Before worrying about the ration of calcium to phosphorus, first be sure the diet has the required amounts of both minerals. Once the diet is properly fortified, the ratio of these 2 minerals becomes important. For growing horses calcium to phosphorus ratios may range from 1.2:1 to 3:1. Outside of this range growth disorders can occur. For mature horses, the calcium to phosphorus range is less critical. A range of 1.1:1 to 6:1 is considered safe. Make sure the amount of phosphorus never exceeds the amount of calcium in the diet.
