Trace  minerals are the minerals that are required in small quantities in animal nutrition. Some minerals are not required but may be associated with the minerals required for animals. The essential and non- essential  trace minerals may be toxic especially if present in large quantity.

The complexity of trace mineral in animal nutrition requires a thorough review of functions, interactions and availability of sources from time to time by the producer/ nutritionist. The trace minerals of primary concern also in poultry nutrition diets and recommended by the NRC (1994) include Zinc (Zn), Manganese (Mn), Copper (Cu), Iron (Fe).

Role of Trace Elements for Growth, Health and Reproduction

Selenium (Se) and lodine (I). Mineral  , though being a small part of complete poultry nutrition is critical for well being and performance of bird. In the past 25 years,  trace minerals role in immune function and related physiological roles have gained importance. New organic sources of trace minerals have been patented and marketed providing a more available form of poultry nutrition trace minerals for the chicken.

Even though the daily requirement of poultry nutrition trace elements is expressed in milligrams and micrograms, they play a vital role in various body functions like synthesis of Metallo-enzymes, Enzyme co-factors, Hormone production etc.

In Poultry nutrition industry trace minerals have a wide range of functions. It is important to understand these functions in order to better understand how these minerals affect animal growth and performance.

As described by Underwood and Suttle (1999), the functions of trace minerals in poultry nutrition can be broadly classified into four categories structural, physiological, catalytic and regulatory functions.

1. Structural Functions - Trace minerals in poultry nutrition can form structural components of organs and tissues, such as Zinc, which is a structural part of membranes and molecules.

2. Physiological Functions - Minerals are involved in maintaining osmotic balance, acid base balance, membrane permeability and tissue irritability in poultry nutrition.

3. Catalytic Functions - Of all the functions, these are the largest.  Trace minerals act as catalysts in enzyme & hormone systems and also serve as integral structural components of numerous metallo-enzymes.

These metallo-enzymes are required for a broad variety of metabolic activities such as energy production, protein digestion, cell replication, antioxidant activity and wound healing.

4. Regulatory Functions – In animal nutrition these are illustrated by the role of trace minerals in regulating cell replication and differentiation. While Zinc influences transcription, lodine as a constituent of thyroxine is associated with thyroid function and energy metabolism.

Need of Trace Minerals

Micronutrients in as trace minerals play a vital role in various metabolic, enzymatic and biochemical reactions ultimately leading to better growth rate, egg production and in overall poultry nutrition efficiency. Trace minerals have a very important role to play in the mechanism of nutrient circulation within the animal body. Deficiency or imbalance of any of these vital micronutrients for poultry nutrition results in deficiency symptoms, metabolic disorders, poor growth rate, low egg production, low hatchability and low poultry nutrition efficiency.

Absorption of  trace minerals in the intestine

For Poultry nutrition trace Minerals are absorbed in the intestine in ionic form. They are usually as inorganic salts, which get dissociated after entering the system. The free metal ion first gets attached to an organic molecule or "escort". Due to multiple antagonistic reactions of ingredients in the animal digestive system and limited ligand/ escort availability whatever minerals are able to find an escort are absorbed and the balance is excreted.

Supplementation through inorganic minerals

Selection of Trace Mineral Salts/Forms

Minerals find their use in various industries and also vary in the forms in which they are available. Hence, from a poultry nutrition standpoint, proper selection of the mineral salts is important. In poultry nutrition the following criteria play an important role in trace mineral salt selection

• Bio-availability

• Potency

• Availability

• Stability

• Purity

• Economics

In animal nutrition of these, bio-availability is an essential criterion, as highly bio-available forms are able to meet the birds' need, without much wastage. Purity of trace minerals is also important as these trace mineral salts are by-products of the chemical industry and normally do not undergo rigorous quality testing for purity. One of the most important factors to ascertain prior to formulation is the state of hydration of a mineral. Many minerals forms contain bound water which obviously dilutes effective mineral concentration.

Example: lodine is the most reactive element. Potassium lodide, stabilized Potassium lodide, Potassium lodate, Calcium lodate and EDDI are the sources widely used for supplementing iodine in  poultry nutrition.

In poultry nutrition trace elements in amounts exceeding animal requirements is widespread, probably because it is inexpensive, unlikely to harm animal and may be beneficial. It is desirable to identify maximum bio-available elements necessary to support peak performances.

Trace mineral sourcing

Trace minerals are available in a variety of forms and periodically problems arise due to lack of knowledge of the composition and/or stability of salts.

Poultry nutrition supplementation of minerals to animals above requirements/needs is also a common practice as a safety margin to prevent any likelihood of deficiencies. If any mineral in poultry nutrition is supplemented or present in ingredients at levels higher than the need of animal it may negatively affect the availability and absorption of other minerals.

