By multiplying the percent of diet dry matter in hay times the percent of the mineral in diet dry matter, we can compare what is being supplied to the requirement. Supplemental magnesium in sources such as magnesium oxide, magnesium sulfate, and magnesium carbonate are absorbed at approximately 70 percent. Magnesium deficiency is most often seen in the spring. Signs include muscle tremors, nervousness, and possibly death. It should be noted that our forage analysis has a potassium content of 2.23 which is slightly high and can further reduce magnesium absorption.
Potassium deficiency is rare in horses.
Forages are good sources and can easily meet the requirements of most horses. Good supplement sources include potassium chloride and potassium carbonate. In this case, the forage will provide an excess amount of potassium. Sodium helps to regulate acid-base balance and fluid movement across the cell membranes. However, the hay will not meet our requirements, and the grain source is most likely low.