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 Inhibits Calcium. Vitamin D, a vitamin your body produces when stimulated by the ultraviolet rays of the sun, plays a vital role in calcium absorption. You body needs calcium to build strong bones and to promote muscle contraction, nerve transmission, hormone secretion and vascular function.