Mineral nutrition is one of the most complicated and least understood components of nutrition. For years, producers and researchers alike have known about the need for mineral supplementation; however, development of mineral supplements to meet the requirements of grazing cattle often becomes a difficult and challenging problem due to 1) changes in animal requirements with stage and level of production, 2) difference in forage supply of minerals, and 3) methods to supply cost-effective supplemental minerals that ensure adequate intake and bioavailability (Greene, 1999).

For most producers the place to begin development of a mineral program is simply identifying the animals’ requirements. It is important to recognize that, while published requirements are based on years of published research, our understanding of mineral nutrition in beef cattle is cursory at best. A growing body of research suggests that mineral requirements can vary significantly by breed, production, and the presence of antagonists. Producers should work with their nutritionist or Extension personnel to adjust their mineral program accordingly to account for these factors.

Mineral status can have a tremendous impact on the response to supplementation. If an animal’s mineral stores are adequate, it is unlikely that supplementation will result in a biologically or economically significant response. However, if an animal is in a deficient state, and production has been compromised, the response to supplementation can be dramatic.

The first step in determining mineral status of the cowherd is to objectively analyze various performance and production measures. If there appears to be a reduction in a particular measure, be sure to rule out other potential causative factors. It is also essential to evaluate the current mineral program. Is it well balanced? What percentage of the cow’s requirements does it meet? And, perhaps most importantly, are the cows consuming enough? The solution to the problem may be as simple as including a small amount of molasses to the mineral supplement to increase consumption.

The second step in determining mineral status is to determine how much of each mineral is supplied by the diet. Because of the inherent variability in the mineral content of the feeds and the potential error associated in predicting feed intake, this estimation can be challenging. Water also contributes a significant amount to the mineral nutrition of a beef cow. However, because of the extreme variability in mineral content and intake, most producers should only consider water as a source of potentially detrimental minerals (i.e. sulfur and iron).

The third and final means of assessing mineral status is to directly sample the animal. Mineral status can be evaluated by sampling and analyzing blood and/or tissue. For most minerals, a liver sample is the most reliable means of determining mineral status, especially for trace minerals. Mineral concentrations in blood are generally not good indicators of mineral status unless an animal is severely deficient. Liver samples can be obtained either post-mortem or from a live animal via liver biopsy. The liver biopsy procedure is simple and inflicts very little stress upon the animal. Consult your veterinarian or Extension personnel to find out more information on collecting liver biopsies.

Mineral sources can have a dramatic impact on the effectiveness of a mineral supplementation program. In general, inorganic sources are the most cost-effective means of supplying minerals to a beef cow. However, all inorganic mineral sources are not created equal. Research suggests that sulfate and chloride forms of various minerals are the most bioavailable, followed by carbonates, with oxides being the least bioavailable. One exception to this rule of thumb is copper oxide. When the powdered or granular form of copper oxide is included in a mineral supplement, it is a very poor copper source. However, research indicates that copper oxide needles, administered as a bolus, can be an extremely effective means of delivering copper to cattle on forage-based diets.

Organic mineral sources represent another option for producers to supply minerals to their cowherds. Research suggests that some organic mineral sources are indeed more bioavailable; however, production responses to supplementation have been extremely variable. Positive responses to organic mineral supplementation are most likely during stressful periods in the production cycle (i.e. calving and weaning), or when mineral antagonists (i.e. sulfur, molybdenum, iron, or aluminum), are present in large amounts. In these situations, producers should objectively weigh any expected benefit to animal performance against the added cost of including organic minerals in their supplementation program.

When evaluating a mineral supplement, it is extremely important to read the feed tag carefully to determine the guaranteed amount and source of each mineral. In some cases, a mineral source may be listed as an ingredient on the tag without a guaranteed analysis. In this situation, producers should err on the side of caution and assume that there is essentially no manganese in the mineral supplement.

Developing the most cost effective mineral program is certainly not a formula that can be applied to every farm and ranch around the country. Producers should carefully evaluate their production system, its resources, level of production, and production constraints, to develop the most cost-effective program for their operation. Keep in mind that more expensive mineral supplements do not always correlate with increased production or performance. Any cost associated with change in a mineral program must be accompanied by a corresponding increase in production or performance (i.e. weaning rate, weaning weight, etc.) to offset the added expense.