Q: I understand that correct ratios of calcium and phosphorus are important to the function of muscle tissue during exertion such as in endurance racing. How does one achieve a good balance using imbalanced feeds? Is there a good strategy for mineral or electrolyte replacement during rest stops? –Michael

A: Calcium and phosphorus balance is indeed a complex topic. Active muscle uses ionized calcium for muscle activity. Since calcium (among other minerals) is also lost in sweat, maintaining appropriate levels of ionized calcium in the blood is one of the goals of feeding, supplementing, and training the endurance horse. A fit horse loses fewer electrolytes and minerals, including calcium, than the under-conditioned horse, and/or can better compensate for these losses.

In general, the less hand mixing of grains and supplements, the better. A commercial grain mix from a reputable company, along with good-quality grass hay, is usually the best way to go. Once you start mixing in oats and other cereal grains (which can increase the amount of phosphorus) or over-feeding alfalfa (more than about one-third of the roughage portion of the ration), achieving a balance gets more difficult. Providing free access to a granular mineral mixture containing calcium (12-10%), phosphorus (8-10%), salt, and trace minerals as the only source of salt (not blocks) helps ensure the horse is consuming enough of the critical sodium, chloride, calcium, and phosphorus needed for muscle activity.

Replenishing some of the minerals and electrolytes during endurance race rest stops is a good supportive strategy. Offering an electrolyte solution next to fresh water can restore some of the used minerals. Look for one with calcium, sodium, chloride, and glucose. Change the solution frequently, as bacteria can grow if the solution gets heated in hot weather