Microminerals in dairy cattle nutrition

24-06 | |
Selenium is considered an essential mineral in immunity, especially in the transition phase (three weeks pre- until three weeks post-calving). Photo: Anne van der Woude
Selenium is considered an essential mineral in immunity, especially in the transition phase (three weeks pre- until three weeks post-calving). Photo: Anne van der Woude

No one disputes the need to supply a vitamin-mineral supplement, but there is much debate over the level of intake and the sources of minerals to be used.

The elements of greatest nutritional interest are zinc, copper, manganese, cobalt, selenium, iron, and iodine. They fulfill the function of enzyme activators or cofactors, participate in oxygen transport, and regulate microbial enzymes. Additionally, they play a very important role in fetal development, reproductive function, and immune activity.

  • Zinc is found in higher concentrations in the skin and horn tissue and has a fundamental role in maintaining the integrity of cell membranes. It is important for the health and productivity of the cow, especially in the mammary epithelial cells that coat and line the surface of milk ducts.

  • Copper is involved in energy metabolism, the maintenance of nerve function, reproduction, and in immune function. Copper participates in the synthesis of hemoglobin and collagen – the maintenance of bones and cartilage.

  • Manganese, also essential for the production of bone and cartilage, influences the incidence of hypocalcaemia (low level of calcium in the blood) during peripartum, and facilitates the nesting of the embryo at the beginning of gestation.

  • Cobalt, a component of vitamin B12 (cyanocobalamin), participates in the synthesis of the amino acid methionine. A cobalt deficiency affects fat metabolism.

  • Selenium is considered an essential mineral in immunity, especially in the transition phase (three weeks pre- until three weeks post-calving). It is involved in the metabolism of thyroid hormones. A member of selenoproteins, within which glutathione-peroxidases act synergistically with vitamin E – selenium prevents the accumulation of free radicals and peroxides at the cellular level.

  • Iron, found in all cells of the body, acts as an oxygen carrier in hemoglobin and myoglobin.

  • Iodine, fundamentally located in the thyroid, intervenes in the regulation of cellular oxidation, protein synthesis, reproduction, and fetal development.

In addition to aiding metabolic functions, these trace elements act as micronutrients for the microbial population of the rumen, therefore increasing the value of manure and livestock waste, allowing the use of chemical fertilisers to be reduced.

The difference between inorganic and organic mineral sources

For some minerals there is only one authorised inorganic source, as is the case of iodine and selenium. For others, such as zinc, manganese, and iron, there is the possibility of using different sources.

Minerals sourced inorganically (i.e. from oxides, sulphates, hydroxychlorides) have numerous absorption interferences with each other. In general, intestinal absorption of inorganic minerals is low.

Minerals sourced organically are generally chelates from hydrated amino acid, glycine chelates, amino acidhydroxy analogs, protein hydrolyzate; or selenomethionines produced by yeasts (the only organic form of selenium authorized by European legislation). The main advantage of organic mineral sources, compared to inorganic ones, is that they avoid absorption interference with less risk of saturation.

Suggested amounts of microminerals in feed

The real difficulty lies in defining what the optimal dose is, and this will depend on the mineral source, the requirements of the animal, and the contributions of the raw materials. As we have seen, it is not easy to precisely establish the level of absorption of each mineral by the animal. There are 4 basic types of animals to consider:

  1. Calves until the complete functional development of the rumen

  2. Calves and heifers for rearing

  3. Dry cows and calving

  4. Lactating cows

Based on research from the US National Research Council, 2001; French Institut national de la recherche agronomique, 2018; W. P. Weiss; Ohio State University, 2017, Table 2 indicates the suggested minimum supply of trace elements that should be supplemented based on productive state. But even within these groups, needs are dependent on productive level and stress factors to which they may be subjected.

Trace elements must be specially manufactured and handled to avoid any harm to the environment or to humans. Some are merely irritating substances, but others are classified as classified as CMR (carcinogenic, mutagenic or toxic for reproduction). In areas with high animal density, there may be a nutrient imbalance between excrement and the absorptive capacity of plant crops, resulting in accumulation in soil and water. Zinc and copper, for example, can be considered heavy metals when they are present in excess.

Karen Willoughby Freelance journalist
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