Ok-so I've been riding for 40 years, and teaching and training for 20. I have always based a horses' jump on his athletic abilities, scopiness, etc. I've seen the solid, 2'6 packers that can stretch to 3' but are better suited to the 2'6 job.
Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone.
Vitamin D facilitates active absorption of calcium and phosphate in the intestine through the actions of 1,25 dihydroxy vitamin D, which stimulates active calcium uptake by the cells lining the intestine. portion of circulating calcium is lost daily through excretion via the kidneys and the intestinal tract. Calcium lost from the body must be replaced from diet or supplementation to assure there is adequate calcium present for deposition of new bone.