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.
Vitamins and minerals are substances that are vital inside the body to help it grow and become insusceptible to diseases. Some Vitamins are considered essential nutrients. Vitamin A is important for good eyesight, appropriate immune function and growth of tissues.