by: Stephen B. Blezinger
Ph.D., PAS

Part 1 -- INTAKE

Mineral nutrition, in general, has been studied at great length and for the most part a great deal is known about the importance of minerals in cattle nutritional programs. It is not, however, a topic that appears to be readily understood by many producers, researchers or ag professionals. This is evidenced by the number of products on the market and the wide range of formulation differences and pricing structure. Over the next few issues we will discuss mineral supplementation and attempt to analyze the many variables that come into play when considering a particular mineral supplement or program. We will start off with intake. From there we will cover product formulation, mineral “bioavailability” and effectiveness of weather coating. Hopefully by the end of the series we can shed some light on the many variables and factors that have a role in the effectiveness and value of mineral supplements.

Mineral Intake – one of the biggest challenges

Intake of minerals falls into a couple of categories. One is the amount the producer wants the animal to consume and is generally related to production cost. Mineral supplements can be expensive. As such in many cases the producer wants the animal to consume as little as possible in an effort to keep his costs down. This is not a particularly effective viewpoint since in many cases this may prevent the animal from consuming the amount of mineral actually needed to meet its requirements.

Another key problem that can reduce the effectiveness of a mineral program is variability of intake of free-choice mineral supplements. This intake variation occurs in two ways. One, intake by individual animals within a given herd over a given period of time. It is accepted that within a given group of animals, observations of individual mineral intake will fall into a typical bell-curve plot (Figure 1) common to population data observations in other biological systems.

These intake data, when broken into 1/3s result in fairly general observations over a given herd of animals. Approximately 1/3 of the group will eat less than the targeted intake, 1/3 will eat within an acceptable standard deviation of the targeted intake and 1/3 will consume more than the targeted intake. The results of these individual or group intake patterns when viewed from an overall perspective, might lend the observer to believe that the herd, in general, is consuming appropriate levels of mineral, when, in fact, a full 1/3 may be consuming mineral supplements at a level below that required to maintain an appropriate status of many if not all required minerals. This can be especially detrimental in terms of the trace minerals which are required and fed within a very small window to begin with. For instance, the Beef NRC (2000) indicates the recommended daily requirement of Selenium to be .1mg/kg of overall daily dietary intake. Most diets are formulated at higher concentrations that this. However, given the small required level, even small deviations in supplement intake can result in under or over consumption of Se.

The animals that may be consuming little or no supplement are obviously at risk for diminished mineral status and may experience a variety of related health and performance issues. Over time this could potentially affect their longevity in the herd. In many cases there will be animals observed to be the “problem” animals in the herd – they don't breed as well, they have more health conditions requiring treatment, etc. The goal here is to minimize the number of cattle which fall into this group although the producer has to accept that there will always be a few.

The second issue here is the group of animals that may be consuming excessive supplement. These animals can likewise experience health and performance issues but due to excessive mineral intake levels or interactions or antagonisms caused by excessive levels. Again, the goal is to minimize the size of this group.

Another measure of intake variability can be noted over periods of time. Figures 2, 3 and 4 below illustrate this fact. These data were collected by a major nutrition company (Vigortone Ag Products a subsidiary of North American Nutrition and Provimi International) who are primary in the manufacture of mineral supplements.

Figure 2 compares the intake mineral supplements provided to cattle while grazing warm or cool season grasses from spring through fall. While intake patterns are similar, mineral intake on cool season grasses are about 31 percent lower than consumption on warm season forages. This means that if the mineral supplement is the same in both instances the intake of all nutrients will also be reduced by this amount.

Figure 3 illustrates intake data collected in a ranch trial in South Dakota over a two year period. Initially intake levels were very high and reflect a cow herd that has previously been on a very poor mineral program or none at all. After about two months, mineral intake decreased to a more normal level (target intake of 4 oz. per head per day). However, over the subsequent 20 months, intake ranged from a low of .75 oz/hd/d to 4.93. Low intakes coincided with the spring of the year when grasses are higher in quality and quantity. Mineral intake is commonly affected by forage conditions. Normally, in most areas, as forages flourish, mineral intake will decline.

Finally, Figure 4 illustrates data from yet another intake trial run in Iowa. In this trial intake over 6˝ month trial period ranged from 2.0 to 14.0 oz/hd/day. Again, target intake was 4 oz/hd/d resulting in intakes of mineral supplements ranging from 50 percent to 350 percent of target.

Similar variability has been noted in different studies across the United States (although intake patterns may differ). The net result of this variability is a potentially dramatic variation in the status of critical minerals, often resulting in impaired reproductive, gain or health performance.

Practical Observations

When evaluating intake a number of observations may be made.

1) Intake is affected by a variety of factors which may include:

a. Palatability of the supplement (formulation issue).

b. Tendency of the product to get hard or set up in the field (formulation issue).

c. Time of year/quality, quantity forages.

d. Production status of cows. Cattle nursing large calves will consume more, calves will also consume mineral.

e. Placement of mineral feeders. Feeders placed close to water, resting or shade areas will exhibit higher intakes. Feeders placed in remote or isolated areas will exhibit much lower intakes.

f. Availability of other supplements. Feeding other supplements will reduce mineral intake and may conflict mineral status if mineral content of ALL supplements is not considered.

2) Per the discussion above, intake will fluctuate greatly over a period of time. Intake evaluation must take place over an extended period (one month minimum, three months is better, six months better still and so on).

3) When changing mineral supplements it is not uncommon for intake to change (up or down) dramatically until the herd becomes acclimated to the new product. This often takes one to two weeks.

4) Intake is much more consistent when mineral supplements are kept available. Mineral feeders should be checked regularly (weekly) to insure supplement is available. Allowing cattle to run out will tend to increase the “erraticness” of intake.

5) Mineral supplements that are palatable and are consumed properly will exhibit less tendency for hardening since cattle continually disturb the supplement. However, even the best products may experience some hardening from time to time.

6) Mineral supplementation takes MANAGEMENT. It is not just a matter of dumping supplement into a feeder and forgetting about it. It may take movement of the feeder from time to time, changing the supplement to adapt to different forage, production period or environmental conditions.


We know definitively that intake of mineral supplement can vary significantly for a host of reasons. These include individual animal preference or behavior, forage quantity and quality, time of the year, feeder management, quality, formulation, palatability, etc. of the supplement itself. Obviously some of these factors are out of the producer's control. However, when circumstances such as environment and forage conditions change, it is important to understand how we must mediate these situations by changing management, product type or characteristic.

It is also important that we carefully monitor mineral intake and scrutinize the supplement we are using. Seldom will the same product work continuously in all conditions. Since the herd's health and performance is so closely tied to mineral status it is critical that this aspect of your nutritional management program be attended to carefully.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached by phone at (903) 352-3475, by mail at 667 CR 4711 Sulphur Springs, TX 75482 or by email at

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