The general guidelines for analytical parameters for selected mineral salts are as follows:

Physical Properties:

• Color

• Density

• Odor

• Texture

• Particle size, distribution. Flow ability

• Hygroscopicity

• Uniformity

• Foreign matter and molds

• Lumpiness

• Compressibility

Chemical properties:

While analyzing the trace minerals, international standard analytical methods like AOAC (Association of Analytical Chemists) AOCS (Association of Oil Chemical Society), BP (British Pharmacopoeia) and USP (United States Pharmacopoeia) are utilized. Some of the parameters being analyzed and studied are: .

• Bio-availability

• Stability

• Inherent characteristics of the salt

• pH

• Purity

• Electrostatic charge

• Potency

• Heavy Metal Content

The animal nutrition product manufacturers are often concerned about space in the diet whilst designing during formulations. There is trend towards making very concentrated mineral and vitamin premixes to try and optimize on the space availability. In considering concentration of mineral source, oxide appears attractive, since they invariably contain the highest mineral concentration. Oxides however are potent oxidizing agents and if stored with premixed vitamins for any length of time, can cause destruction/ deterioration of vitamins that are susceptible to oxidation.

Different class of poultry require different levels of trace minerals

In the Indian scenario, it is observed that the trace minerals do not get due respect whilst formulating diets in the poultry nutrition industry. Many of the trace minerals manufacturers tend to formulate trace minerals in general and do not consider the different requirements of broilers and layers. The requirement of each type of poultry nutrition is different as they represent distinct categories with entirely different needs.

Need for organic minerals

Inorganic sources of trace minerals are efficiently absorbed and utilized up to a point. Beyond a certain level inorganic supplementation of trace minerals does not evoke a positive response. Hence beyond a certain level of supplementation, organic forms of the essential trace minerals should be incorporated in a ration in order to maximize animal performance. Organic minerals have shown specific target tissue response, so they are bound to pronounce better result/ response. As organic minerals are absorbed more effectively with an advantage of better results at lower usage level. For overall benefit in poultry nutrition giving supplemental trace mineral sources that are readily bio-available to the animal will, further, allow for a lower inclusion rate in the diet and thus minimize mineral losses in animal excreta.

here are six types of organic trace minerals available in the market. They are as follows:

1)      Metal amino acid complex

2)      Metal specific amino acid complex

3)      Metal amino acid chelate

4)      Metal proteinate

5)      Metal polysaccharide complex

6)      Metal propionate

In order to achieve optimum and desired performance in poultry nutrition supplementation of trace mineral in right and sufficient quantities is crucial.

How do we achieve improved mineral status?

1.      To supplement the entire requirement through inorganic forms of trace minerals at high levels.

In animal nutrition to meet the increasing need for trace minerals to cater the growing production needs for poultry, the industry has steadily been increasing the quantities of inorganic trace minerals in the diet. Whether these high levels will fulfill the required optimum trace mineral status is a question mark. Various researchers have described the negative impact of high level of inorganic minerals, due to their interactions and competition for absorption sites. Apart from this, higher level of minerals in the diet will have a serious impact on environment in terms of variable excretion of trace minerals in the excreta.

Mineral Interaction

The most common antagonism occurs between Zinc and Copper, as both compete for the same binding site during absorption. High levels of dietary Zinc will inhibit Copper absorption, hepatic accumulation and deposition in the egg. Ratios greater than 4:1 of Zinc :Copper can be considered antagonistic. High levels of Calcium, Copper and Iron can interfere with Zinc. Excess dietary Phosphorus will interfere with Manganese availability in poultry nutrition. High Manganese increases lodine excretion and reduces Iron absorption. Excess Calcium andPhosphorus inhibit Manganese absorption. Iron and Cobalt slightly reduce Manganese availability. In poultry nutrition These interactions can be reduced by supplementing a portion of the mineral requirement through chelated minerals, which are protected from interactions and have better bio-availability.

2. To supplement the total requirement of trace minerals in organic form.

Whereas organic minerals may be absorbed more readily, the option of providing the entire requirement of trace minerals in an organic form is an option that is very expensive. To counter the pricing challenge, several producers of organic trace minerals recommend their products at very low levels which, often, depress production specially in the long run.

This matter is further aggravated by the availability of sufficient forms of organic trace minerals with varying bio-availability.

2.    To supplement trace minerals in a combination of both organic as well as inorganic forms.

It is observed that inorganic trace minerals in poultry nutrition exhibit an equally good or better bio-availabilitythan organic minerals especially at lower levels of supplementation; hence the majority of the required optimal levels can be achieved by adding bio-available forms of inorganic minerals procured from a reliable source. To achieve a still higher mineral status in the bird, which may not be possible by inorganic minerals for reasons explained above the same can be fulfilled by adding appropriate forms of organic/ complexed minerals.

Conclusion

Trace minerals play a vital role in poultry nutrition. The requirements of different segments of poultry, selection of the salt, and the quality of the trace mineral used are areas that warrant attention. Further, the bio-availability of inorganic minerals to the bird is limited due to natural factors; hence the role of organic trace minerals to improve mineral availability in high producing birds may be examined to provide a viable solution to trace mineral  in modern day poultry farming.