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Cow Mineral Nutrition: Reading The Tag and Bioavailability

By Adele Harty
Mineral nutrition is vital to overall cow performance. Without an appropriate balance of minerals, cows may not perform as expected or could exhibit detrimental effects. There is value in analyzing your mineral program to determine if modifications need to be made to improve cattle health and performance.
Two recent articles discussed macro minerals and trace minerals and the roles they play in cow nutrition. This article will focus on reading mineral tags to ensure that the provided supplement is meeting the cow’s nutritional needs. Not all mineral supplements are created equal and it is critical to know how to evaluate a mineral tag.
Identifying Mineral Needs
The first challenge with a mineral program is knowing what the cow’s need. This is driven by the feeds and water they consume and it changes throughout the year. Oftentimes, mineral contribution from water may be ignored, but it is very important, especially when water could be high in salt and sulfates. Ideally all feeds and water should be tested for mineral content to determine deficiencies, toxicities and interactions. Once this is determined, mineral supplements can be sourced. Many companies have formulated minerals for specific regions or are willing to develop custom formulations for ranches. If you choose to use a mineral that has been formulated for a region, reading and understanding the feed tag becomes more critical.
Mineral Tag Analysis
There are a few key items to look at initially when analyzing the mineral tag. How much salt does the product contain? Products that contain 10% salt or more may not require additional salt and will result in an adequate daily intake of 3 to 4 oz. Mineral supplements that contain less than 5% salt are considered mineral concentrates with cattle consuming approximately 2 oz. per day. If using a mineral concentrate, free choice salt must be provided.
Next, take a look at the ingredient list to determine the type of mineral used in the supplement. Not all mineral sources have the same bioavailability to the animal. For example, you could be using a trace mineralized salt block that contains 300 ppm Cu in the form of copper oxide, which has a relative bioavailability of 15% compared to Cu sulfate which has a bioavailability of 100%. This means that there is only about 45 ppm Cu available in this product. On the other hand, if the 300 ppm Cu was provided as Basic Copper Chloride, which has a relative bioavailability of 196% compared to Cu sulfate, the bioavailability is 588 ppm Cu. A product with Basic Copper Chloride provides more Cu to the animal than a product with Cu oxide or Cu sulfate.
Mineral Sources
Trace mineral sources are divided into three groups: inorganic, organic and hydroxy trace minerals. Most mineral supplements will either contain all inorganic sources or a mix of inorganic and organic or hydroxy trace mineral. The challenge is knowing the proportion of the minerals in the mixes that contain more than one source of minerals.
Generally speaking inorganic minerals will be less expensive, but are typically less bioavailable than the organic and hydroxy trace mineral sources. There is significant variation within inorganics, with sulfates and chlorides being more available than oxides and carbonates. The exceptions to this are zinc oxide and magnesium oxide, both of which have a relative bioavailability of 100.
Organic minerals are those that are bound to an amino acid, protienate, polysacharride or other organic molecule and relative bioavailability exceeds 100. These sources are characterized as medium bioavailability with high cost. If animals are stressed or antagonists are present in large amounts the extra price paid for organics may be justified. Organic minerals will provide more value to cattle during weaning or other stressful periods, but the cost will likely exceed the benefits in a standard year-round mineral program.
Hydroxy trace minerals have a crystalline structure that protects the metal ions that are bound by covalent bonds to multiple hydroxyl groups. These covalent bonds allow the trace minerals to by-pass rumen digestion which increases bioavailability. These minerals have a high bioavailability with a medium cost and could be incorporated in high stress situations or as a portion of the trace minerals year-round. See Table 1 below for a sample of mineral supplements, mineral concentration, relative bioavailability and mineral availability.
Table 1. Mineral concentration and relative bioavailability of common mineral sources.
SupplementMineral concentration
(MC, %)
Relative Bioavailability*
(RV, %)
Mineral Availability
(MC x RV)
Calcium carbonate3810038.00
Calcium chloride3112538.75
Dicalcium phosphate2011022.00
Monocalcium phosphate1713022.10
Cobaltous sulfate2110021.00
Cobaltic oxide732014.60
Cobaltous carbonate4711051.70
Cobaltous oxide705538.50
Copper sulfate2510025.00
Basic copper chloride58196113.70
Copper oxide751511.25
(organic form)
Potassium iodate6910069.00
Calcium iodate649560.80
Ethylenediamine (EDDI)8010584.00
Magnesium sulfate2010020.00
Magnesium oxide5510055.00
Manganese sulfate3010030.00
Manganese carbonate463013.80
Manganese hydroxychloride44  
(organic form)
Defluorinated phosphate12809.60
Dicalcium phosphate188515.30
Sodium selenite4510045.00
Sodium chloride4010040.00
Sodium bicarbonate279525.65
Zinc sulfate3610036.00
Zinc carbonate566033.60
Zinc hydroxychloride55204112.20
Zinc oxide7210072.00
Zinc (organic form) 159 to 206 
*Relative bioavailability is the quantity or percent of the mineral that is absorbed. Relative bioavailability is expressed relative to the source listed first (italicized) for each mineral. A higher relative bioavailability shows greater absorption of the minerals by the cattle.
Adapted from: Ammerman, C.B., D.H. Baker, and A.J. Lewis. 1995. Bioavailability of Nutrients for Animals. New York: Academic Press; National Research Council. 1998. Nutrient Requirements of Swine, 10th revised edition. Washington, D.C.: National Academy Press; Mineral Supplements for Beef Cattle, University of Missouri Extension, Chad Hale and K.C. Olson, 2000; and Beef Cattle Mineral Nutrition, North Dakota State University Extension Service, Marcy Ward and Greg Lardy, 2005.
Salt Products
What about salt that has trace minerals added? There are multiple options for salt, but thankfully not as many as minerals. In working with producers, frequently the “blue cobalt” salt blocks are provided as the primary salt source to cattle. On multiple occasions producers have identified that these blocks are used to prevent foot rot, but Co does not play a role in immune function and likely is not helping decrease foot rot in the herd. Although cattle have a requirement for Co as outlined in the Trace Mineral article, the “blue cobalt” blocks may not be the ideal source of salt for your operation.
Due to the potential for iodine deficiencies in the Northern Plains, providing iodized salt is critical. This can be strictly as iodized salt or a trace mineralized salt, which will contain other key minerals such as Cu, Zn, Mn, and Co. Once again, read the label on these products to ensure the trace minerals are in a form that will be available to the animal. When salt is provided free choice, cattle will consume higher quantities in loose form compared to block form.
The Bottom Line
Working with a nutritionist to ensure that the appropriate mineral sources are used is vital to the efficacy of your overall mineral program. The mineral program needs to be evaluated to determine whether or not the needs of the cattle are being met.
For more information on mineral programs or custom mineral formulations for your ranch, contact Adele Harty at 605-394-1722