Typically in situations where cows or stocker cattle are grazing or being fed harvested forages, the calcium requirements (0.2 to 0.4 percent) are met. An exception to this would be cows placed on a high grain diet during periods of drought. In these instances, calcium should be supplemented.

In contrast, phosphorus (14 to 28 grams per day required) may be deficient in some grazing situations. Table 1 lists the phosphorus requirements of 1,200-pound cows as influenced by a number of factors.

Table 1: Phosphorus requirements of 1,200-pound cows as influenced by a number of factors

Stage of Production Minimum Daily Phosphorous Requirements,
Grams
Pregnant:
Mid Stage 17 grams
Late stage 20 grams
Lactating:
10 lbs./day 22 grams
20 lbs./day 27 grams

Know the quality of the forage that the cattle are consuming. Depending on maturity of the forage and stage of production of the cattle, little to no P supplementation may be needed.

Phosphorus is expensive, so don't over supplement it in a mineral program.