A mineral supplementation program should simple, economical, and meet the needs of the cow herd as they change from one phase of production to another, and as they change diets (grazed pastures to harvested forages). These kinds of strategies have a good chance of being implemented.
Calcium and P are probably the two minerals that most cow/calf producers should focus on especially when feeding harvested forages and before and during the breeding season.
Phosphorus is the most expensive mineral that is supplemented. A time tested, cost effective mineral program, has been a program that is ½ dicalcium phosphate (dical): ½ salt. Always have salt available for the cow herd. Some producers have included a trace mineralized salt in some situations when using dical. If the diet has a good phosphorus source, the formula may be 1/3 dical: 2/3 salt.
DO NOT over feed phosphorus. If you are in a situation where trace minerals are needed, there are commercial mixes available. Feed only what is needed and not supplied by the diet.
As micro-minerals are added to the mix, the cost will increase. In addition, as more of the minerals in the mix are in the chelated form versus the inorganic form, cost will go up. Read the tag for the levels that should be consumed by the cow on a daily basis. For most mineral supplements and the self-mixed mineral supplements mentioned above, 2 to 3 oz/head/day is a typical intake.
Finally, if your cows graze pastures in the spring-time where grass tetany is a problem, supply a mineral that contains magnesium oxide. Begin this supplementation at least 30 to 45 days before grazing these pastures.
Magnesium is not very palatable, so these supplements contain ingredients that will entice them to consume the mineral. Read the tag to determine what daily consumption should be. Most grass tetany mineral programs will require cattle to consume 6 to 9 oz/head/day. Over supplementation of K can trigger grass tetany.
By Dr. Rick Rasby, Professor of Animal Science
Beef Cattle Production Timely Topic
University of Nebraska - Lincoln / Institute of Agriculture and Natural Resources