Fertility problems in cows have been related to low phosphorus diets. Calcium and phosphorus are closely associated. There must be enough of each, but calcium should be equal to or greater than the phosphorus levels in a beef ration. Cows or other classes of cattle fed high-roughage rations are more likely to have a phosphorus deficiency than a calcium deficiency. This is because forages tend to be high in calcium but low in phosphorus.
Legumes are especially high in calcium, but cereal straws are low.
In contrast, grains are adequate in phosphorus, or nearly so, but deficient in calcium for cattle. Either one or both minerals may be deficient in beef growing or finishing rations, depending upon the ratio of grain and roughage. The requirement for sodium and chlorine is commonly expressed as the salt requirement. Sodium is the major mineral in fluids outside the body cells. Chlorine occurs both inside and outside the cell.