Mineral Nutrition in the Cow: Reading the Mineral Tag & Bioavailability

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.

Two recent articles on iGrow have discussed macrominerals and trace minerals and the roles they play in cattle nutrition. This article will focus on reading the mineral tag to ensure that the supplement you are providing your cattle is meeting their nutritional needs. Not all mineral supplements are created equal and it is important to know what to look for in a mineral supplement and what you might want to avoid.

Identifying Mineral Needs
The first challenge with a mineral program is knowing what your cows need. This is driven by the feeds they eat as well as the water they drink and it changes throughout the year. Oftentimes, we may not think about the mineral contribution of the water to the diet, 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 that may exist. Once this is determined, then 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.

Analyzing the Mineral Tag
As you analyze the mineral tag, there are a few key items to look at initially. How much salt does the product contain? Products that contain 10% salt or more don’t need 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 the recommended 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 sources of minerals have the same bioavailability to the animal. For example, you could be spending extra money for a high copper mineral, but the copper is being provided by copper oxide, which is only 15% bioavailable. Therefore, the mineral tag may show that the supplement has 5000 ppm Cu, but the cattle will only utilize 750 ppm (15%) because it is supplied as copper oxide. On the other hand, if tribasic copper chloride is a source of Cu, its relative bioavailability is 115 which means Cu is 15% more available to the animal than that in copper sulfate, which is used as the standard (100%). A product with tribasic copper chloride will provide more Cu to the animal than a product with copper oxide or copper sulfate.

Inorganic & Organic Mineral Sources
Mineral sources are divided into two groups: inorganic and organic. Inorganic will be less expensive mineral sources, but are also typically less bioavailable than their organic counterparts. Generally speaking inorganic sulfates and chlorides are more available than oxides and carbonates. The exceptions to this are zinc oxide and magnesium oxide, both of which have a bioavailability of 100. Chelated minerals are those that are bound to an amino acid or other organic molecule, and their bioavailability exceeds 100. If animals are stressed or mineral antagonists are present in large amounts the extra price paid for chelated minerals may be justified. Chelated minerals will provide more value to cattle during weaning or other stressful periods, but their cost will likely exceed the benefits in a standard mineral program. See Table 1. below for a sample of mineral supplements, mineral concentration, bioavailability and mineral availability.

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. This may be a situation where the “blue cobalt” blocks are being confused with the copper sulfate blocks, which are also blue. 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 salt blocks.

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.

Source: Adele Harty, South Dakota State University