Aspects of using chelated trace minerals in cattle feeding


By Susanne Rothstein, Biochem Zusatzstoffe Handels- und Produktionsgesellschaft mbH, Germany


Trace minerals are essential in all animals for a wide variety of physiological processes. They carry out key functions in relation to many metabolic processes, most notably as catalysts for enzymes and hormones, and are essential for proper health status. The native levels of minerals in feed materials, especially in forages, can be highly variable as a result of many factors such as plant age, soil, fertilization practice, species, variety, seasons, and grazing pressure. For example, the content of trace elements decreases sharply with increasing crude fiber content. For cattle, the elements copper, zinc, manganese, cobalt, iodine and selenium are the most important, recommended to be provided via feed additives in mineral supplements and concentrates in order to fulfill requirements (Table 1). The native concentrations of these trace minerals in feed materials


are often not enough or not bioavailable in an adequate amount to cover the animals’ demand in modern production systems. From 2015 to 2018 the concentration of zinc in silage was typically below the recommended level of 50 mg per kg dry matter (GfE, 2001) and analyzed samples showed high variations between and within years (Figure 1). That’s why it is often recommended to analyze forages for trace minerals, as far as the native content is considered for formulating the mineral content of feed.


regeneration after calving, environmental and physiological stress. If the diet does not provide adequate amounts of trace minerals,


body reserves of the animals are impaired. In case of subclinical trace mineral deficiency non-specific symptoms such as reduced fertility, lowered milk yield, increased mastitis incidence, reduced growth rate or increased claw problems could occur in cows. An assessment of the trace element status of the animals, based on blood or hair analyses, as well as feed and water analyses, can help to reveal both primary and secondary deficiency situations. Due to the changing requirements during the production cycle and differences between individual farms and animals, the implementation of an adequate supply of trace minerals is a challenge. Although the requirements can be roughly estimated by the sum of demand for maintenance plus trace minerals needed for growth performance and milk production, it is difficult to estimate the true demand of the individual animal. When defining the requirements of high-yielding cows, the official recommendations often do not fit any more with challenging production situations and do not consider special health effects of some trace minerals. One example would be the positive effect of increased absorbable zinc levels on the reduction of somatic cell count in the milk, which is partly explained by positive effects of zinc on teat canal keratinization. Absorption is affected by many factors, which makes it difficult to


Figure 1: Average native zinc content in grass and maize silages 2015 – 2018 (adapted from LUFA, Northwestern Germany, Annual reports 2015-2018)


European feed law allows a wide range of trace mineral additives


to be used in cattle nutrition and also regulates the maximum inclusion levels in the final feed. Because of environmental concerns the maximum allowed inclusion levels of some trace minerals have been reduced several times during recent decades. On the other hand, the following situations and factors are known to increase the demand for trace minerals in growing and breeding cattle: teat canal keratinization,


PAGE 32 NOVEMBER/DECEMBER 2019 FEED COMPOUNDER


predict the true absorbable amount of dietary trace minerals from native and feed additive sources. Firstly, physiological influences like type and age of animal, gestation phase, trace mineral status, health level, or the intestinal milieu play an important role. Secondly, diet-related factors like antagonisms, feed composition or feed treatment must be considered. It can be assumed that in almost all feeding situations several antagonists, are present and interfere with absorbability of trace minerals. A well-known example is secondary copper deficiency either caused due to high levels of iron in drinking water or from increased concentrations of sulfur and molybdenum in feed. Finally, the trace mineral source itself affects absorbability due to differences in valency state of the metal, dosage level, and the chemical binding form. Depending on the specific chemical characteristics, trace mineral sources differ in solubility, pH interactions, and finally in their availability for absorption. Differences in bioavailability between several binding forms have been documented in vivo. Reviewing the literature, native trace minerals are assumed to be of low bioavailability. Sulfates are seen as beneficial compared to oxide forms, and organically (chelate) bound forms allow a higher absorbability of Zn, Mn, Cu, and Fe status than the inorganic forms. Since the 1990’s several categories of chelates of zinc, manganese,


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68