Trace minerals for animal nutrition
Essentiality and toxicity
On the contrary human beings, standard diets usually do not contain enough quantities of trace minerals naturally present in feed ingredients to satisfy the physiological needs of modern genetics of farm animals. So supplementation is practiced in routine in order to prevent any clinical deficiency. Adding trace minerals sources in the diet will fulfill the basic animal requirements for their maintenance, their growth and their specific needs for production (foetus, egg, milk, etc…).
Trace minerals are involved in many metabolic reactions. Animals in sub‐clinical deficiency may not show any external sign of symptoms, but however may have a reduced potential for performance and good health. Fine tuned supply of trace minerals to the animals enables to prevent this stage. A proper feed formulation in micro nutrients contributes to the productivity of the animal husbandry and production chain.
Edible animal products (meats, eggs, dairy products, offals, etc…) contain significant amounts of trace minerals which are essentials in the human diet. Well absorbed and metabolised sources of trace minerals are stored in organs and tissues. In some cases animal products can be enriched in some trace minerals, supplying naturally fortified sources of nutrients for human consumption. Other cases of potential effects of trace minerals formulation in animal diets include the interaction with lipid metabolism, thus mitigating cholesterol contents, or the reduction of oxidative degradation which may increase the shelf life of finished products.
Livestock wastes are by products of animal production but they can be recycled or utilised at their best value. In balanced vegetal and animal systems, their concentration in nutrients is profitable for crop production. Instead of consuming fertilisers manufactured with non renewable mineral resources imported from distant mines, farmers have the opportunity to give value to locally produced manure and litter from livestock and poultry.
Cases of toxicity may be acute, very rapid and severe, or chronic, without clinical signs which are easy to detect. Diagnosis may be possible with analytical measures on living animals, or on dead animals through an autopsy. To prevent excessive supply, scientific knowledge makes progress with better fine tuned definition of the nutritional requirements of animal categories. To handle micro nutrients as accurately as possible, premix and feed manufacturers must rely on sources of trace minerals with optimal physical and technological properties.
In geographical areas with intensive animal density, there can be increasing nutrient unbalance between animal excretion and uptake by the vegetal crops, thus resulting in potential accumulation in soils and waters. Some trace minerals like zinc and copper may be considered as heavy metals when present in excess in the environment. Some nutritional solutions exist in order to prevent this issue. The regulatory framework can limit the dietary contents in some metals, like the European Directive initiated since 2003.
Toxic when contaminated with undesirable substances
Because trace elements can be extracted from mines where undesirable substances are naturally present, some batches may contain too high levels of heavy metals (arsenic, cadmium, mercury, lead) and dioxins. Stringent regulation has started to be implemented to prevent contamination at the origin of the feed and food chain.
Trace minerals should be manufactured, transported and handled to avoid any harm to the environment and to human beings. These feed additives are incorporated at very low inclusion rates, for example 100 grams per ton of complete feed. Their particle size needs to be fine enough to ensure an homogeneous mixing in the feed, so that no animal suffers from nutritional deprivation, but without any dust which may be hazardous for the operators. Some of the essential trace minerals are irritant or even classified CMR. The occupational health is a growing concern in the feed industry.
It is now known that material properties at the nano scale are likely to change from bulk equivalents. Nanoparticles show new behaviour which create opportunities in many applications including the supply of highly bioavailable nutrients and molecules for living beings. In order to build the necessary level of confidence with this technology in the feed and food chain, we must address the gaps in the current level of knowledge on the physico‐chemical and ecotoxicological properties of these materials.