Updated: May 8
About 99% of the calcium in a horse's body is contained in bone. The remaining 1% moves about controlling the conduction of impulses along nerves, contraction of muscles, and a myriad of other functions. The big problem is that, in order for life to continue, the level of calcium outside your horses' bones has to be maintained within very narrow limits. If the horse's calcium intake is inadequate for even a day, then the horse's body cannibalizes its own skeleton to make up for the deficit.
Optimal bone strength is essential for all performance horses. Look what happens with so many horses on the road to top events (ex. Kentucky Derby). Horses get stress fractures, and all the training and hope go out the window. Stress fractures from weak bones are almost an epidemic in performance horses. The first step to combat them is to get your calcium nutrition right.
You should supplement the calcium at night because calcium flux in the body is greatest during sleep. As Mom says, milk before bed does build strong bones.
Bone is fascinating stuff. Unless you continually stress it, the structure disintegrates, And if you stress it in only a particular direction, all the new molecules grow and align themselves only in that direction to resist the stress. The heavier you stress bone in all directions without breaking, the stronger it gets. But only if you have all the necessary elements available in the blood to build it.
Just to remind you, calcium by itself won't build a molecule of bone. To use calcium, the horses' body has to have adequate supplies of at least, magnesium, silicon, fluoride, zinc, copper, boron, manganese, phosphorous, and vitamin D. This multi-nutrient synergy is essential for bone growth which is so critical for performance horses.
Performance horses may be doubly calcium deficient because bone mineralization increases tremendously in response to the stress of exercise. This increased density of the bone requires greater calcium intake in order to make it. Mares are especially vulnerable because their bone metabolism is always on the edge of disaster. Amenorrhea caused by the detrimental effects of intense exercise on hormone imbalance, occurs in up to 40% of top mares and fillies. Unless mineral intake is absolutely optimal this hormonal imbalance causes significant excretion of body calcium cannibalized from their bones. The high protein intakes of many performance horses' also cause increased excretion of calcium, often resulting in a negative calcium balance.
Measurement of calcium status is difficult. The usual measure on a blood screen, serum calcium, is useless for performance horses. The body can continue to live only if calcium in the blood is kept within narrow limits. Because survival is more important than strong bones, in otherwise healthy performance horses', the body will pull calcium from the bone into the blood to maintain blood calcium levels until the skeleton collapses. So your serum calcium can remain within normal limits even with minuscule calcium intake.
There is some recent evidence that calcium supplements can be ergogenic for both anaerobic and endurance performance. Dr. J.T. Richardson and colleagues found, in horses, that calcium supplements prolonged time to exhaustion. Given the high incidence of calcium-deficient diets and high calcium demands of exercise, it is likely that such ergogenic effects simply reflect the correction of imbalanced mineral status in the body. Remember, don't just supplement calcium, go for the whole enchilada!