic (50%)
Average daily gain (kg/d) 0.907 0.924 0.907 0.923
Average daily feed intake (kg/d) 2.22 2.29 2.26 2.27
Gain : feed 0.387 0.383 0.379 0.384

Source: Burkett et al. (2009)

Table 5. Economic efficiency of feeding minerals from organic and inorganic sources in pig

Treatment Relative economic efficiency*
100% Inorganic trace minerals 100
100% Organic trace minerals 94
100% Organic zinc 95
100% Organic copper 95
100% Organic manganese 95
100% Organic iron 95
50% Organic zinc 96
50% Organic copper 96
50% Organic manganese 95
50% Organic iron 96

Source: Abdallah et al. (2009); *taking economic efficiency of control as 100; economic efficiency as measured by feed cost/kg dressed weight

Organic mineral sources have relatively higher cost and this would limit the overuse of the chelates. Moreover, organic mineral sources are better utilized than inorganic forms. Recent studies indicated that supplementation of trace minerals in combination of inorganic and organic sources could give better results in terms of growth rate and immunity status of sheep (Gowda et al., 2014). Therefore, it is suggested to supplement the trace minerals to livestock as combination of inorganic and organic sources except chromium which could be supplemented through organic source only to obtain better performance.

Testing of chelated minerals

Simple methodology for verification of degree of binding of organic mineral compounds has not been available. There are varieties of tests which make subjective measurement of quality rather than chelation. The only way to verify that the product is an amino acid chelate is to look at the bonds that exist between the metal and the ligand. In this regard the Fourier Transforming Infrared (FT-IR) technique is comparatively more useful to test the chelation of the products.

Molecular Size determination of chelated minerals

Molecular size clearly plays a role in the effectiveness of an organic trace mineral (OTM) and provides a useful assessment as to a product’s potential efficacy. The protein based OTM is solubilised and then passed through a series of different size Millepore molecular filters. The Millepore filter is used to determine the molecular size and quantify the amount of each protein fraction in the product. OTMs passed through a 500 Dalton sieve filter are believed to be the best for maximum absorption. Metal content is also measured for each protein fraction to demonstrate the uniform bonding throughout the product. This procedure provides an objective measurement of OTM molecular size.

Test for solubility and structural integrity of complexed and chelated trace minerals

The advantages in bioavailability of minerals from complexes, chelated or proteinated (CCP) minerals supplements usually are attributed either to superior solubility or to the unique chemical structure of the compound or product. Manufacturers suggest that CCP are highly soluble, yet chemically stable and electrically neutral in the digestive tract and that CCP molecules maintain their structural integrity in the digestive tract, arriving at the absorptive sites in the small intestine as an original intact molecule. Therefore, solubility test in simple buffers (acidic and alkaline pH) and gel filtration chromatography to determine whether metals solubilised from the product are still complexed with amino acid or with other proteinous ligands, corroborated with free amino acid test using ninhydrin reagent along with metal determination by AAS/ICP-OES can be used (Brown and Zeringue, 1994).

Conclusions and applications

It is concluded that minerals from organic sources have higher bioavailability than inorganic sources. Livestock and poultry supplemented with chelated minerals have greater mineral utilization than from inorganic sources. The improved mineral nutrition from the chelate supplements leads to enhanced milk production, reproduction, and body condition compared with animals given minerals from inorganic sources. Organic minerals can be included at much lower levels in the diet than the current recommendations for inorganic minerals, without any negative effect on broiler birds and pigs. Using lower levels of organic minerals in broiler chicken and pig diets results in significantly lower concentration of minerals in manure, compared with birds fed conventional feeds formulated with inorganic minerals. Based on the findings it is suggested that the minerals can be supplemented in combination of inorganic and organic sources at two-third and one-third levels of requirements, respectively to obtain the maximum performance in animals and poultry birds. The trace mineral like chromium can be supplemented solely from organic sources because its bioavailability from inorganic sources is very poor.


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